#68 Dr. Bill Harris on the Omega-3 Index, Increasing Omega-3 to Improve Longevity & Heart Disease Risk

Posted on December 7th 2021 (over 3 years)

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Dr. Bill Harris is one of the world's preeminent experts in the field of omega-3 fatty acid research. His work focuses on the roles that fatty acids play in cardiovascular and neurocognitive health.

The author of more than 300 scientific papers on fatty acids and health, Dr. Harris is a professor in the Department of Medicine in the Sanford School of Medicine at the University of South Dakota, the co-inventor of the Omega-3 Index, founder of OmegaQuant Analytics, and president and founder of the Fatty Acid Research Institute.

In this episode, Dr. Harris and I discuss...

  • How early studies on dietary fats and cholesterol levels spawned the field of omega-3 research.
  • How flaws in early study designs may have led to inconsistencies in findings.
  • How pre-operative omega-3 loading reduces blood loss during surgery.
  • How standards of "normal" bleeding time may be abnormally high in Western countries.
  • How different types of omega-3s share structural similarities but not cardioprotective effects.
  • How genetic engineering of plants may yield abundant, sustainable omega-3s in the future.
  • How the Omega-3 Index was created.
  • How red blood cell concentrations of omega-3s better reflect long-term omega-3 status than plasma measures.
  • How known genetic variants, such as those in the FADS gene, influence omega-3 needs to some degree, but don't yet fully explain interindividual variations in metabolism.
  • How people with high omega-3 concentrations are less likely to die prematurely.
  • How byproducts of omega-3 metabolism called specialized pro-resolving mediators reduce inflammation.
  • How people with high omega-3 concentrations are half as likely to die from COVID-19.
  • How concerns over the omega-6/omega-3 ratio may be overblown.

Decades of omega-3 research and seminal discoveries

"People were very excited. By that time, the work of the Danish investigators Dyerberg and Bang linking omega-3 with reduced atherosclerosis – that was becoming well known then."- Dr. Bill Harris Click To Tweet

Fifty years ago, Danish scientists Hans Olaf Bang and Jørn Dyerberg embarked on an icy journey to the remote coastal regions of northwestern Greenland. They wanted to understand why the Inuit, the area's Indigenous people, had the world's lowest incidence of cardiovascular disease-related deaths despite their high-fat diet, which was rich in seal meat and fatty fish.

Bang and Dyerberg's research revealed that the average Inuit had lower triglyceride and lipid concentrations than the average Dane. But the Inuit's concentrations were also lower than their Inuit peers living in Denmark, suggesting that environmental factors, rather than genetic ones, were at play.

Subsequent research revealed that the Inuit living on Greenland had high blood concentrations of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), a pair of long-chain polyunsaturated fatty acids. Bang and Dyerberg posited that these fatty acids, commonly known as omega-3s, were the secret to the Inuit's health. Although the study’s claims about heart disease rates in the Inuit have since been called into question, those early findings provided a catalyst for an extensive field of research that continues today.

Omega-3s had captured the interest of scientists in the United States, too, including Dr. William ("Bill") Connor, a pioneer in the fields of lipid nutrition, cholesterol metabolism, and atherosclerosis. Dr. Connor encouraged Dr. Harris to pursue the study of omega-3s, launching a career of study spanning 40 years exemplified in more than 300 publications.

Omega-3s influence multiple aspects of human health.

"Some studies have not shown an effect. Partly it's low dose, partly it's background omega-3 levels are higher in the population, and they haven't controlled for that. Partly it's short-term treatment." - Dr. Bill Harris Click To Tweet

Since those early studies, scientists have conducted hundreds of investigations examining the health effects of omega-3s. The research has revealed that these important fatty acids are involved in nearly every aspect of human physiology, exerting a wide range of effects on multiple organ systems and influencing cardiovascular, neurocognitive, immunological, and respiratory health, among others.

Epidemiological data have identified robust links between omega-3 intake and reduced risk of premature death. But the findings from the five decades of study have been remarkably inconsistent, with some studies showing benefits, and others not. Some of these inconsistencies have arisen from differences in study designs, which vary markedly in terms of study population, dose, and duration.

Multiple mechanisms drive the beneficial effects of omega-3s

"But we found that if you give people 10 grams of omega-3 [three or four days], before surgery, they actually [had] less post-op bleeding. Less need for transfusion, which was kind of cool."- Dr. Bill Harris Click To Tweet

In the early days of the research, scientists believed that the mechanisms driving the cardioprotective effects of omega-3s were related to their capacity to reduce platelet aggregation – an important stage in the atherogenic process. As a result, many of the early studies focused on this phenomenon. The research demonstrated that omega-3s extended bleeding time, slowing clot formation, an effect often referred to as "blood thinning."

Does omega-3 supplementation create bleeding risks?

"It was a surprise. Makes me think that when we say you're prolonging the bleeding time, maybe you're moving it toward normal or optimal." - Dr. Bill Harris Click To Tweet

These blood-thinning effects raised concerns that the fatty acids might cause excessive bleeding following trauma or during surgery. But those concerns haven't panned out, and data indicate that the effect of omega-3s on bleeding time is similar to that achieved with aspirin, the drug of choice for most people at risk for clots. In fact, evidence suggests that preoperative omega-3 loading reduces blood losses during surgery. Interestingly, in Japan, where fatty fish intake is high and most people have high blood omega-3 concentrations, bleeding time is rarely a concern. Dr. Harris posits that the standards of "normal" bleeding time among people who follow a Western dietary pattern (which is low in fatty fish) may be skewed toward an unfavorable status.

"[EPA and DHA are] not just anti-inflammatory, they're pro-resolving of inflammation. If you don't have the omega-3s onboard, the inflammation stays longer." - Dr. Bill Harris Click To Tweet

More recent research has revealed another mechanism that likely drives the health effects of omega-3 fatty acids – a large class of unique byproducts of omega-3 metabolism called specialized pro-resolving mediators, or SPMs. Scientists have identified four families of SPMs, including the resolvins, lipoxins, protectins, and maresins. These remarkable and diverse molecules reduce the inflammation that drives many chronic diseases, promote apoptosis, regulate leukocyte (white blood cell) activity, and reduce the production of proinflammatory mediators.

Unique qualities of the marine omega-3 fatty acids EPA and DHA

There are several omega-3 fatty acids, but the ones that have the greatest relevance for human health are the two identified in the Inuit's blood – EPA and DHA – as well as alpha-linolenic acid (ALA), which is found in a wide variety of seeds, nuts, and their oils. These omega-3s share structural similarities but differ in their cardioprotective effects. For example, EPA and DHA play particularly important roles in heart health because they participate in pathways involved in the production of hormones that regulate blood clotting and inflammation, help maintain healthy heart rhythms, and influence the contraction and relaxation of arteries. ALA benefits heart health, too, but to a lesser extent, and may reduce the risk of stroke.

Omega-6/omega-3 ratio

"You cannot improve your health by leaving your omega-3 intake alone and just lowering your omega-6. There's only one way to fix it: eat more EPA, DHA." - Dr. Bill Harris Click To Tweet

Chemical cousins to the omega-3s – the omega-6s – often get a bum rap, but they provide health benefits, too. And although older studies showed that the ratio of omega-6s to omega-3s in blood were cause for concern, Dr. Harris explains that those concerns are likely unfounded. Rather than focusing on decreasing omega-6 intake to improve the ratio, most people would probably benefit from increasing omega-3 intake instead, he says, to improve overall blood concentrations.

Quantifying human omega-3 needs presents challenges

How much omega-3 do humans need to get for optimal health? That's a difficult question to answer. Nutrition experts haven't established a recommended dietary allowance for the omega-3s; rather, they suggest an "adequate intake" of 1.1 grams per day for females and 1.6 grams for males. And many public health authorities simply recommend eating at least two servings of fish per week, providing a minimum average of only about 300 to 450 milligrams daily.

"We're looking at the omega-3 index and predicting risk for Alzheimer's and dementia. The relationship is stronger in those that have higher risk, that is, have APOE4, than those with low risk." - Dr. Bill Harris Click To Tweet

The reluctance to establish firm guidelines is likely because determining the optimal intake of omega-3s is complicated. Dietary and supplemental forms of the fatty acids differ in their content and quality, and people may carry genetic variants or exhibit other factors that influence not only blood concentrations but also individual responses to omega-3s. For example, people who carry a particular variant of the APOE gene, called APOE4, respond well to the DHA present in fish but not as well to dietary supplements, possibly due to impaired transport of the form of omega-3s commonly present in supplements. However, robust evidence indicates that a combined dose of EPA and DHA between 1.75 and 2.5 grams per day can help most people achieve omega-3 concentrations of about 8 percent – a level generally associated with improved health outcomes.

The Omega-3 Index is a marker for cardiovascular risk

"But interesting to me is that all these other causes of death – from electrocution to suicide, to car accidents, to kidney failure, you know, everything people died of – the higher the omega-3, the lower the risk."- Dr. Bill Harris Click To Tweet

Dr. Harris and a colleague, Dr. Clemens von Schacky, recognized the need to quantify blood concentrations of omega-3s that increased (or decreased) risk for cardiovascular disease and related death. They identified a target omega-3 level, dubbed the "Omega-3 Index," that serves as a measurable risk factor for sudden cardiac death. Unlike traditional omega-3 assays, which measure omega-3s in plasma or phospholipids, the Omega-3 Index gauges the fatty acid concentrations in red blood cells. It's a better indicator of long-term omega-3 exposure, says Dr. Harris, analogous to the HbA1c test for long-term blood glucose concentrations.

Dr. Harris and a team of researchers recently reviewed data from 17 studies investigating links between blood concentrations of omega-3s and the risk for all causes of premature death. The studies included more than 42,000 adults (average age, 65 years) living in 10 countries. They found that participants with the highest blood concentrations of EPA and DHA combined were 18 percent less likely to die from all causes of premature death, compared to those with the lowest levels. When they analyzed death rates by specific causes, they found that those with the highest blood concentrations of EPA and DHA combined were 20 percent less likely to die from cardiovascular disease and 13 percent less likely to die from cancer.

Is there a role for omega-3 in reducing COVID-19 severity?

An emerging area of interest in omega-3 research centers on immunity, specifically against SARS-CoV-2, the virus that causes COVID-19. Recent data suggest that people with high omega-3 blood concentrations are half as likely to die from COVID-19 compared to those with low concentrations.

In silico experiments (also known as computer modeling) demonstrate that the mechanism driving the fatty acids' protective effects may be related to their effects on the spike protein – the primary antigenic component of SARS-CoV-2. The spike protein can assume two different spatial arrangements – a closed, or "pre-fusion" arrangement, or an open, "post-fusion" arrangement. When the spike protein binds to ACE2, it must change from its pre-fusion structure to a post-fusion one. The computer models showed that DHA keeps the spike protein closed, potentially reducing viral entry into cells. These findings, if replicated in in vitro studies, can have huge relevance for managing the global pandemic – and saving millions of lives.

A robust and growing body of evidence demonstrates that omega-3 fatty acids are essential nutrients that play critical roles in multiple aspects of human health. In this episode, Dr. Harris and I discuss the importance of omega-3s, the mechanisms that underlie their effects, and how quantifying them may help identify people who are at risk for cardiovascular disease.

Learn more about Dr. Bill Harris

Relevant publications

People mentioned in this episode

  • Dr. Bill Conner (deceased)
  • Dr. Hans Olaf Bang
  • Dr. Jørn Dyerberg
  • Dr. Scott Goodnight
  • Dr. Mozaffarian
  • Dr. Clemens von Schacky
  • Dr. Christine Albert
  • Dr. Charles Serhan
  • Dr. Ronald Krauss
  • Dr. Theodore Brasky
  • Dr. Michael Davidson
  • Dr. Bruce Ames
  • Dr. Kristina Jackson
  • Dr. Philippa Middleton

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