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Eating fish is associated with an increase in brain volume, but it is apparently not because of its omega-3 content, a new study has found.

Researchers analyzed data from 260 cognitively normal people, average age 78, who had answered diet questionnaires. They’d also had their blood levels of omega-3 fatty acids measured and their brains scanned.

The researchers found that weekly consumption of baked or broiled fish — but not fried fish — was associated with larger gray matter volumes in areas of the brain responsible for memory and cognition, including areas where amyloid plaques, a sign of Alzheimer’s disease, first appear. The association persisted after controlling for age, sex, race, education, physical activity, body mass index and any tissue damage found on the initial magnetic resonance imaging scan of the brain.

The results were the same regardless of omega-3 levels, suggesting that omega-3s were not the determining factor. The study appears in The American Journal of Preventive Medicine.

The lead author, Dr. Cyrus A. Raji, a radiology resident at the Ronald Reagan U.C.L.A. Medical Center, said that eating fish once a week — there was no additional benefit in eating more — and living a generally healthy lifestyle were enough.

“Physical activity, weight control, and so on — these factors influence the brain more than any supplement or any medicine. It’s much more in our control than we thought.”

Related: Broiled Fish With Chermoula

