There’s a reason fish oil capsules and other omega-3 supplements are so popular. “Omega-3 fatty acids are involved in many different fundamental [brain] processes,” says Simon Dyall, a principal academic and head of nutrition at Bournemouth University in the UK.
Omega-3 polyunsaturated fatty acids—namely EPA and DHA—and their metabolites influence gene expression, oxidative stress, cerebral blood flow, levels of neurotransmitters, and other brain-related processes such as the production of new neurons, Dyall explains. DHA in particular is an essential building block of the brain’s cell membranes. So at a molecular level—like a house without bricks or walls—the brain could not exist without omega-3 fatty acids.
What’s not clear today is whether swallowing a fish oil pill or some other type of omega-3 supplement can improve cognitive function or safeguard brain health.
“We have a lot of evidence that omega-3’s may have favorable effects on the brain, but the evidence on dietary intakes and supplements is inconclusive,” says Aron Barbey, an associate professor and director of the Center for Brain Plasticity at the University of Illinois at Urbana-Champagne.
Barbey’s research has linked high blood levels of omega-3s with improved cognitive function and also with increased volume in certain brain structures. But Barbey says these findings are strictly correlational—meaning they don’t show that consuming omega-3’s in food or supplements produces these benefits. He says he’s yet to conduct the kinds of randomized controlled trials that prove dietary omega-3’s will cause positive changes in the way a person’s brain operates or ages.
Others have conducted those sorts of interventional studies, but the results thus far have been mixed
One two-year study of healthy older adults found taking a daily supplement containing 500 mg of DHA and 200 mg of EPA did not significantly change cognitive function compared to a placebo. Another study, this one among middle-aged adults with low levels of dietary omega-3s, found no brain benefits after 18 weeks of EPA and DHA supplementation.