Can Omega-3s Prevent Cognitive Decline?

I read about a study showing that taking omega-3 supplements doesn’t slow cognitive decline in older people. I thought omega-3s were protective. What’s the story?

– September 15, 2016

You’re likely referring to findings from a large National Institutes of Health study reported in 2015. Some background: the study, known as AREDS2, was a follow-up of an earlier one, the Age-Related Eye Disease Study (AREDS) designed to determine if a combination of nutritional supplements could slow development of age-related macular degeneration (AMD), a major cause of vision loss among seniors. The first AREDS study determined that a mix of high-dose antioxidant supplements could help slow the progression of AMD and vision loss.

Next, to see if the formula could also help protect brain health, the investigators tested the same antioxidants by dividing the participants into 4 groups and giving each a variation of the formula as follows: (1) the basic AREDS supplement containing vitamins C and E, beta-carotene, zinc and copper; (2) adding omega-3s; (3) adding lutein and zeaxanthin; (4) adding omega-3s plus lutein and zeaxanthin. The nearly 4,000 participants were all considered at high risk of progressing to late-stage AMD. Most (58 percent) were women whose average age was 73. All had cognitive function tests at the study’s start and 2 and 4 years later.

As you know, the researchers reported that adding omega-3s to the AREDS formula didn’t help slow cognitive decline in the participants. I discussed those findings with Jeffrey Blumberg, Ph.D., senior scientist at the Antioxidants Research Laboratory at Tufts University’s Jean Mayer USDA Human Nutrition Research Center on Aging and a professor at Tufts’ Friedman School of Nutrition Science and Policy. He noted that a systematic review and meta-analysis of 15 randomized clinical trials also published in 2015 found significant improvements in some measures of memory among adults with mild memory complaints who took both long-chain omega-3 fatty acids (EPA AND DHA) or DHA alone.

He also pointed out that the dose of omega-3s in AREDS2 was lower than that used in the other studies and was combined with the AREDS supplement containing vitamins and minerals that have been shown to have an influence on cognitive decline and the risk of central neurodegenerative disease.

Dr. Blumberg said other investigators who reviewed AREDS2 saw significant improvements in some measures of cognitive function among the participants. Those positive results were masked, however, by the overall composite summary score showing no benefits. Another possibility: AREDS2 may have tested the supplement too briefly and too late in the aging process, given the average age of the participants.

Other reviewers took issue with aspects of the study’s methods, including the fact that “some very complex aspects of cognitive function were tested, on average, in just a few minutes over the telephone,” unlike traditional cognitive testing, which “is designed to be relatively exhaustive.” Another problem Dr. Blumberg and others have pointed out: AREDS 2 had no placebo (untreated) group. Considering that the participants all had AMD, it wouldn’t have been ethical to ask some to stop taking the antioxidants shown to slow progression of the disease. However, when testing the effects of omega-3s on cognition, the lack of a placebo group becomes a serious limitation, Dr. Blumberg said.

Given the questions raised about AREDS 2, I wouldn’t consider its findings the last word on whether omega-3s can protect against cognitive decline. There is good evidence that they can. Beyond that, research indicates that omega-3s reduce inflammation and therefore may help lower the risk of heart attack, stroke, several forms of cancer and autoimmune diseases. I continue to recommend getting omega-3s by eating oily, wild, cold-water fish 2-3 times per week. If you use fish oil capsules, take those that provide daily doses of 700 to 1,000 mg of EPA and 200 to 500 mg of DHA.

Andrew Weil, M.D.


Emily Chew et al, “Age-Related Eye Disease Study 2 (AREDS2) Research Group. Effect of Omega-3 Fatty Acids, Lutein/Zeaxanthin, or other Nutrient Supplementation on Cognitive Function: The AREDS2 Randomized Clinical Trial.” JAMA, August 25, 2015, doi:10.1001/jama.2015.9677

Karin Yurko-Mauro et al, “Docosahexaenoic acid and adult memory: a systematic review and meta-analysis.” PLoS One, March 18, 2015, doi: 10.1371/journal.pone.012091

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