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Can High-DHA Fish Oil Help Fight the Flu?
Findings reveal that a fishy omega-3 likely enhances seasonal immunity 02/15/2018 By Craig Weatherby

Myths and misconceptions about seafood-source omega-3 fatty acids abound, unfortunately.

And one of those myths — that omega-3s can suppress your immune response — is both pernicious and erroneous.

Some lab studies in animals find that very large intakes of omega-3s from fish — DHA and EPA — can suppress the response to certain infections.

However, those studies employed extremely high doses relative to the lab animals’ body weights —  equal to a person downing dozens of fish oil capsules daily for several weeks.

And, as scientists say, “the dose makes the poison” — meaning that excessive consumption of anything, including water, is unhealthful.

In contrast, there’s growing evidence that seafood-source omega-3s support the human immune response, and help animals recover from the effects of septic shock.

Now, the results of a clinical study from the University of North Carolina suggest that DHA — one of the two major omega-3s in fish fat — aid the human immune response to infections, including the flu.

Before we examine the new clinical findings, let’s take a quick look at the rodent study that preceded and prompted the recent research in humans.

Omega 3 DHA boosted animals’ immune response to infections
Back in 2013, researchers from the University of North Carolina and Michigan State University reported that in rodents, DHA-rich fish oil enhanced the activity of B-type immune cells.

The researchers divided mice into two groups, and fed them different diets for five weeks:

  • Control diet
  • Same diet, supplemented with DHA-rich fish oil.

The researchers looked for markers of B cell activation, including production of antibodies and cytokines (immune system proteins) — and quickly found those very markers (Gurzell EA et al. 2013).

Based on this finding, the researchers believe that DHA should aid the immune response to infections — including the flu — while moderating the body’s inflammatory response, thereby preventing a counterproductive overreaction.

Those intriguing findings led the Michigan team to conduct their recently published clinical study.

Clinical trial echoes the positive omega-3 findings in animals
The new study was conducted by researchers from East Carolina University, the University of Stirling (UK), the University of Colorado, and the University of North Carolina at Chapel Hill.

They wanted to test the effects of concentrated fish oil, and high-DHA fish oil on B cells — which play several key roles in the immune response to infections:

  • Stimulate antibody production
  • Stimulate production of antimicrobial peptides
  • Present antigens to T cells of the immune system
  • Stimulate production of immune system cytokines

People's flu infections typically start and settle in the respiratory tract, where B cells (and T cells) form the first line of defense.

University of California researchers described the importance of B cells this way (Waffarn EE et al. 2011):

  • “Some B cell subsets provide extensive cross-protection against variants of the ever-mutating virus ...”.
  • “… the rapidly induced, highly protective and long-lived ... humoral response to this virus is contributed by multiple B cell subsets, each generating qualitatively distinct respiratory and systemic responses.”

The university researchers recruited 34 obese men and women and randomly assigned them to one of three groups for the duration of their 12-week trial:

  • Olive oil capsules (control group)
  • Fish oil capsules (high in both EPA and DHA)
  • High-DHA fish oil

Only the participants in the high-DHA group showed enhancements in B cell responses, including higher production of immune-system messenger molecules.

The results suggest that omega-3 DHA enhances a key aspect of immune function, in unique, previously unknown ways (Guesdon W et al. 2017).

The study’s lead author, Raz Shaikh, PhD, put it this way: “Animal studies consistently show that omega-3s robustly improve various aspects of immunity, including inflammation. We were very excited to observe the immune enhancing properties of high-DHA fish oil on B cells in humans.”

As it happens, the same high-DHA pollock fish oil used for this clinical study is used in Vital Choice brand High DHA Brain Care supplements.


  • Baumgarth N, Choi YS, Rothaeusler K, Yang Y, Herzenberg LA. B cell lineage contributions to antiviral host responses. Curr Top Microbiol Immunol. 2008;319:41-61. Review.
  • Fenton JI, Hord NG, Ghosh S, Gurzell EA. Immunomodulation by dietary long chain omega-3 fatty acids and the potential for adverse health outcomes. Prostaglandins Leukot Essent Fatty Acids. 2013 Nov-Dec;89(6):379-90. doi: 10.1016/j.plefa.2013.09.011. Epub 2013 Sep 30. Review.
  • Guesdon W, Kosaraju R, Brophy P, Clark A, Dillingham S, Aziz S, Moyer F, Willson K, Dick JR, Patil SP, Balestrieri N, Armstrong M, Reisdroph N, Shaikh SR. Effects of fish oils on ex vivo B-cell responses of obese subjects upon BCR/TLR stimulation: a pilot study. J Nutr Biochem. 2017 Nov 2;53:72-80. doi: 10.1016/j.jnutbio.2017.10.009. [Epub ahead of print]
  • Hung P, Gu JY, Kaku S, Yunoki S, Ohkura K, Ikeda I, Tachibana H, Sugano M, Yazawa K, Yamada K. Dietary effects of eicosapentaenoic and docosahexaenoic acid esters on lipid metabolism and immune parameters in Sprague-Dawley rats. Biosci Biotechnol Biochem. 2000 Dec;64(12):2588-93.
  • Hung P, Kaku S, Yunoki S, Ohkura K, Gu JY, Ikeda I, Sugano M, Yazawa K, Yamada K. Dietary effect of EPA-rich and DHA-rich fish oils on the immune function of Sprague-Dawley rats. Biosci Biotechnol Biochem. 1999 Jan;63(1):135-40.
  • Jones GJB, Roper RL. The effects of diets enriched in omega-3 polyunsaturated fatty acids on systemic vaccinia virus infection. Sci Rep. 2017 Nov 22;7(1):15999. doi: 10.1038/s41598-017-16098-7.
  • Körner A, Schlegel M, Theurer J, Frohnmeyer H, Adolph M, Heijink M, Giera M, Rosenberger P, Mirakaj V. Resolution of inflammation and sepsis survival are improved by dietary Ω-3 fatty acids. Cell Death Differ. 2018 Feb;25(2):421-431. doi: 10.1038/cdd.2017.177. Epub 2017 Oct 20.
  • Papanikolaou Y, Brooks J, Reider C, Fulgoni VL 3rd. U.S. adults are not meeting recommended levels for fish and omega-3 fatty acid intake: results of an analysis using observational data from NHANES 2003-2008. Nutr J. 2014 Apr 2;13:31. doi: 10.1186/1475-2891-13-31. Erratum in: Nutr J. 2014;13:64.
  • Waffarn EE, Baumgarth N. Protective B cell responses to flu--no fluke! J Immunol. 2011 Apr 1;186(7):3823-9. doi: 10.4049/jimmunol.1002090. Review.

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