On Nutrition

As we age, concerns about developing chronic health conditions such as Type 2 diabetes, heart disease and cancer increase. Interest in preventing or delaying Alzheimer’s disease, dementia and other forms of cognitive decline is also strong, fueling a number of brain health claims about certain foods, nutrients and supplements. For example, many people take omega-3 fatty acids in supplement form hoping it will help them stay mentally sharp. But does the research match the hype?

It’s well documented that omega-3s — especially docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), the types found in fish and seafood — are critical for prenatal and early childhood brain development, in part because the brain contains a high level of omega-3s. But what might this mean for adult brains? Much of the focus on omega-3s and adult health has centered on heart health, and what’s good for the heart may be good for the brain — after all, stroke is one type of cardiovascular disease. But research on omega-3s and cognitive health is less robust.

On a positive note, a 2020 paper that drew data from the 2011-2014 National Health and Nutrition Examination Survey (NHANES) found that higher omega-3 intake was associated with better cognitive performance in adults over age 60, but the authors gave a big caveat: While this association is biologically plausible, it needs to be confirmed by well-designed, long-term studies.

A 2020 systematic review and meta-analysis (a study of studies) from the World Health Organization yielded results suggesting that omega-3s have little or no effect on preventing cognitive impairment. The authors concluded that taking omega-3 supplements for cognitive health is neither helpful nor harmful.

Setting omega-3 supplements aside, what might regularly eating actual fish mean for the brain? It’s well known that Americans don’t eat the recommended amount of fish and seafood, including the types of fatty fish — such as salmon and sardines — that are high in omega-3s. So what can we learn from countries where people do eat more fish?

A 2018 Finnish study of 2,612 middle- and older-aged adults found no consistent association between fatty fish consumption and cognitive decline, but did find that higher omega-3 intake — especially intake of alpha-linolenic acid (ALA) plant-based omega-3s found in walnuts, flaxseeds and chia seeds — was associated with a slower decline in overall cognitive function. Now here’s the kicker: Higher intake of DHA and EPA only appeared to prevent cognitive decline in subjects with a specific genotype (APOE e4) that’s linked to an increased risk of developing late-onset Alzheimer’s disease (after age 65) and a particular form of dementia.

A 2016 Rush University study found a similar connection with that genotype. Among participants in the Rush Memory and Aging Project (MAP), eating fish once per week was associated with slower rates of decline in the ability to remember facts and the ability to quickly process new information (which is important when, say, driving). However, only APOE e4 carriers showed slower rates of decline in these and other types of cognition with weekly seafood consumption. It’s this type of gene-food interaction that could explain inconsistent results in many omega-3 studies.

There are clear benefits to eating the recommended 8 to 12 ounces of fish and seafood per week, even if the scientific jury is still out on its benefits for cognitive health in adults. Fish and seafood are healthy — and heart healthy — sources of protein. As for omega-3 supplements, for now this may be a matter of personal choice, with the understanding that they may not offer all the benefits you desire.