A new study found that people taking omega-3 supplements showed faster cognitive decline than non-users across multiple standard tests of memory and thinking.
The decline was observed in measures such as MMSE, ADAS-Cog13, and CDR-SB, indicating worsening global cognition, memory, and functional abilities over time.
Researchers concluded that omega-3 supplementation may be linked to accelerated brain metabolic dysfunction (reduced glucose use in key brain regions) rather than classic Alzheimer’s markers like amyloid or tau.
Millions of Americans take daily omega-3 supplements for any number of health reasons. However, a new study is challenging the widespread belief that omega-3 supplements help protect brain health as people age.
Researchers reporting in the Journal of Prevention of Alzheimer’s Disease found that older adults who took omega-3 supplements experienced faster cognitive decline than people who did not use the supplements. However, the study authors cautioned that the findings do not prove the supplements directly caused the decline.
The research tracked participants enrolled in the Alzheimer’s Disease Neuroimaging Initiative (ADNI), a long-running study that monitors cognitive performance and brain changes in older adults over time.
Researchers compared supplement use with results from several commonly used cognitive assessments, including the Mini-Mental State Examination (MMSE), ADAS-Cog13 and the Clinical Dementia Rating Scale-Sum of Boxes (CDR-SB).
Participants taking omega-3 supplements showed steeper declines across multiple measures of memory, thinking and daily functioning compared with non-users.
Brain metabolism may play a role
The study found that the decline was associated less with traditional Alzheimer’s disease markers — such as amyloid plaques or tau tangles — and more with reduced metabolic activity in brain regions linked to cognition.
Brain imaging scans revealed evidence of FDG hypometabolism, meaning lower glucose use in key areas of the brain. Researchers said this reduced metabolic activity may represent a different pathway contributing to cognitive deterioration.
The findings surprised researchers because omega-3 fatty acids, commonly found in fish oil supplements, have long been promoted for potential heart and brain health benefits.
Researchers urge caution, not panic
The authors stressed that the study establishes only an association, not cause and effect.
They said the results should not be interpreted as proof that omega-3 supplements are harmful for everyone, but rather as evidence that the relationship between supplements and brain health may be more complex than previously believed.
The researchers also noted that some people could potentially benefit from omega-3 supplementation while others may not.
Health experts say consumers should avoid making abrupt changes to supplement routines based solely on a single study.
People should discuss any decisions about starting or stopping supplements with their healthcare provider.
Omega-3 supplements remain widely used in the United States for a variety of health reasons, including cardiovascular support, inflammation reduction and general wellness. However, the new findings are likely to fuel additional research into how these supplements affect aging brains over time.