Rhonda Patrick: I'm delighted to be sitting here with Luke van Loon, who is a professor at Maastricht University in Netherlands. He is well known for his significant contributions in the field of exercise and nutrition, particularly looking at how protein metabolism affects muscle adaptations, how exercise affects protein turnover. I'm very excited to have a discussion with you today, Luke. Maybe we could start at the beginning–why protein is important, why we need protein.

Luc van Loon: So it's interesting to realize that all tissues, all living tissues, so also skeletal muscle tissue is constantly being synthesized and broken down. And that is always hard to imagine that every tissue in your body is breaking down, building up again. So all the constituents are constantly being renewed, re-mobilized, refurnished. And so for muscle, that happens at a rate of one to 2% per day, which means that in, say, 50 to 100 days, you have completely renewed your muscle. And so that renewal is actually one of the factors that makes it able to adapt to its use, to become bigger if you become a bodybuilder or become smaller when you actually don't move around anymore. So that dynamic, that is why we. Yeah, that is what tissue is. And that tissue requires constant renewal. And therefore, it needs protein, or at least the building blocks of proteins, being the amino acids.

Rhonda Patrick: So there's protein requirements that have been established by a variety of committees, World Health Organization, and those protein requirements are generally 0.8 grams of protein per kilogram body weight. Can you tell people what evidence that those requirements were established on or how that was based, where it came from?

Luc van Loon: Yeah, that's always. That is a lecture on itself. So, in the past, people did a lot of nitrogen balance studies. So amino acids contain nitrogen, and so nitrogen goes into the body as protein, and nitrogen also leaves the body as nitrogen, but then as urea or in the urine. And so measuring the balance between what goes into the body and what leaves the body gives a nice way of seeing whether you're in a positive balance, a negative balance, or neutral balance. So what they've done in the past is basically give people a low protein content diet for one or two weeks, a moderate or a high amount of protein, and then see whether they become in a positive or negative balance. And the assumption is, if you're in a neutral balance, it's good. And if you actually give a low protein diet, you go down to 0.66, then you actually can stay–and most people actually stay–in a neutral balance. And then they suggest that with some leverage on top, we actually get to the 0.8 grams. But that is, I regard that as a minimal requirement to stay in balance on the diet that has been provided for one to two weeks. And that's a little bit an issue because, first of all, there's some methodological issues with nitrogen balance. It's difficult to really figure out how much nitrogen goes in because people always underreport what they're eating. And the second part is there's also some nitrogen leaving the body that you don't measure, for example, in air or via the skin. So that's already an issue. But the other thing is the body can adapt to more or less protein. So being in a certain balance doesn't guarantee that that is actually your requirement or your optimal requirement. And that's where all the discussion comes from. Because, as I said, if you have your muscle turning over and you give it less protein, the turnover will actually go down. Is that a good thing? Is that a bad thing? If you have a house and you want to renew it, do you want to change a lot of things or do you want to stay and not do anything? Another, you can compare with getting money. If I give you less money, you'll probably buy less food or cheaper foods, or you go for the discounted foods. If I give you more money, you probably buy the more expensive foods, but you still get the same needs. You fulfill the same needs, if that makes any sense. So turnover and requirement, we don't know how that varies. I mean, people can adapt to a higher protein intake diet. People can adapt to a low protein intake diet.

Rhonda Patrick: So you said people in the studies that were used to determine the requirement or being in neutral, at least being in the neutral balance, were these people older, younger? Were they mostly sedentary, physically active? Or is any of that…what's known and what's not known?

Luc van Loon: Those studies in those years, those were most of all healthy people. There's only a few studies that actually had really older people in there, and most of them were relatively healthy and lean. So, yes, there might be differences whether you become more obese, you're more active, you're older or younger, you're male, you're female. Those may all change the requirements. But I think one of the things that we always lose perspective of is what is requirement, what is required for optimal health? And that, of course, depends on what you're used to. I mean, there's no studies that have done it as far as I know. But if you actually have a protein intake lower than 0.8, would you disappear? I don't think so. There's people that actually survive on much lesser protein and so they can regain a certain balance. But also people that over consume protein can regain a balance. So the body adapts. If we weren't able to adapt, we wouldn't be alive today.

Rhonda Patrick: So how is that, that people that are consuming really low protein diets? I personally don't subscribe to that type of diet myself, but there are many people, as you said, that do consume low protein diets, whether it's by choice or not. But you're right, they don't disappear. I mean, when you get to the extreme level, they look like they lost a lot of muscle. But is there some sort of adaptation in other organs that change the way protein is distributed or absorbed?

Luc van Loon: Very, very good question. So when I start talking about something, it's almost in 99.9%, it's about muscle. And also a lot of your viewers will discuss muscle, but of course the body consists of all these different tissues. And if I tell somebody that his arm or his muscle is actually reconditioned completely in two to three months, people are amazed. But then if you start looking at all the other tissues, you'll get even more amazed. And so we started doing that, looking at turnover of other organs. Now, you can't stick a needle in the liver and in the pancreas and in the brain, just like we do in muscle, in order to measure turnover. But we actually do this prior to surgery. So over the last few years, we've actually put tracers, stable isotope labeled amino acid tracers in the body and then measured the turnover rate of all the other tissues prior to surgery. And then during surgery, the tissue comes out. And then we were happy to take some of that tissue to measure the turnover rate. Now translating that more in popular scientific. You have a new liver in the week, you have a new intestine in two days. You have a new brain in three weeks. Brain turnover. Brain protein turnover is about three times as fast as muscle. So all of these tissues are constantly breaking down and building up, breaking up. So every constituent, all the amino acids, are constantly, constantly being changed. I used to tell that muscle is the most important organ and responsible for most of the protein metabolism, simply because you have about 30 kilograms of muscle in your body, but the turnover rates of all your other organs is much higher. So actually, on a whole body level, I think muscle isn't that important for total. So in a total body, we synthesize on a daily basis about 300 grams of protein. And how much do you eat? About 70 grams. So that means that we're recycling 230 grams of amino acids on a daily basis. So realize constantly, one amino acid is being released from a protein in your brain. It gets back into your circulation, it's being actually used to synthesize your right toe. And that is constantly happening everywhere. And so it's amazing that we reuse all these amino acids in the body, and then we renew them, refresh them with only 70 grams. And that's why we need protein. Now, if you refresh with less proteins, probably, as you suggest, turnover rates of some of the other organs might go down. Which ones? We don't know. We know a lot about muscle. We hardly know anything about how the other organs respond to protein intake. So there's a lot to learn.

Rhonda Patrick: Okay, what about people that are engaged in resistance training? So you are putting a stress on your muscle, and obviously that's going to probably increase the turnover as well. So how much do the demands in terms of protein requirements go up? Now, I know it probably depends a lot on what your goals are. You know, are your goals to be an elite body weight, I mean, a bodybuilder, or are your goals to stave off muscle atrophy? But it'd be nice to have, you know, what are some of the requirements for protein intake with people that are engaged in, you know, frequent resistance training, also some aerobic conditioning. Not elite athletes, just regular people that are committed to health. And also, you know, you hear a lot in the bodybuilding community that you should just eat 1 gram of protein per pound, which is 2.2 grams/kg body weight. I'd love to know what your thoughts are on that as well.

Luc van Loon: A lot of questions there. So, the first thing is, protein synthesis is not the same as muscle protein accretion. So the building of muscle is not the same as reconditioning. When people like Stu phillips myself, we measure muscle protein synthesis. Now, the muscle protein synthesis goes up after exercise, when you do endurance-type exercise, but also when you do resistance type exercise. The long-term adaptation, of course, is completely different. Look at the physique of a marathon runner and a bodybuilder. They are hugely different, but they both have very high muscle protein synthesis after a training session. So the protein synthesis is a measure of to what extent does the muscle reconditioned to become more adapted to the type of exercise that you perform. Now, we do see that if you ingest more proteins above 0.8 and towards, say, 1.61 point, even some people suggest 1.8, that you get a more efficient reconditioning. Now, does the muscle need all that protein? No, because, for example, in the endurance athlete, the endurance athlete is not gaining weight, at least I hope not, because that wouldn't be good for him. But he actually is renewing that muscle much faster, and that requires fresh proteins coming in. Now, what I said, the optimal requirements, we don't know, but we do know is that at least for muscle mass gains, so for the resistance type guys that want to gain more muscle, that it tends to have greater gains in muscle mass and in muscle strength if you consume more protein than is what being advised. So if you go towards 1.2 or even 1.4 or 1.6, now going even higher than that, I think it's not relevant, it's not used, it's not necessary. It's also a bit of a self-fulfilling prophecy, because if your body adapts to more protein, it will need more protein. So that is just natural in this situation, your body adapts to its use, so you can actually maintain your body mass on the low protein intake and on a high protein intake. And there must be a sweet spot somewhere. And I think most people are spending too much time thinking about what the sweet spot is because the, 0.8 hardly any – whether we're talking about young or old, there's hardly anybody consuming 0.8. If you're a healthy older or a healthy young sedentary person, you easily consume between one and 1.3 grams of protein per kilo and body mass per day. I mean, if 10 to 15 energy percent of your diet is protein, you easily get to 1.0 to 1.3. And that's also people that don't take supplements or just don't think about the nutrition. If we see elderly of older people in our test, between 1.0 and 1.3. Now, if you're an athlete and you're exercising, you eat more simply because you need to be in energy balance. Ten to 15 energy percent comes from protein. So if you're physically active, you automatically already consume 1.5, 1.6, 1.7 grams of protein. Do the math. Think about Tour de France. Cyclists. They're not big guys. They actually expend about 25 megajoules of energy on a daily basis in the Tour de France. If only 10% of that comes from protein, they already consume well above 2. Not what they need. But people are too worried about the total amount of protein. They're already getting enough protein if they stay in energy balance. It becomes more important when you actually can't eat a lot of food, then it's, then the puzzle becomes more difficult.

Rhonda Patrick: What about people that are not in energy balance. Let's say there are people that are undergoing energy restriction to change body composition, do protein requirements, is it beneficial to change protein requirements and perhaps increase them in that specific condition?

Luc van Loon: What we typically see when people try to lose weight, for example, so if they are on a hypocaloric diet, is that they lose that. If they eat less and they try to maintain their absolute amount of protein, the decline in muscle mass is less. So maintenance of your absolute daily protein intake is more important. And that's exactly what relates what I said before. Your body adapts to a certain amount of protein, and if you suddenly reduce the protein intake, that might go at the expense of muscle. So also when people go into the hospital and they're not exercising, they're eating less, also because of pain and stuff like that, we try to optimize or maintain at least the total amount of protein that they were consuming before they went into the hospital. That will attenuate, or at least attenuate a little bit, the muscle loss that they have. So maintenance of your normal protein intake is an essential thing.

Rhonda Patrick: How does resistance training, and training in general, change the way the muscle responds to amino acids?

Luc van Loon: So exercise increases muscle protein synthesis, also increases muscle protein breakdown, but it increases muscle synthesis to a greater extent than it increases muscle breakdown. So net balance becomes better. That's without food intake. If you throw protein on top of that, then breakdown is inhibited to some extent, and protein synthesis is further increased, allowing you to adapt and to recondition the muscle to what you're aiming for. And that could be like more mitochondrial proteins when you're an endurance athlete, or myofibrillar proteins when you're becoming a more resistance-type athlete.

Rhonda Patrick: Okay, so is that kind of why you were saying when you, let's say, you're training and then you increase your protein intake to 1.6 to 1.8, let's say you're going higher, and you're doing that for a while and your body adapts to that amount, then if you take that away and you're still doing the training, then does it adapt quickly as well? Or will you start to lose muscle mass?

Luc van Loon: We don't know, but I would predict, and let's do the extreme. There's anecdotal reports of people that have a very high protein intake diet. And then you tell them that they don't need that amount of protein. And then they do an experiment and they basically say, okay, you know what, I'm going back to 1.5. And I used to be eating so much supplements, I was sitting at almost 3 grams per kilogram body mass and I bring it back down to 1.5. I'm losing muscle, so I'm not doing it anymore. I'm not sure what would happen if they actually kept it there for a while. Because it's homeostasis, your body adapts. So probably if you're consuming more than 3 grams of protein per kilogram body mass per day, the turnover of other tissue and or the oxidation of the protein will probably be at a higher level. So you can't basically get a new homeostasis within like two or three days. That requires studies that look at changes over time. I mean, like I said, I mean, we now tell everybody that 0.66 or 0.8 is the minimal requirement. I assume that there's people that eat much less protein, but they still stay in balance. If you go to a third world country of people that are not consuming enough food, they adapt. And so it's also on the other side. I think you can adapt to a high protein intake even if you don't need it. Is it a healthy thing? We don't know. Do you increase the turnover rates of other tissues? We don't know. And if the turnover is increased, is that a good thing? Is that a bad thing?

Rhonda Patrick: When you say they adapt, like for example, with respect to the extreme, like, low protein diet level, I mean, they adapt, but you know, they're not building muscle, is that correct?

Luc van Loon: They're not building muscle, but they're maintaining in a balance, in a nitrogen balance.

Rhonda Patrick: Balance until they get older. And then it's harder to stay in the balance if you're not getting enough protein.

Luc van Loon: If they're losing muscle, they're not in balance. But again, then we're talking about muscle. And with the nitrogen balance, you measure on the whole body level.

Rhonda Patrick: Okay.

Luc van Loon: And that's one of the reasons why you can't translate the protein requirements directly to what is happening in the muscle. The muscle just enjoys when it gets more protein. It can do… It's much more modulated. I mean, if you would actually increase your liver or your organs by a higher protein intake, we would probably have a health issue.

Rhonda Patrick: Well, what about you've done some research on anabolic resistance, and maybe you can explain to people what anabolic resistance is and how that is relevant in terms of protein intake for older adults.

Luc van Loon: Yeah. So if you give young, healthy people about 20 grams of a high-quality protein, you see a maximum stimulation of muscle protein synthesis. Giving 40 grams did not result in a greater muscle protein synthesis. We'll talk about the 100 grams later on, probably, but so in the next four to six hours after a meal, 20 grams of protein maximizes muscle protein synthesis. Now, if you do that the same, if you do that in older people and you give them the same 20 grams of protein, they show a lesser stimulation of muscle protein synthesis, and they do not reach that same level, and certainly not the maximum level. So that's what they now call anabolic resistance. We see that the same amount of protein does not lead to the same increase in muscle protein synthesis that you see in young people. That is now defined. I mean, Mike Rennie's group was the first to define that as anabolic resistance. But the question is, what is causing anabolic resistance? Is that because of the age? But of course, if you compare young and older groups, it's not only about age. If you compare a young and an older person, it's the age, it's the lifestyle, it's the habitual food intake. Habitual protein intake. It's the medication, the comorbidities that they have. So you're comparing a lot more. Now, one of the strongest things that increases the sensitivity to food intake is physical activity. Now, if you provide, if you give an older person an exercise session before food intake, their response is almost completely normal. So, much of the responsiveness, the anabolic resistance, can be overcome by physical activity. So, my question is, to what extent is anabolic resistance? Not for the greatest amount, simply secondary to a lower physical activity level.

Rhonda Patrick: Okay, so if I'm understanding correctly, most of the anabolic resistance with older age is attenuated with physical activity, resistance training, just being physically active. Well, that's pretty incredible, because, you know, you're right. A lot of people do, as they get older, they do become less physically active. Certainly people that aren't necessarily focused on their exercise. Right. I mean, normal people that are kind of more active, perhaps when they're in their job and then they retire and then they're not as active. I mean, that's probably the biggest, I think, for the general population. The biggest problem is when they then retire and then they're just sitting at home and then no longer physically active. So knowing that anabolic resistance can be overcome by physical activity is–mostly overcome–is, I think, extremely important for public health. Before we kind of dive into some of that a little bit more, I wanted to, you mentioned something about being overweight and obese with respect to protein requirements, because in the United States there, many people are overweight and obese. And people like listening to this podcast might look at that number, 0.8 grams per kilogram body weight and directly translate that to their weight, which could be quite high. So how does a person who is overweight and obese, perhaps it's not as important because they're probably, like you said, they're consuming enough food so they don't have to worry about it. But there are anal people that want to think about calculations no matter what. How does that person approach how much protein they should be taking in when they are obese or overweight?

Luc van Loon: If you would actually modulate your protein requirements towards the tissues that require the protein, then it would be better to basically base it on fat-free mass. Because of course, a lot of the fat mass is not that metabolically active. Most of it is fat depot. So turnover of protein is relatively small compared to the organs in the muscle. So if you have the fat-free mass, all the organ mass and the muscle, and actually say like, hey, 0.8 for an 80-year-old or 80-kilogram weighing man, then also related to the 0.8 based on those 80, not on the 20 or 40 excess fat depots that you have on you.

Rhonda Patrick: So people, most people aren't going and measuring their fat-free mass, but that is something that can be done. People can go get a, would you say doing a DEXA scan would be something that would be more?

Luc van Loon: I mean, there's so many options. I mean, you can make a body volume scan, you can, there's nice apps nowadays, we heard it yesterday in the conference also. But you can also do a DEXA scan or body circumference measurements or... But most people know how much overweight they are. Come on. I mean, if you're 180, you know that somewhere between 80 and for meal, you should be somewhere between 80 and 90 kilograms. If you're 110, it's probably you have about 20, 20 kilograms excess. And now taking myself as an example, you know how much overweight you are, and most people do know that.

Rhonda Patrick: Yeah. With respect to the resistance training, sort of how it's tied to protein intake and increases in muscle mass and even strength would be something I'm interested in because there have been some meta-analyses. Stu Phillips did a really nice one where they looked at protein increasing protein intake and increases in, they said, lean body mass and then also strength. And it was, what kind of was striking to me and stood out to me was that with increasing amounts of protein. So when you start to get up to like for younger people, 1.6 grams per kilogram body weight was associated with a modest increase in muscle mass, but it was very minor increase in strength. And these were people that were doing resistance training. And the same went for elderly. They started to actually have increases in muscle mass at a little bit lower. They were 1.2 grams per kilogram body weight. And it was the same thing, modest increases in muscle mass and minor increases in strength. And that's where I felt like, I thought muscle mass strength was easier to gain with resistance training than muscle mass. So I'm wondering, is this something to do with measuring lean body mass? Or maybe just the resistance training program wasn't robust enough to improve strength.

Luc van Loon: I mean, so I think that the nutritional benefits of gaining muscle mass and strength depends on the availability of protein and the gaining of muscle mass, of course. And then also the capacity to do that training, because they also interact, of course. But if you go back like, hey, the fat free mass could also be a little bit organ mass, of course. And so maybe some of that gain in fat-free mass is actually in the organs and not necessarily the muscle. That's also possible. But muscle mass and muscle strength are not that tightly regulated or not coupled as you think. I mean, you know that yourself. If you go to the gym and you have never been there the first four, five weeks, you see that your strength goes up tremendously. I mean, you take that pin and you put it on 20 kilograms and a week later you put it on 34 weeks later you put it on 40 and think, this is awesome. And then you know, how much strength am I gaining? And then you're looking in the mirror and you're thinking like, hmm, hmm, nothing much has been changing, I still look the same. And then you don't get back to the gym anymore. You just quit. Ninety percent of the people listening, including myself, that happens. So the gain in strength is the first step. The body tries to generate more strength with the stuff that it has, and most of that is neuromuscular. And then when the body constantly is being driven to do more than it wants, then it starts thinking like, okay, now it maybe becomes more efficient to build some extra muscle. I mean, it would be strange if the muscle starts building extra muscle simply because you overexerted yourself once. It's a very energy costly process to build more muscle. So it takes a while. So first you gain strength, and then you actually follow up with more muscle. So there's also a time relationship between the two. Also the other way around. I mean, when we become older, we lose more strength than can be explained by the amount of muscle that we have lost. So there's also a neuromuscular component. And of course, if you then start training these people the first few weeks, even months, you don't see that much, but their strength goes way up. So those two things are not one on one. It's not a proportional linear relationship.

Rhonda Patrick: Can you give a little bit of a range in terms of maybe not exact? Cause you might probably don't know, but with respect to that time course. So when you start to do resistance training and your strength is going up, like you said, how much longer of a lag before you start to perhaps visually see, or even if you're measuring it, can see increases in actual muscle mass?

Luc van Loon: Yeah, that depends on the type of training, where you're coming from, what your body mass is. I mean, you can hide a six-pack pretty well if you have a lot of excess fat, of course. So that really depends on the type of program that you do and the body morph that you have.

Rhonda Patrick: Okay, maybe we can get into that a little bit more in a minute. I wanted to kind of continue on the nutrition part with protein distributions. You've done a lot of research in this area as well. And, you know, I had done some, some reading, preparing for this podcast on, like, some of the nutritional surveys that are done in the United States–they're called NHANES–in terms of, like, how are people typically distributing their protein amongst their meals? And I think probably it's very similar to what's found in Europe, where people are eating... The majority of their protein is skewed towards their evening meal, their last meal of the day, and in most cases, at least with respect to this NHANES data, it's about three times the amount of protein in their evening meal versus their morning meal or even their afternoon meal. Does it matter with respect to how the muscle responds to amino acids throughout the day? Is it better to evenly have your protein evenly distributed, or can you skew it in the evening and still have the same, I don't want to just say increases in muscle protein synthesis, because, as you mentioned, that doesn't always translate to gains in muscle mass. People are more interested in gains in muscle mass. So let's leave it with that endpoint.

Luc van Loon: So we try to make it more simple, but it is actually much more complex. But if you consider that a single meal containing 20 grams of a high-quality protein maximizes muscle protein synthesis for up to four to six hours, then it makes the most sense that every main meal throughout the day is an anabolic stimulus so that you would have 20 to 25 grams of protein in your breakfast, 20 to 25 grams of protein in your lunch, and 20 to 25 grams of protein in your dinner. And then, theoretically, you have three anabolic stimuli throughout the day helping you to optimize muscle building, muscle reconditioning. I actually make that mistake all the time by saying that it's not about muscle building, it's optimizing muscle conditioning. And that could be for the endurance athlete, that would be better muscle to do endurance type exercise, and for the bodybuilder, that might be a bigger muscle. That's what now everybody's being advised. For athletes that consume more than those 75 grams of protein, that you can also add another meal moment. And that's, for example, the pre-sleep evening snack. For example, if you exercise in the evening, you take a protein rich snack after that exercise session in the evening. And when you had dinner, for example, at 4 or 5 or 6, and you have a training session between seven and nine, you have a protein-rich snack, a snack at 9 before you go to bed at say, 11. And so that's what a lot of athletes do, just have a nice distribution throughout the day. The long-term studies, long term, semi long term, on nitrogen balance or on muscle protein synthesis are not that clear. There are some studies saying you have better retention of your protein and of your nitrogen when you actually have a nice distribution. But we've also had a recent study that we showed that if you have a huge meal, you have a greater anabolic response when you assess it over a more prolonged period of time. Now, a lot of people are now asking us like, should I have one meal? No. It's a study to show that the six-hour or the four-hour response to a single meal can be longer if you give more protein because all the protein still needs to be digested and absorbed. But that doesn't change what I think now from all the evidence that we have, it's being advised to have a nice, even distribution of your protein in your main meals.

Rhonda Patrick: So let's talk a little bit about that study, since you brought it up, because it was surprising to many people. So maybe you can talk a little bit about the difference in terms of the quantity. It was like 100 grams of protein versus what has previously been shown, maybe 30, I think, grams of protein was something that's been shown in terms of maximizing. Now, this was muscle protein synthesis that you were looking at.

Luc van Loon: So the older studies, there's basically two dose-response studies that show in healthy young people at rest or after exercise 20 grams maximizes muscle protein synthesis for somewhere between four to six hours after the meal. So in that time period, four to six hour postprandial period, we call that. Some of that protein might not have been digested and absorbed if you give more than those 20 grams. So the 40 grams that they showed in those studies didn't show a greater response, but they only measured for four or 6 hours were depending. Now, we wanted to do a study to show that if you give 100 grams, which is absolutely not something that I'm suggesting that people should be consuming, that it takes longer to digest everything, and that you have a longer stimulation of muscle protein synthesis over a more prolonged period of time. So we also measured not over six hours, but over 12 and even 24 hours. And then we see that you get a greater response. Now, the interesting part of this study is we also assessed digestion and absorption. Now, that is difficult because how do you do this? Now, instead of infusing tracers only and measuring the incorporation in muscle, that's how you measure muscle protein synthesis, we actually did an experiment before that. We infused a cow with labeled amino acids. So you have amino acids with a chemical flag stable isotope labeled. We infuse it in the cow. The cow actually incorporates it in the milk. So we have milk protein and we extract the milk. We extract the milk protein. So we have milk protein, where those labeled amino acids are incorporated, and then we provide that protein. So we can see the digestion, we see those labeled amino acids coming out of the protein being released to the circulation. Then we take a blood sample, we can actually see those amino acids. So we see how much of the protein that you ingest is released in the circulation. And then we can even see how much is converted to muscle. And then you see that it takes much longer to get all those amino acids in the circulation and also to get a longer stimulation of muscle protein synthesis. So simply, regard also the fact that time is a factor in all of this. But of course, most of us eat one meal and then four to six hours later, the second meal. And that's why all the previous studies always looked at four to six hour postprandial periods.

Rhonda Patrick: Unless it's your last meal of the evening. So the question then is if it's your last meal in the evening. And, you know, let's say you've already distributed your protein intake fairly decently in your first two meals, some people will talk about a minute time-restricted eating and caloric restriction. And let's say you want to go a little higher for your, maybe not all the way to 100 grams, but 60, whatever. Then if you speculate on this, there's two parts to this question. Would you think that the increase in muscle protein synthesis would be higher if you had ingested 60 grams of protein in that last meal versus 25 throughout the evening? Like we're talking like [inaudible] hours? And also, what if you then wake up in the morning and then you have again your first meal? Is that going to change the muscle protein synthesis or are you better off having that meal higher? Are you going to get just, are you really maximizing it?

Luc van Loon: I love those questions because the three questions that you now ask is probably seven years of my life. So one of the things how I should start answering this is that we see a lot of people in the hospital losing muscle, and so they're admitted to hospital losing a lot of muscle. And we know that the loss of muscle or muscle mass is an important predictor of clinical complications, readmission, health, etcetera. So we wanted to do something for patients to reduce muscle loss. So we thought, like, if we give these just in line with athletes, if we give these elderly people another meal in the evening, can we minimize muscle loss or stimulate muscle protein synthesis? Now, when you're in the hospital, probably hear the same thing. You get your last meal about 5:00 or 6:00 in the evening, and then the next meal is breakfast the next day at 9:00 so you spend more than 15, 16, 17 hours in an overnight fasted state, which is maybe nice for people trying to lose weight or anything like that. But for people at risk of muscle loss, it's not a good thing. So we started thinking about, if you give protein in the evening, is it digested while you sleep? Does this all work while you sleep? Now, that's difficult because you can't take muscle biopsies when somebody sleeps and not wake the person up. And you also can't ingest protein while you're sleeping. So what we did is, and that's when we started doing studies with the older people, the great volunteers, much better than most of the athletes. They call us. And then they actually say, look, I was in your lab last year. Can I come back? Do you have a new study running? And then I would say something like, oh, yeah, you can come over. What we'll do, we'll put a nasogastric tube down your nose, in your gut, we take a muscle biopsy, then we put you to bed in the hospital. Then at 2:00 at night, while you're sleeping, we'll tiptoe next to your bed, put 40 grams of protein in your gut, and then wake you up in the morning at 7:00 with a muscle biopsy. And then they respond like, where can I sign up and when can I come over? So these are cool studies, but they showed that if you give 40 grams of protein in the evening, that protein is digested and absorbed while you sleep because we use that intrinsically labeled protein so we could follow it, and it's actually converted to muscle. Now, that study was weird because when we published that, that was a nice proof of principle study. I got a lot of coaches and people calling me, asking me where they could buy those nasogastric tubes. And I said, no, this is a proof of principle study. Just have a protein-rich snack in the evening. Just to make that clear. We actually followed that up with an athlete study where we showed that having a protein-rich snack in the evening is digested and absorbed and stimulates muscle protein synthesis overnight. And so that amount of protein will help you reconditioning more efficiently. That's the first answer the question to your first question. Now, the second was, is it of benefit on top of knowing that you'll have breakfast and lunch the next day? So we also did that study. We provided protein in the evening or we didn't provide protein in the evening and looked at the response to breakfast. Now, response to breakfast in both conditions was exactly the same, to my surprise, because I expected if you gave a lot of protein the evening before, then the response to breakfast would be minimized. But it wasn't. It was exactly the same. So it does give me some insight that at least in the first 24 hours, you have a greater benefit when you provide sufficient protein to maximize the reconditioning.

Rhonda Patrick: What about people? So time restricted eating? You mentioned a lot of people do practice time-restricted eating and they're eating in an eight-hour window and they're fasting for 16 hours. And you've done some research in this area as well. So can, you know, eating that large evening, that large protein bolus with your last meal, what if it's earlier and it's not like right before sleep because you have your feeding window, your eating window, and then you have your fasting window. Do you think, based on your study, with 100 grams of protein, really extreme case, that that protein will be digested longer and incorporated into muscle for muscle protein synthesis?

Luc van Loon: So based on the theory that you need an anabolic stimulus every main meal in order to get the optimal 24-hour response, then you would actually have to conclude that intermittent fasting of time-restricted feeding is not a good thing. But we've done a study, a more longer-term study, Imre Kouw did that with labeled water and she did that in Melbourne, where I had a visiting professorship position there. And we didn't see a difference in muscle protein synthesis with the time-restricted eating versus the non-time-restricted eating. So it's possible the explanation is that if you have a period where there's less or there's no food intake, but you had a greater meal as the last one, that actually also had a greater response over a more prolonged period of time, just like the 100-gram study. So it's possibly that that evens it out. The other big question is, of course, why would you do time-restricted eating or intermittent fasting? The other thing on that study was we didn't see differences. Or that project, I should say, is we didn't see a difference in fat loss. And I have a lot of people calling me and saying like, but the time-restricted eating, intermittent fasting really works for me. Now, I did it myself as well, and it works really well. Why? Because in the morning I go to work, I don't think about food because I'm too busy and everybody's just walking into my office. By around 4:00 I get a little bit peckish. So I start eating something. And then I get home around 6:00. And around 7:00 I open up the computer to see what crap emails I got. And then I start having my main meal and snacking. If I decide to not eat after 6:00, I will eat much less than I actually require, so I'll lose weight. So basically, because more than 70% of my energy intake is after 7:00 at night, time-restricted eating would be great for me. But if I would eat all the food that I would eat after 7:00 throughout the day, I would not lose that fat mass and I would not lose weight. So it's a good way for people to cope with a lower energy intake.

Rhonda Patrick: Right, I think there's now been many, many studies that have done that have found that people naturally doing time-restricted eating, you know, when they're free-living conditions, on average, reduce their calorie intake by about 200 calories per day. And that's just, you know, natural because people don't snack or they don't eat that dessert or they skip, you know, because they are trying to restrict their, their meals into a shorter time period. But, and I think you've even shown this and other studies many studies have shown, while if you do keep calories the same, you will not lose fat free mass and weight. Right. Then glucose, the glucose homeostasis is still improved by not eating in a huge, you know, like, by restricting your time eating window shorter to, let's say, 8 hours, you know, in some cases 10, but mostly eight, even shorter than that, six hours. So there are, there are people also that are very interested in their glucose homeostasis that, you know, want to eat within a shorter time window as well. But the question then goes is, well, if they're skipping meals or skipping snacks, then they're potentially skipping protein intake, right? And so if someone is doing the time-restricted eating schedule where they're eating within an eight-hour window, then they really do need to make sure they're not losing their protein, correct?

Luc van Loon: Yes. And so if they maintain their normal protein intake, then they should be fine, because it's possible that more protein per meal has a greater effect, like the 100 grams. But the other part is also, I mean, let's not. I mean, it's funny, but we always end up talking about nutrition and then we don't talk about the physical activity because, I mean, the same thing when people ask me, like, what should I eat to lose weight? And I always say less because there is no magic bullet. But the physical activity, we know from all hypocaloric diets that if you actually are on a hypocaloric diet, that two sessions of resistance exercise throughout the week prevents the lean mass loss. So maybe instead of focusing on the protein, focus on physical activity in order to maintain your fat-free mass by doing two resistance exercise sessions a week, much more important than the protein.

Rhonda Patrick: So let me rephrase my question. For someone who is doing time-restricted eating in an eight-hour window, fasting for 16 hours, and they are engaged in resistance training at least three times a week, minimum. And they're taking in their protein, they're not missing their protein, and they're doing the resistance, right? Yes. Can they gain muscle mass? Can they gain it?

Luc van Loon: Yes.

Rhonda Patrick: Okay.

Luc van Loon: That's an absolute yes. I mean, there's even studies that. So again, 0.8 grams of protein, you can actually gain muscle on 0.8 grams of protein. Maybe you can gain more muscle on 1.2, but you can still gain muscle on the 0.8 grams protein per kilogram body mass per day. The body is much smarter than we think. If you actually do exercise and we ingest the same protein that we can track throughout the body, we see that the same amount of protein is of course digested and absorbed. But more goes to the leg that it exercises. So there's also an efficiency effect. Physical activity makes you more of what you just ate. So more of the protein is actually converted when you perform physical activity. So the body gets smarter how it handles protein.

Rhonda Patrick: I have a question. So if–we were talking about protein distribution and perhaps, you know, it being beneficial to more evenly distribute protein–but how does physical activity, because you said physical activity sensitizes, I mean, you said it sensitizes muscle to amino acids. How does that, does that change whether, I mean, you would think that in the background of someone who's physically active, does all these other little differences matter?

Luc van Loon: I think so. I mean, all those little things that matter. I mean, to look at a cyclist, it's the bike, it's the helmet, it's the nutrition, it's the training, it's the mental coaching. And all of this together make the better athletes. So it's all these small things. So what is interesting to see is that you have an anabolic response to feeding, you have an anabolic response to exercise. You have an anabolic response, a greater anabolic response when you compare the two. Now the nice thing is that I think question number one, the question I was being asked the most is do I need to take the protein before or after the exercise session? Which is almost the same question you're asking, should I do the exercise before the meal or after the meal? It's basically also the same thing. It doesn't really matter that much because exercise makes the muscle more sensitive to the stimulation of muscle protein synthesis through food intake. But it does so for up to 24 to even 48 hours. So if you do an exercise session today, your response to breakfast tomorrow morning will be greater, but also lunch tomorrow afternoon and also dinner tomorrow night. And so after that you have your second exercise session. So it's not about what should go first, but it's a consistency of training and meals in between. And the training will make your meals more efficient in how they optimize muscle reconditioning.

Rhonda Patrick: Well, the thing that's so interesting about this recent study that you published on the higher dose of protein and that being incorporated into muscle is so if you have that 24 hours anabolic window, as you're saying, and you're going to be more sensitive to amino acids throughout that 24 hours, of course, in every meal. So if you have ten meals on the extreme end, okay, every ten times the protein, you're going to be sensitive to that protein because it's still within that 24 hours window. However, if you don't have time because you're working, as you said, to eat three or four or five meals throughout the day, it's also nice to know that you can go a little further than 30 grams in those, let's say, three meals and perhaps still get a similar amount of muscle protein synthesis. In fact, let me ask you to speculate. Let's say a person with, did two people or the same person, and you did a crossover study where they do both conditions. They're doing their resistance training. Their anabolic window is 24 hours. They're sensitive to the amino acids. The first time they're eating, you know, let's say, what, 80 grams of protein. They're doing that within five meals or they're going to do it within three, do you think they'll have the same amount of gains in muscle mass?

Luc van Loon: This is, I mean, this is cool study, but I think if there's differences, they will be too small to pick up. That's one. If you would have, each of those meals would have 20 grams. So it's depending on total protein intake. If you do, for example, five times 20 or two times 50, does that make sense? I don't think you'll find any difference there. If you would do, I would be more, less sure about my case if you would do 20 times 5 grams versus three times 33.3.

Rhonda Patrick: Okay.

Luc van Loon: That maybe, maybe there's a difference that you don't reach that so so called losing threshold. But to be honest, if there's, the day before there's physical activity, a good training session with the legs involved, I'm not so sure whether we would be able to pick up a difference there.

Rhonda Patrick: Okay, so it is…

Luc van Loon: Pure theory, of course.

Rhonda Patrick: Yeah. Speculation, essentially. It sounds like certainly in the context of training in the background, that you can skew your protein somewhat with your meals and still not be missing out on what you otherwise would gain in muscle mass.

Luc van Loon: Rather not worry about that. But don't miss that training session.

Rhonda Patrick: Absolutely. That's the essential thing. That's the baseline.

Luc van Loon: But the more people talk about nutrition, the less they're actually doing the training. That's what you often see.

Rhonda Patrick: I know, it's true. It's absolutely true. And I do. We're gonna. I'd like to continue on the nutrition because you've done so much research in this area, but I wanna get to the training. But we've been talking about protein, like this general thing, like protein. And so there's food sources of protein, there's supplemental sources of protein. There's plant sources of protein, meat sources of protein. So I was kind of wanting to start maybe with just let's talk about animal sources because most people are eating meat and fish and poultry. Luc van Loon: Dairy.

Rhonda Patrick: And dairy, yes. Like how in terms of skeletal muscle protein synthesis, in terms of gaining muscle mass, if you're having the same amount of protein on a gram basis from food versus a protein shake, and it probably will depend on the type of protein shake, but is there going to be differences in gains in muscle mass?

Luc van Loon: Not measurable, but of course. I mean, if you assess muscle protein synthesis, if you get whole foods in from an animal based, you might get a little bit more sluggish response, saying the increase in circulating essential amino acids and leucine in particular, will be less rapid than when you actually ingest, say, 300 mils of a protein shake with the protein isolate or the protein concentrate. But we will never be able to actually pick up those differences because they will be very, very, very minimal. But now we're talking about meat that is cooked, eggs that are cooked, because then we see that actually digestion and absorption is very rapid. And we see almost the same increase in essential amino acids and leucine than when you get the isolatory concentrate.

Rhonda Patrick: Okay, so of course there's differences because if you're eating food, you're getting, you know, vitamins and minerals and fatty acids and all the other, you know, important micronutrients and macronutrients that are required for…

Luc van Loon: And if you have these, these products are coming in a combined meal because that's typically something that has much less research being done. We're starting to do that now, but it's often complicated because then you have all these different products coming together. You have anti nutritional factors. I don't like the term anti nutritional factors, but that's what they call them. But you have fibers, you have more energy, so your gastric emptying is reduced. So everything gets more sluggish and then it gets more difficult to compare stuff. So it always depends whether you have your, your protein isolate or concentrate, whether you have your whole food product or you have that whole food product in a meal. That will change the dynamics of digestion and absorption and therefore also direct impact on muscle protein synthesis.

Rhonda Patrick: But when you say sluggish, I mean, do you just mean delayed? Essentially, those amino acids will get to the muscle, but it'll take longer.

Luc van Loon: Correct.

Rhonda Patrick: Okay, well, in that sense, I mean, we're talking, in the absolute sense, gains in muscle mass, then it doesn't really make a difference if you're doing the animal source. We're talking about animal source right now.

Luc van Loon: Yes, yes. Because, I mean, if it's sufficient, if it's 20 grams, you'll get above a certain threshold and you'll definitely have the full anabolic signaling that you expect in muscle.

Rhonda Patrick: But of course, people are also interested in not getting, if they're doing caloric restriction and basically trying to change their body composition, protein shakes can help with that if they're lower in calories, lower in fat, and then you're getting your protein without the other fat sources.

Luc van Loon: So I always advise people to get most of the nutrients from their diet and not from supplements, as I discussed this morning. But what is interesting, sometimes sports nutrition or supplements can be used to make it more practically feasible to do it. And I always use for students and I use, the example is, for example, a sports drink. A sports drink gets you the carbohydrates during exercise. You can also do that with a plate of spaghetti, but it's not that easy to cycle on a bike when you have a plate spaghetti in front of your nose. So it's an easier way to get the nutrients you need in a setting that is sports-specific. Now, if you're in a gym and you want to take a certain amount of protein and you don't want to make a short meal and you want to restrict calories. Yeah. Then sometimes a protein shake is easy, easier.

Rhonda Patrick: Is there a difference with respect to the source of protein supplements? So, for example, if it's sourced from casein versus whey versus egg white protein, with respect to, we're talking about skeletal muscle protein synthesis and presumably increases the muscle mass.

Luc van Loon: Yeah. So this is stuff that we, the whole intrinsically labeled cow. So the cow infusion, getting intrinsically labeled milk, and we extracted whey and casein in order to show the digestion and absorption kinetics and also the capacity to stimulate muscle protein synthesis. Now, we've done these studies years ago, and that shows that micellar casein is a slowly digestible protein. So the increase in circulating essential amino acids in the blood is more sluggish than when you ingest whey protein, which is a more rapidly digestible protein. And so the whey protein gets or is more rapidly digested, greater increases in muscle protein synthesis, and also has a greater anabolic response, greater increase in muscle protein synthesis. Now, we thought that maybe only because of the more rapid digestion and absorption, so we hydrolyzed the casein, to make it more rapidly digestible. So it was just as easily digested and absorbed as the whey, but it still had a lesser response. So that might be due to the lesser amount of leucine in casein than in whey. Whey has a higher leucine content and we know that leucine is an amino acid that has very strong signaling properties. So it stimulates the mTOR pathway and therefore it sets off the whole anabolic cascade. And we also double-checked that by adding free leucine on the casein and we got a greater response. So in short, we know that the anabolic potential of a protein is related to the rate of digestion and absorption, and the amount of at least the amount of leucine in combination with other amino acids. And that's the whole basis of why whey is more popular with athletes than casein. But the differences are very small. And so for practice in combination with diets and throughout the whole day, all the food that you eat, it's very minimal. But of course, I mean I ride a bike that is only nine kilos, but I might have actually 15 kilograms of overweight. So I could actually do with a much heavier bike. But I still want the fastest bike and the lightest bike. And so people want the best supplement. Does it make that much of a difference? I don't think so that much. Sitting upright while you eat or actually chewing well, has also a huge effect on the rate of digestion and absorption. But these differences exist. But the differences are very small, if you compare milk, whey, or egg protein.

Rhonda Patrick: Oh, egg white as well.

Luc van Loon: Egg is also great from amino acids composition and also digestion and absorption. It's great.

Rhonda Patrick: So you're talking about in the real world here, you think maybe to most people those differences aren't so important. To some they are like the ones that are really optimizing every just little thing. But what about in the context of research and data, that's not… like you compare studies and someone's using casein and then you got whey and then their time when they do it. Maybe the casein hadn't been absorbed. Conflicting data, I mean methodological differences, seems like it might.

Luc van Loon: So all of these things. So we're scientists, we're trying to figure out what are all the aspects that define digestion and absorption and the capacity to stimulate muscle protein synthesis, what we call postprandial protein handling. And so we want to know which factors play a role. But all, of course in a normal situation you have all these factors together. You have protein quality. In what matrix that protein is being ingested from? A food or a meal. How that protein is processed, how you eat it, and even the body position in which you eat. And so these are all these different things. And now, one of the studies that we've done, for example, is eat eggs or eat the eggs in a boiled form or in a raw form. Now, this is also a little bit of a joke. Not a joke, but everybody knows the Rocky movies, and, of course, there's some guys in our lab that love these movies. And I was actually growing up with those movies. So you see Rocky getting up at 5:00 in the morning, and he gulping down, like, five raw eggs, and then he does his training session. Now, I thought it would be fun to actually see whether, instead of having a Nature paper, whether we could have a paper with Sly Stallone as a co-author. So, basically, what we did, we did a study to see what the digestion and absorption and muscle protein synthesis is after ingesting raw eggs versus cooked eggs. Now, what is really nice to see, you have exactly the same protein, but cooking actually denatures the protein and results in much more rapid release of these amino acids in the circulation. And theoretically, that should also lead to a greater muscle protein synthesis. But we provided sufficient eggs, so probably the total amount of protein was sufficient to maximize the response. So, on muscle protein synthesis, it was exactly the same. So, of course, I sent it off to Sylvester Stallone's home address, but never got a response, unfortunately. So we couldn't make him a co-author. But the title is still, Was Rocky Right or Wrong? Should you boil your eggs? And, yes, boiling is one of the issues. Same thing as consuming how you consume your food. We did studies sitting upright or lying down, which is, of course, very relevant for people in the hospital, because a lot of people are being fed lying down. But sitting upright actually stimulates gastric emptying. So the protein actually gets faster in your digestive system. You get a faster release in circulating amino acids and, therefore a greater stimulation of muscle protein synthesis. Chewing, same thing. We infuse the cow with labeled amino acids. For a Dutch person, it's hard to accept that only 25% of your expensive tracer goes into the milk. So we butchered the cow. So suddenly we had intrinsically labeled meat. We provided subjects with that meat, provided as minced meat or as a steak. Huge difference in the rate of digestion and absorption. So also, chewing and cutting up your food is an important factor.

Rhonda Patrick: Now, are these important? So when you're saying that it's a greater stimulation in skeletal muscle protein synthesis at the time you measured, but will they normalize eventually over time, so that it's less of a difference in the real world, more of a difference in the lab in terms of when you're studying.

Luc van Loon: I think in the long run, it increases the efficiency by which the protein is being used for muscle and tissue protein synthesis. But of course, it becomes less relevant when you consume enough protein. It becomes more relevant when your total food intake is very low. So, for example, people that do not resistance exercise because they're lying in bed and they are hurting, and they are actually anabolically resistant because they also have inflammation and sepsis, and they can't eat food and they can't chew and they can't sit upright, then all these factors come together, and then you have a very dangerous situation. And then having all these little specks will greatly improve probably their health. For the healthy person that already consumes a huge load of protein, then those difference quality doesn't become. So I always like to put it this way. You can compensate for quality by greater quantity. And that's what every athlete already does, because he or she needs to consume more food, because he's more active, has a higher energy expenditure, becomes more important on the other scale.

Rhonda Patrick: It's good to differentiate that. I want to kind of shift back and talk about the protein source, because we've talked about the animal source, we've talked about supplemental sources of protein from animal products. But there's also a large percentage of people that are vegetarian and vegan who don't consume any animal products. So maybe you can tell people a little bit about the differences between food sources, plant sources of protein versus animal sources of protein.

Luc van Loon: So first, and then again, I have to make the difference between whole foods, protein isolates and protein concentrates. So if you want to consume protein through plant based foods. So beans, lettuce, nuts, whatever, it's more difficult to get a certain amount of protein in. If you want to ingest 20 grams of protein through eating meat, 70 grams of meat. If you want to get 20 grams of protein in by eating potatoes, you have to eat more than a kilogram of potatoes. So first of all, it's just more difficult to get the same amount of protein in if you actually consume it as whole foods. And then when you consume it at whole foods, most plant based foods have anti nutritional factors. So the capacity for you to extract that protein through your body is less, so the digestibility is lower. Those are the two issues when you have plant based foods. Nowadays, and much of the research has looked at the proteins that are actually in plant based foods, extracted those proteins and then assessed their capacity to stimulate muscle protein synthesis. Has been done for some proteins like wheat protein, soy protein, a lot, pea protein, about five different proteins that we and others have actually assessed, and then some of them. Actually, some of these studies show a lesser capacity to stimulate muscle protein synthesis when compared to an equivalent amount of mostly dairy protein. That might be attributed to the fact that there's less leucine, less essential amino acids. And sometimes most of the plant-based proteins are deficient in one or more specific amino acids. That's often methionine and lysine. The last five years we have been trying the protein extracts from pea and gluten and corn. And actually if we give, in healthy subjects, we give 30 grams, which is quite a lot of protein, we don't see a difference with dairy protein. So if you give sufficient of the protein of the protein extract, where digestibility is high, there's not much that much difference in muscle protein synthesis. However, if you would take it from a plant-based food, then on a certain equivalent amount of protein, less of that protein becomes available. And that is, of course, then you have to compensate for that a little bit.

Rhonda Patrick: So vegans that are interested in gaining muscle mass, obviously preserving muscle mass, but also gaining muscle mass with their resistance training programs, they can supplement with plant-based protein powder sources that will allow them to, on a gram-per-gram basis, especially if it's a high enough dose, gain the same muscle mass as someone doing, let's say animal-based protein supplements. Potentially.

Luc van Loon: I think so. They don't necessarily have to supplement. Supplements is probably easier. They can also compensate for lesser quality by greater quantity. But then you have to consume a huge amount of food and of course, you improve the quality of your protein sources by having a very diverse palate of plant-based foods. So if you really know what you're doing from a nutrition perspective, dietetics perspective, then I think you're quite capable doing that on a vegan diet, but it's more difficult. And, of course, if you start using plant-based protein isolates or plant-derived proteins, I should say, it gets easier.

Rhonda Patrick: And what about, so you mentioned pea protein is what you looked at in your study and compared to dairy, when 30 grams and 30 grams there was no difference in terms of skeletal muscle protein synthesis. What about so is pea protein different from rice protein in terms of its amino acid composition? Is there a protein powder that's better, perhaps for vegans that are interested in increasing their muscle mass?

Luc van Loon: So we basically, years ago, we looked at all the commercially available protein extracts. So plant-derived proteins, and then you see that some of them are actually low in leucine, but some, just as corn, is actually higher in leucine than most animal-derived proteins. So not all plant-based proteins are the same. The deficiencies in lysine and methionine is also... One protein can be very deficient in methionine. The other one is actually deficient in lysine but not in methionine. So there's not one specific protein that I would say that one is the best. But you can mix up and blend different plant-based proteins that actually together have a very nice protein-balanced amino acid profile. So combinations are great. What we expected from our studies with the individual proteins, that they would actually show a lesser response, and that by adding some milk protein, we would actually compensate for that. But in all those proteins, like the pea protein, we actually did not find a lesser muscle protein synthetic response. But I do need to note that we did that with 30 grams of a protein extract. So you don't have the digestibility issue.

Rhonda Patrick: What would be. So you mentioned lysine and methionine. Maybe you can explain to people why those are also important. You mentioned leucine and how that stimulates mTOR, and that's important for muscle protein synthesis. But why is lysine and methionine important? And then maybe also why would, what would be a good combination of plant-sourced protein powders? Perhaps to get all those, like you said, pea protein? Is there something else in combination with pea that would cover all the bases?

Luc van Loon: Yeah. So one of the things, I mean, some amino acids may have stronger signaling properties, but of course, if you're trying to build a protein, you need all the building blocks, all the different building blocks. And that includes methionine and lysine, of course. So you need sufficient of all the amino acids. Now you can actually take blends with... And we used a blend with three different plant-based proteins, and that worked fine. But you also see that some combinations, for example, one's low in methionine and the other one low in lysine, they actually make nice blends. And funny enough, if you start looking at those proteins, then you suddenly realize that all over the world, people are consuming meals that actually have proteins that are very nicely compository or matching. And so when I saw those data the first time, I suddenly realized why a fajita actually has beans in it. So the wheat and the beans is actually a nice complement called complementary amino acid, amino acid mix. So it's really funny if you see that somewhere people have actually noticed that.

Rhonda Patrick: And then sprouting, I think also some of the, you can get sprouted quinoa, source of protein, where it's getting away…. Some of the, as you mentioned, like some of these anti nutritional components like the fiber matrix that are in some cases other lectins and they're sort of inhibiting some of the absorption of protein. What about protein isolate versus concentrate? Which one is, is it better to consume protein isolate for higher protein?

Luc van Loon: I would prefer the product where the protein actually is in. So not even the isolate or the concentrate. But then if you're using a supplement and you want to take the pure protein, then you can take the isolate to the concentrate. The isolate is only the protein. The concentrate is basically the concentrated protein. So it still has other stuff like for milk protein concentrate. It still has lactose in, it still has some other stuff, some fat in there. So. Yeah. Is one better than the other? No, it depends on what you're aiming for, what your nutrient targets are, basically.

Rhonda Patrick: Yeah. If someone's interested in lower fat content and more protein content.

Luc van Loon: Yeah. Then you would go for an isolate.

Rhonda Patrick: Of course, protein isolate. Okay, so we've talked about leucine and how it's very important for activating mTOR. Can you talk a little bit about the leucine threshold and how resistance training, physical activity, changes that leucine threshold?

Luc van Loon: Yeah. So if you ingest 20 grams of protein, you see a strong, robust increase in muscle protein synthesis that peaks around three hours after a meal and then it wears off in about five, six hours. Now one of the factors in that response is leucine. The postprandial increase in circulating leucine sets off an anabolic pathway in the muscle and is responsible for that stimulation of muscle protein synthesis. Twenty grams for whey protein, that will be about 2 grams of, 2 to 3 grams of leucine. So you can also give that as free leucine or as the branch chain amino acids. And we've done that as well. We also see that very strong increase in muscle protein since first two hours, but then it wears off much more rapid. So you need the leucine to stimulate the process. But then you also need a sufficient supply of all the amino acids to allow muscle protein synthesis to continue for a while. So it's a double whammy. It's both the signaling and supplying enough of the building blocks. And that's the leucine threshold. Now exercise reduce…makes that like we said before, exercise makes the muscle more sensitive to the anabolic properties of protein feeding. So it, theoretically, it reduces your leucine threshold. So with a lesser increase in leucine, you would actually get a greater muscle protein synthesis. And of course, how I translate it is when you perform physical activity, the muscle is more interested in having enough building blocks than the signaling process, because the signaling process has already been fully activated by the exercise.

Rhonda Patrick: So here's another question for you. I know that exercise causes branched chain amino acids, like leucine, to be taken up into skeletal muscle, like from circulation. So, you know, leucine, these amino acids are doing lots of things in multiple tissues. Like, you know, it's going into the brain, it's getting transported in the brain, for example. But the exercise is causing, causes leucine, more leucine, to be taken up into skeletal muscle. So does that… I don't know if it's proper to even call it the leucine threshold, but, like, can you then, you know, take in more leucine and get it more into the muscle where it's like, where it used to be? Like, oh, after 3 grams or whatever, then you're not gonna really do much more. Do you think exercise would, in a way, almost make it where you could consume even more leucine?

Luc van Loon: Are you... If I. If I actually understand what you're saying, you're suggesting that the exercise induced lowering of the leucine threshold is potentially at least partly explained by greater leucine influx in the muscle. Yeah, that's possible.

Rhonda Patrick: Well, it kind of, it leads me to this next question that has to do with cardiovascular disease. And I'm sure you saw this, this headline that claimed high protein diets… It was an animal study that claimed getting 22% of your calories from protein was going to cause atherosclerosis. There was some human data in that study looking specifically at and identifying, they identified leucine as a major driver of this, because leucine in circulation activates macrophages, which are one part of the bigger, larger story in atherosclerosis. I was wondering what your thoughts are on. I know it's not your study, but on high protein diets, first of all, can you even translate that sort of study to humans when you're consuming 22% of your calories from protein and that's causing atherosclerosis?

Luc van Loon: I probably would not have seen the study, but it was actually in our papers, and I did get a, some questions about it from the general media. If I remember correctly, is I think the title of that paper was not that suggestive, but all the follow up reports on that paper were extremely suggestive and absolutely not in line with the outcome of the results in that study. So what they did is they provided, if I remember correctly, they provided two meals or two drinks. So they had something with a high protein content and a low protein content in humans. And then they took blood samples for, I don't know, a few hours after that meal. And then they actually took the monocytes, I think, so, the macrophages in the blood, and they saw that they actually were activated. And then they, they did an in vitro study to see which factor was actually stimulating the mTOR pathway in those macrophages. And that was leucine. Duh. I could have imagined that. It's with every tissue. And then they gave a high protein diet and a low protein diet to rodents, and they saw also activation of the macrophages, and that was suggestive of them developing arteriosclerosis.

Rhonda Patrick: Yes, and I think they had some other markers of arteriosclerosis as well.

Luc van Loon: But yes, but so, first of all, we're not rodents. And then the few hours of circulating amino acids is not reflective of what happens over days, over 24 hours, over weeks, over months, in the development of arteriosclerosis in humans. So I think that the translation is a little bit over the top. And that's an understatement. It's, with all these things, high protein is not causing any issues. High fat is not causing any issues. High glucose or high carbohydrate is not causing issues when it's only high and not excess. And that's a difference. The greatest problems with chronic metabolic disease is excess energy. Excess energy in the form of glucose, excess energy in the form of fat, excess energy in the form of protein–it's all bad. And we have, we have, all the mechanisms have been shown for glucose, fatty acids, and amino acids in, for example, inducing insulin resistance. If you oversupply a nutrient, at some point you become resistant to it, and that, and then the body doesn't know what to do with it, and you get issues. If your milkman comes by every day with two bottles of milk and you only drink one, it's not going to cost a lot more days before you start calling him to bring you less milk. That's what your muscle also does. At some point, it says, like, hey, I can't store more because this storage is hurting me. So it's not about high glucose or high fat or high protein. It's excess. Excess is the problem, right.

Rhonda Patrick: And that's where exercise and physical activity is key, because you are not only, I mean, most of the time, you are, of course, burning energy so you can consume more, but your muscles taking up glucose, it's taking up the protein, it's taking up leucine, so it's not in circulation, activating macrophages, right? So the exercise, and there's even been studies that have looked at, for example, you know, people that are consuming meat versus, you know, a vegan source of protein and how cancer mortality is higher in these meat eaters. It's all-cause mortality is higher in meat eaters. But when you then do a subgroup analysis and you say, okay, I only want the meat eaters that have no unhealthy lifestyle factors. So they're not sedentary, they're not overweight, obese, they're not smoking, and they're not consuming excess alcohol. Guess what? Their cancer mortality and all-cause mortality was the same as people consuming the plant protein. So if you are going to be unhealthy and obese and sedentary and smoke, perhaps you shouldn't eat a lot of protein–22% of your, your calories shouldn't be coming from protein. But certainly when you're physically active and you're healthy and you're not overweight and obese and you're not smoking, you probably shouldn't be worried about getting atherosclerosis by eating protein.

Luc van Loon: No, sometimes people misinterpret data, of course. I mean, you can say something like, hey, having a very high heart rate is not good, but why do you then exercise? Because that makes your heart rate go up, but then your resting heart rate goes down. So you have to get the full picture to understand. I mean, you challenge the body. I mean, exercise, I mean, I can make a statement, I mean, I can make a marketing statement that the worst thing to do for the body is actually doing exercise. You cause inflammation, you cause oxidative stress, it's really bad for you. It increases heart rate, but actually it sets off the whole process that makes you healthier. So just looking at what happens with one meal is not giving you the full picture of what it does for health.

Rhonda Patrick: I agree. Context matters 100%, and that's really important to keep in mind. And it's often the observational data and animal data that loses that.

Luc van Loon: I like the discussions, of course, of hypercaloric diets and overeating and under-eating in the light of animal experiments. I mean, we know that a lot of times when you have rodents in a cage and you give them ad libitum foods, they actually overconsume. I mean, we would do the same thing if you're actually sitting in a room and they're bringing you constant, just warm croissants and everything, you're going to overeat. So the animals do that as well, and then they give them a hypocaloric diet, or they give them less food, and then they're healthier. That's not necessarily that the hypocaloric diet was actually making them healthy. It is that the control trial is actually unhealthy, and we are that only controlled trial.

Rhonda Patrick: Yeah, I completely agree. I mean, it's. Yeah, it's so different when you're talking about a mouse in a cage that's sedentary and not physically active. And it's so hard to compare that sort of study to a physically active person, you know, as well.

Luc van Loon: But that brings us back to requirements. I mean, what are your real requirements? Because pure on definition, if they tell me, like, look, what will happen if I eat 25% less energy than I need? Then you die. But people become healthier when they eat 25% less. But that's something else. That is. It's not that they end eating 25% less than they need. They're eating 25% less than what they are actually used to consuming. And that's a huge difference between those two. And that's what we often, of course, don't want to see, because that makes our life more difficult.

Rhonda Patrick: Right. Their baselines are different. Talking about resistance training adaptations, this is another area that you've done a lot of research in. Can you tell people a little bit about muscle memory and how the muscle adapts to repeated bouts of resistance training?

Luc van Loon: Yeah. So the idea is that every exercise training induces stimulation of muscle protein synthesis and breakdown. So you recondition the muscle to become a better athlete in the next session. And next session. And next session. Of course, the additional value of each session becomes less because we can't keep improving. So there's a leveling off of that adaptation. Now, that's, in short, what training is. The every individual bout sets off this remodeling, and the remodeling becomes more efficient over time, and you become a better athlete. Now, the muscle memory is an interesting one, because then, now people suggest, like, okay, you haven't done anything for ten years, and then you start exercising. And then somebody that actually was a very good athlete builds up and becomes a much more rapidly increases his condition again, while the other one doesn't get the same gains now is that muscle memory, and if there is such a thing as muscle memory, where is it residing? Now, that's difficult, because then you actually, there's a lot of explanations. One, it could be genetics, that that person was already more active in the past because he was more prone to being a better athlete. That's a possibility. Secondly, that there's also something neuromuscular, that somebody picks up the exercise much easier and then gets bigger gains. It could be genetics, but then genetics or methylation of different proteins, and it could also be, and that's what they're now discussing. And Tim Snyders in our lab is actually doing a lot on that topic, is seeing whether the number of nuclei in the muscle are maintained to be increased. So it's easier for the muscle to adapt to exercise. Now, there's some rodent data to suggest that we don't find evidence for that in human muscle, so that you basically have more managers in your muscle fibers that when you put a greater stress on, it's more easily managed. But so far, we haven't seen that. So generally, we've seen that the myonuclear content and the myonuclear domain actually nicely follows exercise training. And it's not like it's completely different from somebody that actually did a lot of exercise in 20 years ago.

Rhonda Patrick: Now, you've also been involved in some research looking at exercise frequency. And, I mean, presumably recovery is part of that equation. In terms of if frequently working out and doing resistance training, like, is there a diminishing returns in terms of gaining muscle mass, is there a frequency that can be done to maximize muscle growth and also recovery?

Luc van Loon: Yes, likely, of course, you would like to get the full recovery and then the next training session. So you optimize the reconditioning process. And what you do notice, I mean, depends on how young you are, what training stage you are in. If. I mean, I haven't seen a gym last week, but before that, in a year or two or something like that. And then you go to a gym, and then you really notice that you need actually three days before you can actually get your next session in, when you're really in it, you actually train every day. So it depends on your training, state, your age, your genetics, what is your ideal version? The only way to figure that one out is just try it. There's no one rule to actually suggest that this is it.

Rhonda Patrick: In terms of recovery. Like, if you're working certain muscle groups, is it good to wait 24 hours, 48 hours? Is that still more of a personalized sliding scale, or…[inaudible]?

Luc van Loon: It is personalized, but of course, you can increase your, your session intensity by focusing on a specific group or upper body, lower body, or antagonist and agonists or something like that. So you can exercise more frequently and have enough, sufficient recovery time for each specific body part. That's a way that athletes use it to optimize recovery and maintain a high training load.

Rhonda Patrick: There are, you've published a study looking at an aging population. So you did elderly, but also you did older adults and then also elderly. So these are people like 85 years old, and you show they could have improvements in muscle mass and strength after engaging in a resistance training program. If there are some people out there who are older adults and elderly who perhaps want to start a resistance training program, are there any sort of exercises that you think might be just beneficial to start with for improvements in muscle mass and strength?

Luc van Loon: So the first thing to say is that the turnover of muscle, so the breakdown and the synthesis of muscle is something that occurs at one to 2% per day, as we started off this podcast with, and that is independent of age. So also, when you're 85, you still have, on a daily basis, you're making muscle and you're breaking down muscle. And the only way to maintain it or increase it is to do exercise. Now, the level of exercise depends on where you are at. So if you're actually quite sedentary and you have a lot of issues and you have difficulty getting up from the toilet, then it might make more sense to basically have two or three sessions a day where you try to get up from the toilet three times, simply on your own toilet, in your own environment, preferably with somebody to see that you're not falling, whereas there's also very, very fit elderly that will actually pick up resistance exercise and go to a gym three times a week. So nowadays, with healthy aging, it's very difficult to give advice, because the variation that we see in the elderly, we now are supposed to call it the older population, is huge. In the past, we got hip and knee surgery for people that were so in pain that they just wanted to have the pain to stop. Now we have older people coming in from new hips and new knees to go skiing with their grandchildren. So the targets set by the older population can be from staying in their own home, being able to go to the toilet unsupported, and therefore not being institutionalized, to 85-year-olds that still want to do an Ironman. So, of course, the training has to fit with the targets being set and where they start off from.

Rhonda Patrick: Yeah, that makes sense. I have a question regarding women and their response to adaptations from resistance training, either premenopausal versus postmenopausal, or post-menopausal, with or without hormone replacement therapy. So in other words, how the adaptations change with estrogen and progesterone and testosterone, more hormones around.

Luc van Loon: Yeah. So as we get older and we get hormone disbalances, then people feel differences. But the efficacy by which training increases muscle mass and muscle strength and muscle conditioning doesn't seem to have a huge impact there so far. I mean, this is not my topic, but most of the studies with pre and post-menopausal women, I believe, and even with and without supplementation, we see hardly any studies that I've seen don't show any differences. Now, we have a lot of experience with prostate cancer patients, so we've actually had a lot of prostate cancer patients on ADT. The first thing that happens when they are being diagnosed with metastatic prostate cancer is that they get androgen deficiency therapy. So basically, they get chemically castrated. So the testosterone will be gone down, just completely none. These people generally gain fat mass, lose muscle mass, and are at heightened risk for cardiovascular disease and often develop also insulin resistance and diabetes. Now, we thought like, hey, how easy is it to increase or prevent the muscle loss? To some extent, we were modest in this with only, like, two resistance exercise sessions a week. We increased muscle mass, we increased strength. Control group went down. There was no loss. There was actually an increase in muscle mass. There was an increase in muscle strength. So the hormones do not. I'm not saying that the hormones don't play a role because hypogonadal men, of course, in general, have less muscle, but exercise can fully overcome the effects of hormonal changes. Exercise is much stronger than that.

Rhonda Patrick: Yeah, it's just so powerful.

Luc van Loon: I mean, we had a lot of. So we worked this, of course, with the department, and we work with dialysis patients and we work with prostate cancer patients, and we see it every time, and everybody just says, like, why don't we just put this in our adjuvant therapy? Like, you can go on ADT, but ADT always goes together with resistance training. You have, I mean, the ADT is life saving, but then all the negative effects of the ADT can be completely, fully overcome with resistance exercise. That's ridiculous. Why do we still have those side effects if they're not necessary?

Rhonda Patrick: So testosterone does play a role in the context of these people that are not physically active, and then they start to lose more muscle. But you can basically attenuate that if you are..

Luc van Loon: You can even attenuate. So you can actually increase muscle mass and strength.

Rhonda Patrick: Right.

Luc van Loon: So it's greatly over exaggerated that the hormonal changes can be overcome with resistance. Exercise, that's the most important method.

Rhonda Patrick: There's a saying that our mutual friend Stu Phillips says, and I really like this saying, is that exercise forgives a lot of sins. And I'm seeing that recurring theme in not just exercise physiology, but in other fields as well. I mean, it's just sleep deprivation being one. I mean, insulin resistance goes up, glucose dysregulation, homeostasis, you know, out of control. But, you know, doing exercise mostly can rescue a lot of that. Even all-cause mortality increases. Again, physical activity really can forgive some of those sins. So it's really, you know, it's the best.

Luc van Loon: Even if it's not sins. I mean, even if it's disease, it can have so many benefits. Yeah.

Rhonda Patrick: I also think looking at it like, I just called it a medicine, but, you know, yes, exercise is a treatment, and that's like a general saying. You hear people say, exercise is a good medicine, but honestly, I think sedentarism is a disease.

Luc van Loon: I was just about to say this comes exactly back to the nutrition that we said, like, it's not excess carbohydrates. It's not a high carbohydrate diet, it's not a high protein diet, it's not a high fat diet. It's excess. And so. And we talked about the animals overfeeding and that the control group is actually an unhealthy group. We are unhealthy because we're not exercising enough. We are actually developed where we actually needed the physical activity in order to stay alive, to forage of our foods, and to hunt and stuff like that. And so it's not that… Maybe it's not the exercise is actually the benefit. It's actually reducing our–exactly what you're saying. Reducing our inactivity.

Rhonda Patrick: It's a disease. I think, you know, obesity is a disease. Type two diabetes, it's an occupational hazard. Sedentarism is a disease.

Luc van Loon: We're sitting.

Rhonda Patrick: Right. I mean, so I do want to kind of shift gears, because cold water immersion is an area that you have done research in, and I'm personally interested in the neuroendocrine effects of cold water immersion. A lot of physically active people are interested in using cold water immersion for recovery, for enhancing, sorry for a blunting inflammation of the muscle. But you've shown, and maybe you can talk about your study about, you know, doing cold water immersion immediately after resistance training can blunt some gains. Do you think the timing of cold water immersion can affect, you know, whether or not you're going to blunt those gains.

Luc van Loon: Because you want, you want to keep doing those cold showers? I'm doing those as well. So, yeah, I mean, I think with looking at heart rate variability and stuff like that, I mean, I've been experimenting with that myself as well, with the cold showers and the ice baths. But of course, from a muscle perspective, nothing makes sense on recovery after exercise, that cold would actually be helpful. So we did a study where we used the intrinsically labeled protein so we could track where the protein goes acutely, but also more long term. And after exercise, we put one leg in cold water and one in thermoneutral water. And we saw that the leg in the cold water did not get the same stimulation of muscle protein synthesis, and basically less of the protein would actually go to the leg, less perfusion, less stimulation of muscle protein synthesis. So from at least for the first six hours, it seems evident that acute recovery, recovery in the light of muscle protein synthesis, glycogen restoration, is actually compromised by the lower temperature. Part of that is that because you inhibit perfusion, but also, of course, all the enzyme and all the process activity in the muscle is also reduced by a lower temperature because that's just what happens. I was surprised that, I thought, like, hey, maybe then you compromise that acute recovery phase, but then you maybe catch up later on when you warm up, so that if you do this over two weeks, it doesn't make any difference. So we continue doing that for, if I'm not incorrect, over two weeks with six training sessions. And so it's six training sessions with only up to about 15 minutes of cooling. I thought that could never have an effect over those full two weeks. And if there's an effect, we wouldn't be able to pick it up, but we did. And over those two weeks, total protein synthesis in that leg that received cooling compared to the other was actually less and actually measurable less. So that six times 15 minutes cooling over two weeks, 14 days, 24 hours had a negative impact on the stimulation of muscle protein synthesis. My only conclusion is that the reconditioning is therefore not optimal. Now, if you still want to do the cooling, now the shower is only short, but would it be good to do it at different times? I think so. Why is everybody then still doing the cold water immersion after exercise? I think it came from sports where you basically hurt the muscle, where there's massive inflammation, where there's blunt force trauma on the muscle, that actually you basically support the muscle in recovery, not the reconditioning, but basically minimize the damage. And then people started using it for other sports as well. But I think for resistance training or for endurance training, you shouldn't be using it, at least not acutely, after the exercise session.

Rhonda Patrick: And you said something that I picked up on. You said for six hours. Do you think that if you do cold water immersion and you wait six hours after resistance training that you would still affect muscle protein synthesis? I mean, pure speculation.

Luc van Loon: I think it would be less, so, but then the other question is then for your other benefits, whatever they are. Of course, there's also a lot of discussions on that. Do you need to do that 15 minutes? Is it better to do it the other day? At least the first few hours, I think are essential for the muscle. I would stay away from the cold there. Is it okay to do it in the evening or the next day? I would favor that as opposed to the other one.

Rhonda Patrick: So waiting for recovery days. Now, you mentioned endurance training, but there are studies showing that cold water immersion can enhance performance and endurance trainers and also enhance neuromuscular function. You're talking about that? Probably not, as these people aren't… The resistance training is really stimulating muscle. So I'm wondering if you could do it perhaps on an endurance training day, maybe wait a few hours again.

Luc van Loon: I think we would have found exactly the same thing if we had done endurance training. So this was resistance training? I think if we had done endurance training, you would also have less of your amino acids that you ingest go to the muscle. I mean, a lot less of all this kind of work has been done after endurance training, but it seems to follow all the same principles. It's just the different sets of proteins that are being expressed to a greater or lesser extent after endurance versus resistance exercise. But they're also responsive to nutrition, and so they should also be responsive to blood flow, to the muscle. So I think it doesn't make a difference for endurance or resistance type exercise. The studies that I've seen is they either show no effect, and if they show effect, it's studies where that's not endurance exercise, it's actually high intensity, intermittent type exercise, where there's also a huge damage effect and inflammation. And I think there it can have a benefit to dampen that down and then acute performance afterwards is less compromised. But that's something else than optimizing your training, reconditioning, right?

Rhonda Patrick: Yeah. So you're talking more at the elite level where they're really like the rowers or the, you know, these runners that are, that are, you know, they're incurring more damage on their muscle. So the cold water immersion is causing vasoconstriction. It's preventing the muscle perfusion. The question is, how long does that last? So the norepinephrine is the hormone that is regulating that, as you know. And that does go up even after just two minutes in cold. So the question then goes, well, how long does that last? So, like, is it an eight-hour response? Do you think it would be 8 hours that it's going to be affecting?

Luc van Loon: I have no idea in this case. I mean, temperature at least skin temperature was already quite normal, quite fast, but the response over six hours was still visible. So, I mean, these studies are hard to do because then if you actually would do it this way, I would like to take a biopsy at two, four, six, eight, 12, 14, 16, 18, 22 and 24 hours. And of course, nobody wants to participate. Not even the older subjects in our studies are going to sign up for that.

Rhonda Patrick: Or at the very least, it would be interesting to do a cold water immersion where it's not immediately after resistance training. It's, you know.

Luc van Loon: Oh, yeah, I mean, that would be great.

Rhonda Patrick: Six, eight hours, maybe the next day.

Luc van Loon: If we would do that two week intervention study where you actually have the three sessions and now the six training sessions, and you have the six cooling sessions, and then you have the six cooling sessions on the days that you don't have the training. So you have three treatments. Six training sessions with cooling. Six sessions with cooling on the other day and only the six training without the cooling. That's a huge study, but I mean, I'll be interested to see what comes out after two weeks.

Rhonda Patrick: Yeah, I guess the question is that if you're doing resistance training and you wait six to eight hours after that training, will that cold water immersion blunt your gains? You said maybe a little bit, maybe not.

Luc van Loon: It will likely be less if you do it on the opposite day.

Rhonda Patrick: So waiting just on a recovery day is what I think is best.

Luc van Loon: But that's the whole thing. We always focus on muscle, but everything has to be optimal. I mean, it's the same as, oh, you can take creatine and you get stronger legs and you have a higher workload, but then if you're a high jumper and you gain 1.2 kilos, simply also by most of it actually water retention, it's not going to improve your high jumping. So it's more than only muscle, of course.

Rhonda Patrick: Of course. Yeah. I want to shift gears and talk about collagen last, because you've also been getting involved in some of this research, and I'm very interested in, in hydrolyzed collagen powder for skin, for example, and skin aging. And so I wanted to ask you if you think there are effects on supplemental hydrolyzed collagen powder that are independent of the muscle connective protein, which I think, if I'm correct, does not have a huge amount of collagen. But do you think there are effects in maybe other tissues, like the joints, skin, for example, bone?

Luc van Loon: That's a lot of questions. So collagen nowadays is much seen as a potential supplement to support muscle conditioning. And of course we were interested from that perspective. We often look at myofibrillar protein, which is the contractile proteins in the muscle, of course, because that's what, what generates the force. But you have to understand that the force that is generated by the contractile proteins has to be transferred towards your tendon and your bone in order to make movement possible. And so the muscle has a whole intricate network of connective proteins that allow the contractile apparatus to be transferred throughout the whole muscle, in both longitudinal as well as transversal way, towards the tendon and the bone. And there's now suggestions that strength is very much dependent on the quality of that connective protein network. And in muscle, that is, a lot of it is collagen. But if we get a fraction of the muscle is the connective proteins, and of those connective proteins, about 5% is collagen. And so we were interested to see whether collagen ingestion will actually stimulate that specific fraction in muscle. Now, so far, studies have not shown increase in muscle protein synthesis when you ingest collagen. Now, why could that be the case? Because it responds to high quality protein, but not to collagen. Now, collagen is from an amino acid composition, not a very high quality protein, because almost 50% is composed of proline and glycine, and so it has a lot less essential amino acids. And so if you give collagen protein, you generally don't see increase in mixed muscle proteins. We've done a study to see whether it increases connective protein in muscle. We don't see it, at least not with the 20 grams or the 30 gram amounts. Why would it work or why would it have an effect? Because the suggestion is, and that's the story behind it. There's actually two stories. One is that collagen has a lot of glycine and proline. And of course collagen is composed in your body, also a lot of glycine and protein. And maybe there's not a lot of those amino acids in our food, in our nutrition. But of course it doesn't matter that it actually increases muscle protein synthesis. So now we've tried it now, like three studies and so far we have not shown evidence that collagen increases connective tissue protein synthesis in muscle. But yeah, I have to admit that the muscle fraction is only a very small amount of collagen. So what about other tissues, cartilage, bone, tendons, ligaments, which is more than 80% collagen. Maybe there it's more relevant and maybe even more relevant when you had surgery and you basically yourself, you have to reattach everything. You have to renew all those collagen structures. Maybe there it is of benefit. Now there's also people suggesting that in collagen and especially hydrolyzed collagen, there's functional or peptides that are bioactive, bioactive peptides. So far we haven't seen anything of that. And there's always discussions like what are those peptides then? Haven't seen any data to convince me yet. And of course, it is not that the amino acids in collagen are now being used. We used intrinsically labeled protein, for example, to also show that the glycine or that the amino acids actually show up in collagen. So yes, collagen can be used and is a good source of glycine and protein. But does it further increase connective protein synthesis when compared to a high quality dairy protein or a different protein? So far we haven't seen any evidence for that. But of course, again, it's just a matter of the amount. If you give twice the amount of collagen, which has the same essential amino acids, than half the amount of, for example, egg or dairy protein, you might actually see exactly the same response. But there's a lot of studies that still need to be done to figure this one out.

Rhonda Patrick: It's interesting, there's been a lot of people that think that hydrolyzed collagen powder doesn't actually go to cartilage, but there's been some animal studies that have radiolabeled hydrolyzed collagen powder and it does go to cartilage. Do you think that's applicable? Like that's translatable to humans?

Luc van Loon: So the amino acids, I mean, so like I said, collagen contains, like any other protein, a lot of amino acids, and particularly the amino acids glycine and proline. And of course, those amino acids are going to be used to synthesize proteins, whether that's a connective protein or whether that's myofibrillar protein. So yes, this is just a protein source which has a lot of glycine and protein. So, yeah, why not? But from a complete constitution, it doesn't have as much as a balanced amino acid profile as most animal or higher quality animal derived proteins. But that doesn't mean that. I mean, I think, I mean, this is something that I think we... So, in muscle, I think that the availability of the amino acids is not restricting the increase after physical activity, because after physical activity, we see the connective tissue protein synthesis rates go up. But it doesn't seem to be dependent on the amount of protein or collagen that you provide. So I think there, it's not limiting, at least not in the first few hours after exercise, maybe in a longer timeframe. I don't know. That's possibility. I think the greater benefits are to be expected if they are there on the tissues that have a higher collagen content. And so I think there's still a window of opportunity there as a good source of glycine and proline for restoration or repair of collagen rich tissues, which could be skin, which could be tendon, cartilage, bone, etcetera. Whether it is of greater benefit than the same amount of amino acids provided by other protein sources, I don't know. But that's all stuff that we should start doing in the future. And we are actually doing a few of those studies. And we finished a few studies also, where we actually looked at skin, because skin is still easy to take samples from the other ones. We can only do that pre surgery. So we actually take people that get a new knee, and then we actually do the intervention prior to surgery. But of course, with skin, we can take a skin biopsy and we can take a muscle biopsy repeatedly over a few hours. And that's also stuff that we've done, but we still need to analyze everything.

Rhonda Patrick: What about the role, the signaling? You've been talking a lot about proline, hydroxyproline, glycine. I mean, these are amino acids that are certainly in greater quantity in something like hydrolyzed collagen powder versus a protein source from food or even a protein powder. But there's been a lot of, at least a lot of preclinical evidence looking at these small peptides being signaling molecules in their tissues. And there's been a lot of sort of, I would say, speculation that perhaps the signaling role of these collagen peptides may be as important, if not more important, than the incorporation of proline and hydroxyproline and glycine into tendons and skin.

Luc van Loon: So that's of interest. And, of course, it's really difficult to figure out in vivo in humans whether this is really happening, because, first of all, what di- or tri- or oligopeptides are you looking for? And then with having 20 different amino acids, you can almost have an enormous amount of different di- and tri- and oligopeptides. And even if you measure them in the circulation, do they actually come from the protein that you ingested, or were they newly synthesized in the liver? So it's so difficult figuring that one out. But it's really funny that I was in a podcast where somebody said, like, how do you get along with Professor Barr from UC Davis, who actually does a lot of this in vitro work? And so he must be your greatest enemy. And I said, do you want me to ping him to get him? And then the guy was completely just surprised. And he said, what do you mean? He said, he's in my office next door. He's on the sabbatical here. And so, actually, during the podcast, I actually got Keith out and we sat together. And then he thought that we had completely opposite perspectives, and we don't. I mean, I'm a human physiologist, and he's also a physiologist, but he looks at a lot of also ligaments, engineered ligaments, and looks at what happens there. But then the translation is, to what extent can you actually translate this to supplement use or stimulation in vivo? That… We're still far from that. Yes, the individual amino acids are important, whether there's bioactive peptides, I don't really see any evidence yet.

Rhonda Patrick: So, yeah, the thing that really piqued my interest in that was there's been a few studies looking at, like, very small amounts of hydrolyzed collagen powder, I mean, amounts that you would get in a pill in people with giving them either the hydrolyzed collagen powder or a placebo in people with arthritis. And the very, very small amount of hydrolyzed collagen powder was having an effect on reducing, you know, some of their. A lot of it's subjective, but there was also some inflammation that was reduced. And I was thinking…

Luc van Loon: I'm certainly not an expert on the topic, but I've seen a lot of those papers and a few meta-analysis and there seems to be going on something on pain perception. But of course, pain perception is also something very subjective. So is it working through the gut? Is it working through maybe gut-brain axis? Or is it really something between gut and muscle, or gut and musculoskeletal tissues? I don't know. But yeah, I mean, my outcome parameters are generally not pain.

Rhonda Patrick: That's why I brought up the signaling molecule as well, because it's like, when I saw the doses and these are placebo controlled, it was very surprising to me. I'm like, well that's a… It's got to be something else going on.

Luc van Loon: Yeah, I mean, we're giving like 20 or 30 grams of protein and then it's... If half of it is glycine and protein, those are huge amounts.

Rhonda Patrick: The last thing about the hydrolyzed collagen powder I wanted to talk about was getting your thoughts on, you know, so typically you can... Hydrolyzed collagen powder is available in a wide variety of sizes. So anywhere between two kilodaltons to ten. And there's some evidence that suggests perhaps that smaller, like two to five kilodaltons, those peptides are better absorbed, better used as signaling molecules, getting to the tissues better, like for example, skin getting smaller ones, like two to three kilodaltons. I mean, again, there's not an overwhelming amount of evidence on this. It's really up and coming and I think in its infancy. But I just wanted to get your thoughts and any speculation as to why smaller, perhaps not the ten kilodaltons, but maybe the two to five range might be.

Luc van Loon: So, quantitatively, most of the protein will be completely digested and absorbed as amino acids over the intestinal wall, then released in the portal vein, then actually released via the liver into the circulation. Now there are transporters for small peptides in the gut, and so they have been recognized and shown. The question is, do they then on the other side, do they stay in the intestinal cells? Are they released on the other side towards the portal vein? We don't really know that. And then what happens in the liver with them? So there are some evaluations of oligopeptides in the circulation. Are they directly coming from the ingested protein or the hydrolyzed protein? Is there a difference in their amount? Whether you have a further hydrolyzed collagen protein with smaller compounds? And we don't know, I mean, in vivo, I wouldn't have the guts to say it.

Rhonda Patrick: And what are your thoughts on the skin studies? That's one area where again, you mentioned tissues with a lot of collagen might be more important.

Luc van Loon: So sometimes people don't realize how little we know, because we know that if you provide protein and you see an increase in circulating amino acids, you see muscle protein synthesis increase. And I still think that's magical. I mean, I'm a complete nerd, of course, that I'm saying that, but do realize that you constantly have amino acids being released from the turnover. I told you that all those other tissues have a huge turnover, much higher than muscle. So there's constantly free amino acids being thrown in your circulation very rapidly. And then you only give like 20 grams of protein, of which 10 grams is released in the circulation over the next four hours. And that is only a spark, like maybe 15% on the total turnover, the release of amino acid in circulation. And that sets off a process that makes the muscle start synthesizing muscle protein. That's remarkable, because it's not a huge increase, it's on the top of everything, it's only a little stimulus. Now, we know this from muscle, we know how it works, we know what it does, and now we have the signaling molecules, the signaling pathways, we know the mTOR, we know leucine, etcetera, etcetera. We don't know anything about all these other tissues. So do the other tissues respond to nutrition or not? And that includes skin, but it also includes the liver and the heart, whatever. So the big question is, do these tissues respond to protein ingestion by greater muscle protein synthesis, or are they just having the same turnover, but they use, of course, the amino acids that are being released by the protein in our diet. So that's the big question. Now for skin, it's interesting because we can figure that one out, because I can't take three samples of the liver or the lung or the brain in six hours. That's impossible. I can maybe obtain one sample after like a two hour surgery for the skin. Of course, we could actually do the same thing as muscle. And now I'm not that much interested in skin. But if skin is actually an easier way of finding this, investigating the same process as muscle, that's interesting, because then we only have to take skin biopsies, which is much easier than taking muscle biopsies. So I'm really interested to see what comes out of that study.

Rhonda Patrick: Well, the other interesting thing too would go back to that signaling role, because again, I've seen, and this is, as you mentioned, largely in vitro, when scientists are looking at mechanistic potential explanations is that these collagen peptides that are small, they're decreasing matrix metalloproteinases that are breaking down collagen, they're increasing enzymes that are synthesizing collagen in the skin, like these are in skin cells, fibroblasts.

Luc van Loon: But the big question is, we've seen people, there's people doing in vitro work with all kinds of compounds, throwing them in the dish and seeing something happening. But does the muscle see those compounds? That's one. And in what concentration?

Rhonda Patrick: Absolutely.

Luc van Loon: And that's where it's limited. So a lot of that research has not been done. And to be honest, a lot of the collagen research is still in, how do you say that? Children's shoes or baby shoes. It's basically, it still has to happen. I mean, it took us many years to convince people to co-support in public private partnerships, these kind of studies to see what are the benefits of, of collagen. Because I mean, the story can be good, but we need to verify it. But of course, it's always scary because what if it doesn't do anything? What if. And that's always what restricts science, of course, because I mean, science is costly, but I think the studies just need to be done.

Rhonda Patrick: Do you think there might be beneficial aspects to consuming a type of which you in some ways called low protein source because it doesn't have all the great. Yeah, low quality protein, it doesn't have all the great amino acids for skeletal muscle protein synthesis. But, you know, proline, hydroxyproline, glycine, it's high in arginine. Arginine plays a role in our vascular system. Like do you think there could be a role just for consuming hydrolyzed collagen powder just for those amino acids that are a little more abundant in that type of protein source?

Luc van Loon: If there's an unbalanced need for specific amino acids, then of course a source that is richer in those amino acids might be of benefit, but those amino acids can also be provided by other protein sources, of course. But then again, it's a matter of you compensate with greater quantity in order to get the same amino acids in. And so what I think and what I would like to do to study, but we're not doing that yet after large orthopedic surgery where the collagen is actually a benefit to resynthesize all those collagen rich tissues, because then knowing that 50% is glycine and proline of these tissues, that's a lot of glycine and proline. So maybe in those conditions, you need sources of extra glycine and proline. And then, I mean, then you might actually have a benefit of taking collagen supplements, but, of course, you could also get that by your normal nutrition. But there are some interesting calculations and assumptions that nowadays our diet is low in, for example, glycine and proline because we're not consuming bone broth anymore and stuff, and a lot of our food is processed. I mean, so the story is still there. I mean, the science is not there to back it up yet.

Rhonda Patrick: Yeah, I don't know that most people are consuming high amounts of proline and glycine and hydroxyproline from food sources, unless they are eating the cartilage of their chicken and boiling the bone broth. I mean, yes, some people are doing that, but the general population is not. And so it is easier to take a hydrolyzed collagen powder, which has a much higher concentration of those specific amino acids, than eating a steak.

Luc van Loon: Yeah. What I often also hear, I mean, the hydroxyproline, that might have a… I mean, that actually is increased in the circulation after ingesting collagen, but the hydroxyproline is not a precursor for your incorporation in your own collagen. But it might have a stimulatory effect or signaling effect. But we don't know. I mean, again, what does the muscle see? What does those other tissues see? What does the synovium see? The only thing that I mean, to be honest, I mean, about, I think four or five years ago, I think that we were the first to assess the synthesis rate of all the proteins in and around the knee. So what we did is we infused people before they underwent full knee surgery, and we measured the synthesis rate of muscle, cartilage, synovia, menisci, the ACL, the PCL. So everything there was really funny, because normally we take a muscle biopsy and then we have 150 milligrams of muscle and we're completely happy, and then we have to measure all these different things in that small amount of muscle. Now you're standing in the surgery room and you're getting a whole mixed grill. I mean, I'm getting a meniscus, I'm getting an ACL and PCL, I'm getting all this tissue, and I can measure this and this and this. Now we have a whole spectrum of all the tissues in and around the knee, and the synthesis rates were almost all in the same ballpark as muscle. And I thought that was already, for me, the first step towards nutrition in these tissues, because the regenerative capacity of these tissues is higher than anticipated.

Rhonda Patrick: Do you know of a role that growth hormone plays in collagen synthesis in…?

Luc van Loon: Yeah. So we know that, especially from abuse, of course, that the growth hormone has, in combination with, for example, anabolic steroids, can help you with the connective tissue protein synthesis and stuff like that. So, yeah, not sure whether to suggest that you have to combine it with collagen peptides or anything like that.

Rhonda Patrick: Yeah, but I mean, you increase growth hormone with exercise.

Luc van Loon: Yeah, yeah. Also increase testosterone. But like I said, I mean, the exercise is much more potent than the hormonal changes that you see.

Rhonda Patrick: Right. Well, thank you so much, Luc, for this very enlightening conversation, for all your research that you've done before we, you know, before we leave, I'd like to ask one last question about your personal routine. I mean, how you apply maybe some of the principles you've learned through your research and others for your nutrition, your exercise, workout, frequency, I mean, what you aim to do, perhaps what you do and what you aim to do.

Luc van Loon: In general, when people ask me, I always say I try to not to mix work with private life, but that's just a cop out. No, I ride my bike a lot, Holland. So I'm sitting on a road bike a lot, especially in the summer. I don't have a specific. I don't have specific targets. I exercise basically to keep everything as healthy as possible and that I can then indulge myself with more food and I don't get too fat. So I cycle maybe like four or five times a week and longer rides in the summer when the sun is out. I used to ride in the rain, but now I don't do it anymore. I'm getting lazy. And, of course, some resistance training. That's not the amount that I did in the past. I mean, now it's maybe one or two sessions a week.

Rhonda Patrick: And as I heard from you say early, you mostly don't eat a lot during the day and then eat most of your…

Luc van Loon: Yes, but that's not a good thing. I have to change that, to be honest.

Rhonda Patrick: Well, thank you so much, Luc, for coming on the show and talking about your research and the importance of protein and resistance training in muscle physiology.

Luc van Loon: Thanks for having me.