Should you spend your money on Omega-3 fatty acids supplements like fish oil to improve your brain health or delay cognitive decline? Here's what the science says.
Study after study links eating more fish to better brain health — and to lower risk of developing dementia. That’s because fish — in particular, cold-water, fatty fish, like salmon, for example — is rich in omega-3 fatty acids. (Specifically, we’re talking about docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) — important building blocks for cells.)
As a result, many companies now market DHA and EPA as omega-3 fish oil supplements in the nutrients, vitamins and supplements aisle at your local pharmacy, hailing the compounds’ brain-boosting potential. Around 8 percent of Americans take omega-3 supplements daily to boost their brain health.
There is a caveat, however: Although omega-3 fish oils have shown great results in the lab — improving brain health measurably in lab specimens of rats, mice, and brain cells in Petri dishes — the same may not be true for humans. Clinical trials of omega-3 fish oils and of these specific omega-3 fatty acid compounds DHA and EPA have so far failed to show any particular brain benefits for healthy adults, nor for people with Alzheimer’s, dementia, or cognitive decline.
Pieter Cohen, associate professor of medicine at Cambridge Health Alliance, told Being Patient that the observational dietary studies that have shown a light on the potential of omega-3s so far are great for generating ideas — but they don’t show any clear, scientifically verifiable cause and effect. In other words, while studies so far have shown a potential link between omega-3 fatty acids in fish and brain health, there isn’t enough data at this point to say that omega-3 fatty acid supplements will improve human brain health.
“To see if there’s a true health effect, omega-3 fish oil would need to have that effect in carefully conducted clinical trials,” Cohen said. “So far the trial data on omega-3 and prevention of dementia is not promising.”
Does eating fish and other foods high in omega-3 fatty acids lower the risk of Alzheimer’s or dementia?
To figure out how much of these nutrients people are getting from their diet, scientists have used surveys called food frequency questionnaires.For example, this would translate three to five servings of fish per week into measurements of DHA, EPA, and other omega-3 fatty acids. Then, researchers can check to see if people who ate foods with more omega-3 fatty acids were less likely to develop Alzheimer’s or dementia.
This is easier said than done as researchers are still trying to unravel the link
between Alzheimer’s, dementia and diet. Many important variables like socioeconomic status go unmeasured even though they affect how often people can eat fish. Food questionnaires also aren’t a perfect reflection of a person’s diet. As a result, studies looking at links between brain health and a specific food like fish or omega-3 fatty acids can come to different conclusions.
Take for example a pair of studies, one from 2014 and one from 2016 — one linked higher omega-3 consumption to dementia risk, the other did not find a link. Unmeasured variables like genetic risks could explain why some of these studies disagree. Omega-3 fatty acids, DHA, and EPA may provide more of a benefit to people with the Alzheimer’s APOE4 gene.
Can fish oil supplements reduce the chances of Alzheimer’s or dementia?
Using a clinical trial, scientists can test whether people taking fish oil supplements receive any benefits over a placebo group. This approach to studying omega-3 fatty acids side steps many of the pesky issues with observational diet studies. But few clinical trials have pit omega-3 fatty acids, DHA, or EPA supplements against a placebo.
To look for effects across many smaller studies, researchers can use statistics to combine the evidence across these studies. This is important to do because smaller studies might not be powerful enough to spot an effect. Meanwhile, sometimes individual studies might find something by chance that other researchers aren’t able to repeat in their own similar study.
When it comes to omega-3 supplements, clinical trials failed to show that omega-3 fatty acids protect the brain from Alzheimer’s even over the course of five years. Another 2020 study of omega-3 fatty acids concluded that “omega-3 probably has little or no effect on new neurocognitive outcomes or cognitive impairment.”
OK, but what about overall cognitive health and brain function?
Omega-3 fatty acids, especially DHA and EPA are “essential” nutrients. The cells throughout the body and brain do not have the machinery to make EPA or DHA on its own. In the brain, omega-3 fatty acids, DHA, and EPA are crucial for oligodendrocytes to grow and mature. These brain cells form fatty sheaths around neurons to insulate electrical signals. In animal experiments, DHA and EPA help oligodendrocytes regrow their fatty sheaths.
But trials in healthy individuals have shown that omega-3 fatty acids, DHA, and EPA are unlikely to boost brain power. A 2015 analysis looked at 24 trials of omega-3 fish supplements which tested the supplements on healthy people and those with ADHD. Only people with omega-3 fatty acid deficiency showed any cognitive improvement.
Think of the body as a LEGO set. There are many different building blocks that are required to build the LEGO body. Having two or three duplicates of each building block doesn’t really help the LEGO structure. They aren’t required to build the model. They’re just extra.
How much fish and other omega-3 rich foods should I eat?
There is no scientific consensus on how much omega-3 fatty acids should be eaten each day. The American Heart Association recommends two servings of fish per week (around three to four ounces in total) to make sure the body is getting enough omega-3 fatty acids. Eating more fish is also linked to healthier levels of blood pressure, suggesting that omega-3 rich foods may modify one of the major risk factors for Alzheimer’s and other dementias.
Worried about getting enough DHA, EPA, and other fatty acids? Fret not — according to the National Institute of Health, the majority of Americans get enough omega-3 fatty acids through diet alone. Very few Americans develop the characteristic symptoms of a deficiency — rough, scaly skin and a red, swollen, itchy rash.
Should healthy people take omega-3 fatty acid supplements?
Not all omega-3s are good omega-3s, experts warn. Those that come from the vitamins and supplement aisle at your local grocery store or pharmacy will likely not pack the same punch as omega-3 fatty acids in their natural form, via your diet.
“I don’t recommend omega-3 fish supplements to my healthy patients,” Cohen said. “On the other hand, increasing fish consumption is recommended for general health, as this also has the benefit of decreasing meat consumption.”
He added the caveat that raw fish should be avoided during pregnancy.
The big problem with supplements, Cohen explained, is the lack of regulation. Omega-3 fish oil manufacturers don’t need to prove the product works or test its quality. Some manufacturers in the past have made false claims about their omega-3, DHA, EPA, or fish oil supplements.
In 2010 the Federal Trade Commission issued warnings to 11 companies. These companies claimed that their children’s omega-3 fatty acid supplements promoted brain function, vision health, and development. More recently in 2021, two companies settled with the Federal Trade Commission, paying a fine for making false claims that their omega-3 supplements could treat fatty liver disease.