Trial Finds DHA Supplements Raise Brain Fluid Levels but Show No Effect on Memory Scores or Brain Volume

A two-year randomized trial at the USC School of Medicine found that daily 2,000 mg DHA supplements raised cerebrospinal fluid concentrations by 17 percent but produced no significant differences in cognitive scores or hippocampal volume compared with placebo.

Wired reported the findings from the study of 365 adults aged 55 to 80 who consumed less than 200 mg of DHA daily from food. Participants were assigned to either the DHA group or a placebo of corn and soybean oil indistinguishable in appearance, taste, and smell.

Forty-seven percent carried the APOE ε4 allele. After six months, DHA levels rose equally in carriers and non-carriers. After 24 months, scores on the Repeatable Battery for the Assessment of Neuropsychological Status showed no group differences, and changes in hippocampal volume were also equivalent.

He added that while omega-3s support brain cell connections, the results do not support fish oil supplements as a preventive measure against Alzheimer’s. The average participant age was 66. Thirty-eight percent of enrollees dropped out before completion, partly during the Covid-19 pandemic, and the study was conducted at a single center.

Researchers noted possible explanations including enzyme activity that may break down DHA before it reaches synaptic membranes and the presence of cardiovascular risk factors in many participants. The team plans further work on DHA metabolism, studies in people with preclinical Alzheimer's disease, and use of additional biomarkers such as plasma phosphorylated tau.

The findings suggest established lifestyle measures remain the primary approach to lowering Alzheimer's risk.