Prolonged fasting as a powerful way to regenerate and rebuild systems | Valter Longo
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During prolonged fasting or starvation, the body survives by eliminating unnecessary cells via apoptosis, the process of programmed cell death. These cells will be replaced when food becomes available. This regeneration process, the most extensive since birth, is a powerful feature of prolonged fasting. In this clip, Dr. Valter Longo describes how prolonged fasting and subsequent refeeding, sends signals to the body to systematically shrink and rebuild organ systems.
Rhonda: You mentioned the regeneration of the stem cells, so that's the study that you're referring to. You did this prolonged fasting for, I think it was like 48 to 72 hours in animals, and you showed that during that fasting state the white blood cells were...basically their populations decreased. And the reason they had decreased was because something was being activated called autophagy, which is the clearing away of damaged cells. And somehow, so the autophagy that happened, you're saying that after that occurred, that was the signal for the regeneration of the stem cells or the refeeding after?
Valter: Yeah. Autophagy is clearly occurring, and this is established for fasting. But we don't think, I mean...what we've done so far was...now we're focusing more on autophagy, but what we done so far was more about, if you have an immune system, a complete immune system, that immune system has a lot of cells that you don't really need, right?
Rhonda: Mm-hmm.
Valter: So, during starvation, whether you're a mouse, and now we know the same to be true for people, you have to get rid of a lot of cells, a lot of things that you don't need. And that's what's happening, it's not so much about autophagy, but it's more about apoptosis, and so, a program cell death. You're killing, essentially giving rid of a lot of cells, and then you stand by, you wait until food comes around again, and you rebuild it. So, for example, in a mouse, about 40% of the white blood cells are destroyed during this period of four days of fasting or so. And then, that 40% is rebuilt within a few days of refeeding, right? So, it's really extraordinary and probably the most powerful regeneration or generation program that you have since birth, essentially, right?
So, when a baby is first born, of course, you're generating all these systems. But then, that never happens again, right? Not in that way. Like, for example, the liver being generated, and the lungs being generated, and the heart, etc. So, fasting is probably the most powerful, at least, that we could think of. The most powerful way, particularly if it's prolonged, to shrink a system, let's say, make the liver a lot smaller, make all these organs a lot smaller, the immune system, and then regenerate it, right? And so, this is why we think it's so powerful because it is not really the fasting that is doing anything, it is the body that is doing everything. The fasting just tells the body, "I need you to kill all these cells," and then, the refeeding gives the message, "I need you to rebuild all the systems cells."
Programmed cell death. Apoptosis is a type of cellular self-destruct mechanism that rids the body of damaged or aged cells. Unlike necrosis, a process in which cells that die as a result of acute injury swell and burst, spilling their contents over their neighbors and causing a potentially damaging inflammatory response, a cell that undergoes apoptosis dies in a neat and orderly fashion – shrinking and condensing, without damaging its neighbors. The process of apoptosis is often blocked or impaired in cancer cells. (May be pronounced “AY-pop-TOE-sis” OR “AP-oh-TOE-sis”.)
An intracellular degradation system involved in the disassembly and recycling of unnecessary or dysfunctional cellular components. Autophagy participates in cell death, a process known as autophagic dell death. Prolonged fasting is a robust initiator of autophagy and may help protect against cancer and even aging by reducing the burden of abnormal cells.
The relationship between autophagy and cancer is complex, however. Autophagy may prevent the survival of pre-malignant cells, but can also be hijacked as a malignant adaptation by cancer, providing a useful means to scavenge resources needed for further growth.
A type of intermittent fasting that exceeds 48 hours. During prolonged periods of fasting, liver glycogen stores are fully depleted. To fuel the brain, the body relies on gluconeogenesis – a metabolic process that produces glucose from ketones, glycerol, and amino acids – to generate approximately 80 grams per day of glucose [1]. Depending on body weight and composition, humans can survive 30 or more days without any food. Prolonged fasting is commonly used in the clinical setting.
[1] Longo, Valter D., and Mark P. Mattson. "Fasting: molecular mechanisms and clinical applications." Cell metabolism 19.2 (2014): 181-192.
A cell that has the potential to develop into different types of cells in the body. Stem cells are undifferentiated, so they cannot do specific functions in the body. Instead, they have the potential to become specialized cells, such as muscle cells, blood cells, and brain cells. As such, they serve as a repair system for the body. Stem cells can divide and renew themselves over a long time. In 2006, scientists reverted somatic cells into stem cells by introducing Oct4, Sox2, Klf4, and cMyc (OSKM), known as Yamanaka factors.[1]
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