Why fish stomps flax as a source of omega-3

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  1. Moss Bliss’s avatar

    The studies on mental health benefits all point to EPA, not DHA, as the primary agent.  See also The Omega-3 Connection by Andrew Stoll, M.D., of Harvard Medical School.  Nonetheless, fish oil is the almost-sole direct source of EPA.  Good article.

  2. Chris Kresser’s avatar

    Many studies suggesting EPA provides the greatest benefit are flawed. They are conducted in humans consuming a massive excess of linoleate; they have used very small amounts of ALA; they measure blood levels instead of tissue levels; and they don’t take into account vitamin B6 status or any of the other variables that affect desaturase activity.

    The standard American diet is excessively high in LA (at least fifteen times the required amount). LA depresses the production of DHA, especially if the intake of ALA is low (as it often is in the U.S.) Since DHA, but not EPA, is preferentially incorporated into tissues, measuring blood levels probably overestimates EPA and underestimates DHA.

    The EPA content of terrestrial animal products, even those rich in DHA, is minimal. While DHA content in tissues is very similar across all mammals, the same is not true for EPA.

    For these reasons I believe the role of EPA has been overestimated.

  3. Robert Jacobs’s avatar

    Thanks for a good piece on Omega 3′s.  I agree that fish is healthy, and, if one wants Omega 3′s (I still remain skeptical that this is true), fish is probably the best source.
    It has long been a primary belief of mine that whatever is commonly promoted and sold to consumers is probably not healthy, or that the kernel of truth regarding the issue is seriously misunderstood.  That makes me a skeptic of nearly everything.  However, from my previous readings (these are sources cited by others, not me, I am just a layman trying to figure things out) some research seems to have doubts about DHA and all Omega 3′s.  Just thought I send some of their references:

    Free Radic Res. 2001 Apr;34(4): 427-35. DHA supplementation increases oxidative damage in bone marrow DNA in rats and the relation to antioxidant vitamins. Umegaki, et al.
    J Physiol. Feb 15;475(1):83-93. Facilitatory effect of DHA on N-methyl-d-aspartate response in pyramidal neurons of rats’ cerebral cortex. Nishikawa, et al.
    [ I think this entire piece is worth a read ] : http://raypeat.com/articles/articles/fishoil.shtml

    Am J Clin Nutr. 2004 Nov;80(5):1167-74. Docosahexaenoic acid concentrations are higher in women than in men because of estrogenic effects. Giltay EJ, Gooren LJ, Toorians AW, Katan MB, Zock PL. “The proportion of DHA was 15 +/- 4% (x +/- SEM; P < 0.0005) higher in the women than in the men. Among the women, those taking oral contraceptives had 10 +/- 4% (P = 0.08) higher DHA concentrations than did those not taking oral contraceptives. Administration of oral ethinyl estradiol, but not transdermal 17beta-estradiol, increased DHA by 42 +/- 8% (P < 0.0005), whereas the antiandrogen cyproterone acetate did not affect DHA. Parenteral testosterone decreased DHA by 22 +/- 4% (P < 0.0005) in female-to-male transsexual subjects. Anastrozole decreased estradiol concentrations significantly and DHA concentrations nonsignificantly (9 +/- 6%; P = 0.09). CONCLUSION: Estrogens cause higher DHA concentrations in women than in men, probably by upregulating synthesis of DHA from vegetable precursors.
    Neurobiol Aging. 1982 Fall;3(3):173-8. Lipid peroxides in brain during aging and vitamin E deficiency: possible relations to changes in neurotransmitter indices. Noda Y, McGeer PL, McGeer EG. “Lipid peroxide levels, were found to be significantly higher in brains of 18 month old as compared to 4 month old rats, with particularly large increases occurring in the olfactory bulb, globus pallidus, cerebral cortex and caudate-putamen (CP). Eighteen month old rats fed a vitamin E deficient diet for 9 months before sacrifice had lipid peroxide levels significantly higher than age-matched controls in the cerebral cortex, hippocampus and hypothalamus.” “Age-related decreases were seen in choline acetyltransferase, acetylcholinesterase and 3H-QNB binding in some but not all brain regions, while GABA transaminase and MAO showed age-related increases.” “As compared with controls, vitamin E deficient rats showed decreases of 38% in cortical 3H-DHA binding, of 33% in 3H-QNB binding in the CP and of 23% and 12% in choline acetyltransferase in the CP and cerebellum, respectively.”

    Naunyn Schmiedebergs Arch Pharmacol. 2005 Mar;371(3):202-11. Epub 2005 Apr 15. Antiarrhythmic and electrophysiological effects of long-chain omega-3 polyunsaturated fatty acids. Dhein S, Michaelis B, Mohr FW. “Atrioventricular conduction time was slowed only by DHA and EPA.” “Regarding antiarrhythmic activity we found that the threshold for elicitation of a ventricular extrasystole was concentration-dependently enhanced by DHA and EPA, but not by ALA. DHA dose-dependently reduced longitudinal propagation velocity V(L) and to a lower extent transverse velocity V(T).”
    J Biol Chem. 2002 Oct 18;277(42):39368-78. The mechanism of docosahexaenoic acid-induced phospholipase D activation inhuman lymphocytes involves exclusion of the enzyme from lipid rafts. Diaz O, Berquand A, Dubois M, Di Agostino S, Sette C, Bourgoin S, Lagarde M, Nemoz G, Prigent AF. “Docosahexaenoic acid (DHA), an n-3 polyunsaturated fatty acid that inhibits T lymphocyte activation, has been shown to stimulate phospholipase D (PLD) activity in stimulated human peripheral blood mononuclear cells (PBMC).” “This PLD activation might be responsible for the immunosuppressive effect of DHA because it is known to transmit antiproliferative signals in lymphoid cells.”
    J Nutr 2000 Dec;130(12):3028-33. Polyunsaturated (n-3) fatty acids susceptible to peroxidation are increased in plasma and tissue lipids of rats fed docosahexaenoic acid-containing oils. Song JH, Fujimoto K, Miyazawa T.. “Thus, high incorporation of (n-3) fatty acids (mainly DHA) into plasma and tissue lipids due to DHA-containing oil ingestion may undesirably affect tissues by enhancing susceptibility of membranes to lipid peroxidation and by disrupting the antioxidant system.”

  4. Risa Graves’s avatar

    Could you please comment as to the amount of fish, and what types we should be consuming? Salmon and sardines are my favorites, but are there others high in omega 3′s? thank you

  5. Chris Kresser’s avatar


    I’ve read a lot of Ray Peat’s stuff, as well as other research suggesting n-3s aren’t essential. Overall, I believe the epidemiological and clinical evidence supports the hypothesis that DHA reduces CVD mortality and improves other outcomes. I’ll be covering this in more detail in subsequent posts in this series.

  6. Chris Kresser’s avatar


    I’ll be answering your questions in detail in subsequent posts in this series.

  7. Robert Jacobs’s avatar

    Chris   –
    Right. I know you have done so, by the comments you have made and your writings.  I look forward to your next piece.  Keep up the good work.

  8. Moss Bliss’s avatar

    @Chris Kesser – EPA content in the body could easily be overestimated, but brain content is quite high.  Dr. Stoll’s tests, and others, show that DHA has less effect on mental processes, specifically aiding proper firing of neurons, than EPA does.  Almost beside the point – fish oil is better than flax, hemp, etc.
    We could use some studies on GLA.  There are a few positive indications in mental health, but I have yet to see verifiable studies.

  9. Jesse’s avatar

    I’d like to thank you for inspiring me to actually take my algal oil. The capsules are so big that I hadn’t been able to swallow them before tonight. It’s so much more pleasant to swallow them than to break them open and mix them into my oatmeal.
    Also, what exactly does DHA DO? What happens if we don’t get enough?

  10. Chris Kresser’s avatar

    I’ll be covering that in detail in the posts to follow.

  11. enliteneer’s avatar

    Is it true that all polyunsaturated fats have omega-6 and omega-3s?
    Similarly, would all monounsaturated fats contain omega-9s?

  12. Chris Kresser’s avatar

    Not exactly. A polyunsaturated fat is a fatty acid with more than one double-bond. Omega-6 and Omega-3 are different types of polyunsaturated fatty acids. It is true that many foods have a range of fats in them, including polyunsaturated (omega-3 and omega-6), monounsaturated (n-9 and n-7) and saturated. When we refer to a “saturated fat”, like coconut oil, we’re referring to a fat that is primarily made up of saturated fatty acids. Coconut oil is 92.1% saturated fat, 6.2% monounsaturated, and 1.6% polyunsaturated. Most fats have a more even distribution of fatty acids. All monounsaturated fats will contain at least some omega-9.

  13. SN’s avatar

    Our ancestors were never primarily carnivorous. Animal based foods were few and far between until modern humans … and even then animal based foods were few and far between for all but the most wealthy until very recently in our history. When there’s such a glaring mistake, it’s hard to take any of your other “facts” seriously.

  14. Chris Kresser’s avatar


    Show me one study published in a reputable journal that supports your viewpoint. The idea that animal foods were “few and far between” is absurd.

  15. Moss Bliss’s avatar

    Ditto, SN.  Show me your sources.
    The anthropologists who talked with Dr. Stoll for his book indicated that, at some point in our evolution, there were several hominid species competing, and the tribes that lived along the lake (spearing and eating fish) were the ones whose brains grew, enabling them to out-compete the other tribes and causing the final step in Homo sapiens.

  16. Chris Kresser’s avatar


    I agree with you on that.  I’ve seen some interesting evidence which contradicts the “savannah hypothesis”, and suggests instead that hominids evolved along the edges of lakes as Dr. Stoll reports.

    We won’t see any sources from SN.  There aren’t any.

  17. Moss Bliss’s avatar

    @Robert Jacobs – I know that fish oil has been one of the most significant contributors to my remaining relatively mentally healthy without all the psychiatric drugs my doctors had me on a merry-go-round of.  As Dr. Stoll suggests that EPA is the major reason for this, I am thankful.  Note that Dr. Stoll convinced his wife so much of his studies that she started a company producing OmegaBrite, a product with a 10:1 ratio of EPA:DHA, even though Dr. Stoll’s studies said nothing about other than a 3:2 ratio of them.
    @Chris Kresser — Thanks for more articles.  I’m going over there to read them now.

  18. Tracee’s avatar

    I love your series.  Adding omega-3 supplementation while decreasing omega-6 in our diets was our first diet change that my son’s autism made big improvements on (the SCD was the other drastic improvement). For some reason, the research points to autistics doing better with a higher EPA to DHA ratio (the reverse for ADHD). My son is more bright-eyed  with a higher EPA blend. I had also found  a journal article that showed EPA seemed to be protective against LPS. So maybe there’s more to the EPA thing than we can tell?

  19. Chris Kresser’s avatar

    Hi Tracee,

    Thanks for sharing your experience.  Yes, there is still much we don’t know – especially about the relative importance of EPA and DHA.  It’s interesting to hear that EPA is more effective for your son.

  20. Roger Kaza’s avatar

    Hi, great post and podcast.
    I know fish oil stomps flax, but I have two questions:
    Do plant-based n-3 oils “count” in our caloric balancing act of n-3 and n-6, even if 99%  of it doesn’t get converted?
    Is it possible that the unconverted 99% is valuable and healthy in some other way besides simple conversion to DHA and EPA?
    Thanks for your work.

  21. Chris Kresser’s avatar

    N-3 still counts in the ratio, but you’d want to emphasize EPA & DHA. And yes, it’s possible that ALA has some benefit but studies definitely suggest that the bulk of the benefit comes from EPA & DHA.

  22. Khrystyna’s avatar

    Thanks so much for writing this series of articles on fats and fish oils, I recently converted to a paleo diet and eating too many nuts and not enough fish has been my major downfall, this has given me the motivational kick up the arse I needed to get it together and sort it out. I love your site, keep up the great work, it’s very much appreciated!
    Take care,


  23. Khrystyna’s avatar

    Oh and I hope you don’t mind I linked you up to my blog!

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