#83 – Bill Harris, Ph.D.: Omega-3 fatty acids

"I don't think [omega-6] is the evil that people think it is. The problem is that we need to get more EPA and DHA in our diet, not necessarily get all hung up on omega-6." — Bill Harris

Read Time 26 minutes

In this episode, Bill Harris, Ph.D. in human nutrition and expert on omega-3 fatty acids, sets the table by clearly defining the families of fatty acids (saturated, monounsaturated, polyunsaturated) before diving into the current landscape of polyunsaturated fat (omega-6 and omega-3) with a particular focus on EPA and DHA (the two main elements of fish oil supplements). Bill gives a historical overview, updates us on the latest science related to the health benefits, and provides plenty of insights as to how we should think about increasing our EPA and DHA intake.


We discuss:

  • Bill’s long history of studying fatty acids [6:30];
  • Defining the fatty acids—SFA, MUFA, PUFA, omega-3, omega-6, and more [9:45];
  • What is the significance of fatty acids? Why should we care? [19:45];
  • History of fat phobia, saturated fat, and does PUFA reduce cholesterol? [23:45];
  • Breaking down the conversion process of omega-6 and omega-3 fatty acids including how we get to EPA and DHA [28:00]; 
  • Takeaway from Bill’s 1980 study looking at how salmon oil affected cholesterol and triglyceride levels [36:15];
  • History of our understanding of omega-3 and its effect on LDL cholesterol [45:00];
  • Prescribed fish oil drugs vs. OTC supplements—Differences and recommended brands [52:00];
  • Health benefits of EPA [57:45];
  • Potential benefits of ALA and how it compares to taking EPA and DHA directly [1:12:45];
  • Health benefits of DHA [1:17:15];
  • Cell membrane omega-3 index—What is it, the role of genetics, how to increase it, and a recommended target [1:19:00];
  • Is EPA or DHA neuroprotective? Can it help with depression? [1:23:30];
  • Recommended fish to eat for EPA and DHA – Any mercury concerns? [1:25:45];
  • Can omega-3 mitigate risks associated with smoking? [1:29:15];
  • The problem with the omega-6 to omega-3 ratio [1:30:00];
  • The problem with labeling any kind of fatty acid as “bad” [1:36:00];
  • Why increasing EPA and DHA intake matters more than reducing omega-6 intake [1:38:00];
  • Important takeaway from the VITAL study [1:46:30];
  • Importance of testing your omega-3 index [1:53:00];
  • Exciting study coming out soon, and why you need to take your fish oil with food [1:57:15]; and
  • More.


Bill’s long history of studying fatty acids [6:30]

  • Got a PhD in nutrition in 1978
  • In post-doc, worked for Bill Connor in Portland, Oregon 
  • First assignment was to figure out what the effect is of salmon oil on cholesterol levels
  • Did a metabolic ward study in the late 70s
  • Fed people huge amounts of salmon steaks plus salmon oil (~25 grams of EPA/DHA per day)
  • Lasted 28 days
  • Found that the salmon oil did lower cholesterol relative to the saturated fat diet 
  • It was about the same lowering as we saw with the vegetable oil diet
  • The thing that was unique about salmon oil was that it lowered triglyceride levels
  • Published these results in 1980
  • Around that same time, Hans Olaf Bang and Jorn Dyerberg published a series of Greenland Eskimo studies which were becoming well-known

“And so we started chasing omega-3 effects on lipids and platelet function and all kinds of other things, and so I’ve just been able to stay with it. I’ve had five grants from the NIH to study omega-3 related questions. It’s been a field that’s continued to be fascinating and ups and downs, but enriching, and as you said, it’s confusing right now. It’s been confusing for most of its history.”


Defining the fatty acids—SFA, MUFA, PUFA, omega-3, omega-6, and more [9:45]

Fat is one of the five macronutrients

  1. Fats
  2. Proteins
  3. Carbohydrates
  4. Ketones
  5. Alcohol

Fats come in different chemical forms:

  • Saturated fat
  • Monounsaturated fat
  • Polyunsaturated fat
    • PUFA is then divided further
      • Omega-3
      • Omega-6
      • Omega-9
      • And more.

Saturated fatty acid (SFA)

  • SFA are a long single chain of carbon atoms all hooked together (single bonds)
  • In chemistry, you can have single bonds, you can have double bonds, you can have triple bonds
  • The vast majority of fatty acids in butter, for example, have long single chain
  • Solid at room temperature: The simplest way to detect the saturated fat is at normal room temperature, they’re solid

Figure 1. Saturated fatty acid. 

Monounsaturated fatty acids (MUFA)

  • These have the same long carbon chain as…

{end of show notes preview}

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Bill Harris, Ph.D.

Dr. Harris is an internationally recognized expert on omega-3 fatty acids and how they can benefit patients with heart disease. He obtained his Ph.D. in Human Nutrition from the University of Minnesota and did post-doctoral fellowships in Clinical Nutrition and Lipid Metabolism with Dr. Bill Connor at the Oregon Health Sciences University.

His interest in omega-3 fatty acids began with his postdoctoral work when he published his first study on the effects of salmon oil on serum lipids in humans (1980). Since that time he has been the recipient of five NIH grants for studies on the effects of omega-3 fatty acids (EPA and DHA) on human health. He has more than 300 publications relating to fatty acids, including omega-3s, in medical literature and was an author on two American Heart Association scientific statements on fatty acids: “Fish Consumption, Fish Oil, Omega-3 Fatty Acids and Cardiovascular Disease” (2002), and “Omega-6 Fatty Acids and Risk for Cardiovascular Disease” (2009) both published in the journal Circulation.

Dr. Harris is a Professor in the Department of Medicine in the Sanford School of Medicine at the University of South Dakota and the President and CEO of OmegaQuant.


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  1. very interesting podcast. Thank you! Can you followup with Bill and ask about the algae-based Omega-3 products (seaweed extract)? Claim a better DHA/EPA ratio than fishoil (plus no mercury concerns). Product I’m taking is Testa Omega-3 but there are several on the market. Just curious as if I’m wasting my money… Cheers!

  2. I tried taking DHA supplements (I think it included EPA too) about 10-15 years ago but it left me feeling like I had a brain fog and some insomnia. Also, starting in 2008 I started catching wild Sockeye Salmon from the Copper River. Locally we call them Red Salmon and the Copper River salmon are famous for their high oil content. If I eat a lot of sockeye salmon I also get the same brain fog feeling. So starting in 2008 until about 2015 I ate lots of these oily salmon, probably on average 3 times weekly. Usually we caught on average about 30 salmon each summer–but one year I got 55. I had a coronary calcium score of 101 in 2008. By 2019 it went up to 442. So the high amount of oily wild sockeye salmon I ate does not appear to have protected my coronary arteries.

    • @Lance Gillette

      While I don’t know enough about calcium scores or how EPA/DHA are mechanistically protective to offer much advice, are there other dietary/lifestyle factors that aren’t being controlled for that could help reduce your calcium score?

      @Peter Attia
      Great podcast. I’m sure I don’t get enough EPA and DHA in my diet and apparently reducing omega 6 (which in my diet only comes from nuts and trace amounts from animal sources) isn’t the proper way to correct for a deficiency in EPA/DHA. I’m still skeptical that over consumption of Linoleic acid over time isn’t inflammatory in nature, though I doubt long term controlled studies exist. If Harvard health says omega 6’s are okay, I’m bound to be skeptical.

      • 100% agreed regarding linoleic acid. Listening to Bill Harris whitewash the painful obvious role that extreme amounts of linoleic acid / omega-6 PUFAs have had on our metabolic crisis was painful.

        Not once does he mention what happens AFTER you have too much Arachidonic Acid (–> HNE, the real killer).

        Yet repeatedly we hear about all of this LA coming from our diets in SOYBEAN OIL, something that never existed before this crisis (~50 years), is nearly completely unnatural, and brings morbidity with it everywhere it goes. Bill talks about soybean oil like it’s a natural part of a human diet or something. Come on.

        He also doesn’t realize that saturated fat has an omega-3 sparing effect. Of course I agree that Omega-3 should be increased in most Americans though. Not wrong there.

        Thanks to Peter for clearly giving a “read between the lines” style comment that he never eats those disgusting seed oils. Peter knows.

        It’s time to bring someone on to rebut this portion of the conversation.

        • Peter did a great job slipping that comment in there. I was taken back by hearing Bill’s stance on these but glad Peter cleared it up. I thought I was going to have to look more into this to see if I have been wrong this whole time!

        • I was thinking exactly this. Peter’s subtle rebuke was spot on. I would love to see Peter have a discussion with Chris Knobbe regarding these Omega 6 PUFA’s.

      • I think this illustrates the unfortunate myopia that’s a side effect of being a lifelong researcher. Bill may well be the leading expert on EPA but the research presented here is highly specialized and none of what he said accounted for a zoomed-out view of lifestyle factors, interactions between other aspects of diet (i.e. saturated fat’s sparing effect), the sum total of literature on linoleic acid, etc. Science has become, unfortunately, extremely deep but extremely narrow.

  3. Omega 6 may be OK as long as it hasn’t oxidised or been used for cooking. I guess in these studies, it’s given as an oil in a capsule or to be drunk as opposed to being used in cooking. In New Zealand canola oil from takeaway outlets is used to manufacture mascara and lipstick as the repeated heating of the oil causes it to become supersaturated and thus super sticky.

    • I’d like to tread carefully because I know Harris has a lot of research experience and I don’t, but when one looks at research holistically (including new papers by i.e. James O’Keefe, who Peter interviewed after this), i.e. population studies (correlations between the introduction of foods/wide consumption/changing rates of diabetes/hypertension/etc), RCT’s showing linoleic acid consumption elevates adipose linoleic acid as well as Lp(a) and oxidized apoB, etc, I think Bill’s advice that seed oils are unharmful is actually irresponsible.

      Furthermore, his arguments in favour were weak — citing solely observational data about serum LA despite Peter mentioning consumption doesn’t correlate with serum levels, the contrary observational evidence that consumption correlates directly with adipose LA and that adipose LA correlates directly with obesity and well with other metabolic syndrome metrics, and he himself cited the Eskimos as a population that ate essentially zero plant derived LA. Data on Japan is also quite interesting, given their (IIRC) increase in LA intake via seed oils has increased 13x since 1958 and their calorie and carb consumption have come way down but their diabetes numbers are not dissimilar to the US’s and their obesity etc is far worse than previously. Easily oxidized seed oils at the sky-high quantities we consume them in haven’t been available to us for very long and they’re exclusively found in processed foods. I don’t think LA requirements are very high and it’s easy to get enough from animal foods and nuts.
      Happy to be wrong, but I haven’t seen good contrary arguments.

      • I was also hoping to hear more about Krill oil, thats what I have always taken since I heard it was better absorbed.. is it worth the premium? Maybe take both?

  4. The very last thing Bill said was not accurate. The reason that Rhonda Patrick used Nordic Naturals brand fish oil was that 1) it was in triglyceride form and not ethyl ester form 2) was nitrogen processing I believe.

    There are in fact several manufacturers of fish oil that put the isolate back in triglyceride form for better absorption.

    I hate that it was the last thing that he said because it cast doubt in my mind as to the reliability of what I just absorbed.

    • Hi Brad,

      I had similar thoughts around that, but then went on to realize that was is available now is thr natural TG form (3 fatty acids on a glycerol backbone).

      What I took out of this was that if I were to supplement with a fish oil OTC product, it probably would be ethyl esters (for the potency, taken with food) not when fasting.


  5. What I’d love to know is: is there a sustainable plant source that mimics that magic EPA/DHA ratio found in fish? (Ie. hemp and chia seeds?)

  6. I would’ve liked to know more about the potency and bioavailability of various omega-3 forms. Is it better to get the phospholipid form, such as found in salmon roe? Do some forms cross the blood-brain barrier better? I’m especially intrigued by the free fatty acid form. Astrazeneca acquired Omthera pharmaceuticals and there might be a combo rosuvastatin-epanova (free fatty acid omega 3) med in the future. Does the free fatty acid form show any promise on lipid metrics in addition to lowering triglycerides?

  7. I like this post, and the secret of long and happy life has been discovered by Ph.D. Allen Omton and Serge Dobrow. They found the hidden in human’s mind internal program that needs to be activated to keep you out of suffer and death.
    John Logger

  8. No mention of connection to prostate cancer and fish oil supplementation.
    You can find it at pubmed.gov

  9. Thank you. Interesting overview and discussion, perhaps not always as nuanced as prior podcasts.

    Much of what we know about fatty acids has changed substantially over the last 20-30 years, so it may not make a lot of sense to make bold statements like there is no such thing as too much omega-3 (for instance, there is no mention of potential risks associated with higher omega-3 intake due to increased lipid peroxidation, higher free radicals, more cell damage, etc. that I’ve read about elsewhere).

    Also, statements on omega-6 were perhaps overly bold (“not as bad as people think”) given how little is known about its impact. I think Attia rightly pushes back on Harris blanket statement on the increased risk for major diseases when the intake of omega-6 is lowered.

    It would have been interesting to discuss potential benefits of GLA (omega-6) supplements (borage oil) in combination with EPA and DHA.

  10. EPA, DHA, and vitamin E (alpha-tocopherol) per 100 grams of:

    Cod liver oil 11 g 12 g 30 mg
    Cod liver, canned 5.4 g 4 g 20 mg
    Salmon 0.6-0.9 g 1.2-1.9 g 2 mg

  11. Just FYI, another great fish oil supplement company is OmegaVia.
    And they do make a 100% EPA product, if that is your goal.

  12. Thanks for the great podcast! One questions that is left open for me and that I am curious about:
    As far as I learned taking both EPA and DHA in supplements is beneficial to mimic the natural composition. But what is the ideal ratio of EPA / DHA in supplements? In most supplements I see a DHA / EPA = 2:1.

    Any ideas?

    • In addition to OmegaVia, there is another pure EPA product available. Pharmepa Restore Pure EPA.

  13. “Conclusions: Advice to substitute polyunsaturated fats for saturated fats is a key component of worldwide dietary guidelines for coronary heart disease risk reduction. However, clinical benefits of the most abundant polyunsaturated fatty acid, omega 6 linoleic acid, have not been established. In this cohort, substituting dietary linoleic acid in place of saturated fats increased the rates of death from all causes, coronary heart disease, and cardiovascular disease. An updated meta-analysis of linoleic acid intervention trials showed no evidence of cardiovascular benefit. These findings could have important implications for worldwide dietary advice to substitute omega 6 linoleic acid, or polyunsaturated fats in general, for saturated fats.”


  14. Peter, as someone trained in biochemistry/molecular biology and with a multi-decade career in the life sciences, I have discovered your podcast just in the last 2 years and am an avid listener. Just finished your great episode with Bill Harris, and he mentioned the AZ STRENGTH trial on Epanova. FYI, AZ just announced the discontinuance of that trial due to lack of benefit:


    Anyways, it feels worthy of a follow-up with Bill or maybe just a quick 10-minute hit with your take. In my mind, perhaps it may also call into question the results of REDUCE-IT/Vascepa, given EPA was also administered in combo with DHA at the same dose, and in a more bioavailable FFA form. Thoughts?

    Michael D.
    Cambridge, MA

  15. Very interesting. Would love to know more about optimal amounts of intake for kids at various ages and whether and how much they should supplement as well. More generally, it would be great if future podcasts about the various health topics (specifically about exercise and nutrition) could include information about if and how this should be applied (or not) to the younger generation.

  16. I know that Peter has recommended Carlson as one brand of omega supplements that his patients have had success with. Has anyone seen any evaluations of Thorne’s Super EPA products?

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