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by Sonya Collins
Updated September 28, 2022
People who eat a lot of seafood, particularly so-called “fatty” fish, may be at lower risk for the loss of thinking skills that can lead to Alzheimer’s disease. That’s why, in 2017, the Global Council on Brain Health put fish on its list of encouraged foods and recommended that people eat at least one serving of non-fried fish per week for better brain health.
“Most studies show that the equivalent of a Mediterranean diet may prevent cognitive decline,” says geriatrician and neuroscientist Howard Fillit, a member of the council and founding executive director and chief scientific officer of the Alzheimer’s Drug Discovery Foundation. “Fruits and vegetables are important, as are oily fish, like salmon, that provide omega-3 fatty acids.”
Researchers speculate that it’s the omega-3s found in fish oil that serve up the brain benefits, but they don’t know for sure.
What are omega-3 fatty acids? First, your body doesn’t produce them. You have to get them from the food you eat. They’re in salmon and mackerel; nuts and seeds; plant-derived oils like canola; and processed foods that are enriched with the nutrient.
In your body, omega-3s are an important part of the membrane around the exterior of every cell in your body. They give your body energy and also have roles to play in your heart, blood vessels, lungs, immune system, and the glands that produce hormones. There are three main types omega-3s: alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). DHA, for example, is found in large quantities in the eyes, sperm cells and the brain.
Because of DHA’s presence in the brain as well as the possible role of seafood in brain health, researchers have tried to determine whether omega-3 supplements might improve or protect brain health. The Global Council on Brain Health, an independent collaborative of scientists, health care providers and other experts, evaluated evidence on the subject in its report. “There’s not enough evidence to recommend taking [omega-3 supplements] for brain health,” says Francine Grodstein, a member of the council. That’s not to say, she adds, “that there is definitive evidence that fish oil supplements don’t work.” Grodstein is a professor of epidemiology at Harvard T.H. Chan School of Public Health.
In fact, a few small studies have found that DHA supplements may help people who have begun to lose some thinking skills. That’s called mild cognitive impairment, and it can, but does not always, lead to Alzheimer’s disease. Some research also shows that people who have low levels of DHA might benefit from supplements. But low DHA is extremely rare in the United States. Research that includes people with a rare omega-3 deficiency doesn’t necessarily apply to the population at large.
“The weight of existing evidence,” the council’s report concludes, “does not sufficiently demonstrate benefit [of supplements] … If you can’t or don’t eat fish, ask your health care provider whether you should take a supplement containing DHA and EPA.”
• “Brain Food: GCBH Recommendations on Nourishing Your Brain Health,” Global Council on Brain Health, 2017. This report summarizes the consensus of the GCBH on the impact of diet on the brain health of adults ages 50 and older. The group concluded that eating fish benefits mental function, possibly due to its omega-3 fatty acid content. However, it acknowledged that some fish may be high in mercury, which is harmful to the brain. Read about and download the full report.
• “Mediterranean Diet and Age-Related Cognitive Decline: A Randomized Clinical Trial,” JAMA Internal Medicine, July 2015. For this study, researchers looked at a sample of 447 people, ages 55 to 80, who were part of the larger PREDIMED study investigating the Mediterranean diet for cardiovascular disease prevention. All of them had cardiovascular risks like smoking, high blood pressure, high cholesterol, and overweight or obesity. Participants were divided into three groups and randomly assigned to eat a Mediterranean diet supplemented with extra-virgin olive oil, a Mediterranean diet supplemented with mixed nuts, or a low-fat diet. People who ate a Mediterranean diet with olive oil or nuts scored higher on tests of mental function than those who ate a low-fat diet. Read the full study.