Omega-3 supplements, widely used by older adults to protect brain function, may actually accelerate cognitive decline in those with a genetic risk for Alzheimer's, according to a new study from researchers at the Army Medical University in China.
Analyzing data from over 800 participants in the Alzheimer's Disease Neuroimaging Initiative, the team found that individuals carrying the APOE ε4 gene who took omega-3 showed faster cognitive decline on standard memory and language tests compared to those who did not.
Interestingly, this decline was not linked to classic Alzheimer's biomarkers like brain plaques or tangles, but rather to changes in neuronal synaptic function. The authors caution that their findings are observational and do not prove causation, but they challenge the prevailing view of omega-3 as uniformly beneficial.
They suspect there may be a 'sweet spot' for omega-3 intake, noting that a 2025 systematic review found high doses above 1,500 mg a day could reverse cognitive benefits. The call is for more nuanced research before recommending omega-3 supplements for brain health.