Sigh … here we go again.
The authors of a new evidence review caution against taking high doses of omega-3 fatty acids routinely.
The authors' shaky assertions relate primarily to long-chain omega-3s (EPA and DHA) from seafood and fish oil, krill oil, and other marine oil supplements.

Specifically, they speculate that “excessive” omega-3 intakes may impair the immune response to infection or exacerbate chronic, inflammatory conditions such as colitis or irritable bowel disease (IBD).

Their claims are based entirely on animal studies involving enormous doses of omega-3 fish oil … for example, a whopping six percent of daily calories.

While animal research forms part of any body of scientific evidence, its direct relevance to humans is always uncertain.
Oddly, they fail to cite any evidence of human immune dysfunction related to high omega-3 intakes ... or to mention a recent review of the clinical evidence, which found that while omega-3 fish oils don't always improve colitis or IBD, they don't worsen them, either (Cabré E et al. 2012)
After alarming people with their claim that “excessive” intake poses potential risks to immune function, they leave them hanging, admitting that they cannot define excessive intake (Fenton JI et al. 2013).
As co-author Dr. Norman Hord said, “Because we lack ... knowledge of who might be at risk ... it isn't possible to determine an upper limit at this time …”. (OSU 2013)

And despite their vague, weakly supported warning, they acknowledge that intakes much higher than the average American's are perfectly safe.

Average U.S. intake is very low
Omega-3 intake in the US is so low that it seems irrelevant to raise concerns over excessive intakes.

According to the most recent and comprehensive official survey of Americans' diets and health status (NHANES), the men aged of 51 or older with the highest daily intakes of omega-3 EPA + DHA (90th percentile) were ingesting just 303mg of these seafood source omega-3s. 

That combined total is just 1/10 of the FDA's recommended daily limit of three grams ... which is based on a very outdated 1989 report.
High omega-3 intakes appear safe
The authors made the risible claim that medical science has “no historical experience with high [omega-3] intakes”.
But many clinical trials have used doses of 2 to 4 grams per day.

And the traditional diets of Native Arctic peoples feature far higher amounts of omega-3s.

For example, native Greenlanders historically averaged 9 to 14 grams of long-chain omega 3s daily … thanks to copious consumption of fish, marine mammals (whales and seals), whale and seal blubber, seal oil, and fish oils.
And the authors of a recent study in Alaska's native Yup'ik people came to this conclusion:
“Increasing [omega-3] EPA and DHA intakes to amounts well above those consumed by the general U.S. population may have strong beneficial effects on chronic disease risk.” (Makhoul Z et al. 2010)

Critically, all of the population studies in Arctic peoples eating traditional, marine-based diets find them very healthful.
So much for the authors' claim that medical science has no historical experience with high omega-3 intakes!
Dr. Hord endorsed the idea that generous amounts of omega-3s, well above the U.S. average intake, are healthful:
“Overall, we support the dietary recommendations from the American Heart Association to eat fish – particularly fatty fish like salmon, mackerel, or sardines – at least two times a week”, and he urged “those at risk of coronary artery disease to talk to their doctor about [omega-3] supplements.” (OSU 2013)

Even if the authors' assertion – that extremely high omega-3 intakes pose immune-function risks – were proven to apply to humans, it would apply to very few people taking extremely high doses from supplements, well in excess of the amounts recommended by official bodies.

Evidence that omega-3 intakes far above average are safe
What do U.S. and world health authorities consider safe and effective intakes? 
  • The American Heart Association (AHA) recommends that medically diagnosed heart disease patients take two-to-four grams of combined omega-3 EPA + DHA (2,000 to 4,000mg) a day, in the form of fish or other marine oils.
  • In 2011, the Norwegian Scientific Committee for Food Safety (VKM) said it was not possible to identify adverse effects from taking up to 6.9 grams of omega-3 EPA and DHA per day.
  • In 2012, the European Food Safety Authority (EFSA) reported that supplemental intakes of omega-3 EPA + DHA combined at doses up to 5 grams per day do not raise safety concerns.
  • The U.S. FDA recommends an upper limit of 3 grams of omega-3 EPA + DHA per day.
 We also recommend reading the following sections of our Omega-3 Facts & Sources page:
  • How much omega-3 EPA and DHA do you need?
  • Safety considerations: doses and contraindications
  • Omega-3 levels in Vital Choice seafood and supplements
  • Official omega-3 intake recommendations, worldwide
Authors' claims appear unpersuasive
As Dr. Hord said, “Our main concern here is the hyper-supplemented individual, who may be taking high-dose omega-3 supplements and eating four to five omega-3-enriched foods per day.” (OSU 2013)
In other words, he's talking about a hypothetical person who consumes much more omega-3 fat than the amounts deemed safe and beneficial by the AHA and EU … yet there's ample evidence that intakes two to four times as high are safe and healthful.
For thousands of years, native Arctic peoples (“Eskimos”) have been consuming what we'd consider huge amounts ... see our sidebar, “High omega-3 intakes appear safe”.
Further, the available population studies show no harm from having omega-3 blood levels far in excess of the average Americans … only heart and other health benefits (Hibbeln JR et al. 2006).

And it's important to note that Americans wouldn't need to consume relatively high doses of omega-3s if they didn't consume far too many omega-6 fats ... see “America's Sickening ‘Omega Imbalance'”.)
 Assertion of immune risk stems from rat research
Three years ago, a team led by Michigan State University's Dr. Jenifer Fenton reported that feeding mice extremely large amounts of omega-3s raised the animals' risk of colitis and immune “alteration” (Woodworth HL et al. 2010).
This prompted Dr. Fenton and her co-authors, including Dr. Hord, to explore the potential adverse health outcomes of excessive consumption of omega-3s, by reviewing the available medical research.
Their evidence review – which overlooked highly relevant research – was also prompted by recent human studies that claimed to show higher risk of advanced prostate cancer and atrial fibrillation in people with relatively high blood levels of omega-3s.
But the prostate study they cite has been almost universally dismissed as flawed and utterly meaningless … see “Fishy Prostate News”.
And with possible exceptions, the available evidence shows that omega-3s generally exert heartbeat-normalizing effect, which explains much of their apparent ability to cut the risk of sudden cardiac death in half ... see “Omega-3s Linked to Healthy Heart Beats” and “Misleading Headlines Distort Meaning of Research on Fish and Heart Rhythms”.
Authors appear ignorant of relevant research
The authors' review somehow missed published studies in which, before rats were infected with disease bacteria, they were fed supplemental omega-3-rich fish oil or omega-6-rich corn oil.
(Dietary omega-6 fats compete for space in our cell membranes, and their effects on the immune system differ markedly from those exerted by omega-3s.)
Those studies showed reduced mortality in infected rats, pigs, and dogs “pre-treated” with omega-3-rich fish oil … even in rats fed plant oils rich in omega-3 ALA, which has much less impact on the immune system.
In addition, test tube studies in cells show that levels of pro-inflammatory messenger proteins in the body – so-called “cytokines” like TNF, IL1 and IL6 – dropped in infected animals fed omega-3 fish oil.
Dr. Fenton's team perceived this effect – which results in dampened of activity by immune system macrophage cells – as negative.
But as prominent omega-3 scientist Doug Bibus, Ph.D. wrote, dampened macrophage activity is “something every surgeon would want for their patient and it's why treatment of sepsis often includes efforts to reduce body levels of TNF” and other pro-inflammatory messenger proteins (e.g., cytokines).
The authors also complain that extreme intakes of omega-3 DHA disrupts the “lipid rafts” in our cell membranes.
As Dr. Bibus explained to us, omega-3 DHA is a major structural and functional component of our cells' lipid rafts … and the DHA content of every cell membrane is controlled by our genes and barely affected by DHA intake (unless intake is very low).
For example, omega-3 DHA constitutes most of the fats in our brains' cell membranes, and 70 percent of the fats in our eyes' retinal cell membranes.

Sadly, the review by Dr. Fenton's team represents pure speculation, and may generate unwarranted fear of a nutrient essential to the body that's also proven to help deter or alleviate cardiovascular diseases and other major conditions. 

  • Baldwin N. Regulatory and Labeling Challenges for Long-Chain Omega 3 Products in the European Union. Nutrition and Health 2013, pp 385-395
  • Cabré E, Mañosa M, Gassull MA. Omega-3 fatty acids and inflammatory bowel diseases - a systematic review. Br J Nutr. 2012 Jun;107 Suppl 2:S240-52. doi: 10.1017/S0007114512001626. Review.
  • Fenton JI et al. Immunomodulation by dietary long chain omega-3 fatty acids and the potential for adverse health outcomes. Prostaglandins Leukotrienes Essential Fatty Acids (2013).
  • Hibbeln JR, Nieminen LR, Blasbalg TL, Riggs JA, Lands WE. Healthy intakes of n-3 and n-6 fatty acids: estimations considering worldwide diversity. Am J Clin Nutr 2006 83: S1483-1493
  • Makhoul Z, Kristal AR, Gulati R, Luick B, Bersamin A, Boyer B, Mohatt GV. Associations of very high intakes of eicosapentaenoic and docosahexaenoic acids with biomarkers of chronic disease risk among Yup'ik Eskimos. Am J Clin Nutr. 2010 Mar;91(3):777-85. doi: 10.3945/ajcn.2009.28820. Epub 2010 Jan 20.
  • Makhoul Z, Kristal AR, Gulati R, Luick B, Bersamin A, O'Brien D, Hopkins SE, Stephensen CB, Stanhope KL, Havel PJ, Boyer B. Associations of obesity with triglycerides and C-reactive protein are attenuated in adults with high red blood cell eicosapentaenoic and docosahexaenoic acids. Eur J Clin Nutr. 2011 Jul;65(7):808-17. doi: 10.1038/ejcn.2011.39. Epub 2011 Mar 23.
  • O'Keefe JH Jr, Harris WS. From Inuit to implementation: omega-3 fatty acids come of age. Mayo Clin Proc. 2000 Jun;75(6):607-14. Review.
  • Oregon State University (OSU). Excess omega-3 fatty acids could lead to negative health effects. October 28, 2013. Accessed at
  • Starling S. GOED issues mixed review of EU's omega-3 labelling plans. NutraIngredients. January 2013. Accessed at
  • Woodworth HL, McCaskey SJ, Duriancik DM, Clinthorne JF, Langohr IM, Gardner EM, Fenton JI. Dietary fish oil alters T lymphocyte cell populations and exacerbates disease in a mouse model of inflammatory colitis. Cancer Res. 2010 Oct 15;70(20):7960-9. doi: 10.1158/0008-5472.CAN-10-1396. Epub 2010 Aug 26.