Fish oil supplements: New study shows they don't prevent cognitive decline in older adults

Fish oil supplements, particularly those high in docosahexaenoic acid (DHA), were thought to enhance cognitive function. However, a recent study conducted at the USC School of Medicine found that while DHA reaches the brain, it does not improve memory or slow cognitive decline in older adults at risk for Alzheimer’s disease.

Study Overview and Findings

The clinical trial involved 365 participants aged between 55 and 80 who rarely consumed fish. Almost half of the participants (47%) had the APOE ε4 allele, a genetic risk factor for late-onset Alzheimer’s. Participants were divided into two groups, with one receiving a daily supplement of 2,000 mg of DHA and the other a placebo for 24 months.

Measurements of DHA levels indicated a 17% increase in the cerebrospinal fluid of the DHA group after six months. Despite this, cognitive tests revealed no significant differences in memory or cognitive performance between the DHA and placebo groups.

Why DHA Supplements Failed to Show Benefits

Researchers propose several reasons for the lack of cognitive improvement despite DHA reaching the brain. One theory involves the enzyme calcium-dependent phospholipase A2 (cPLA2), which may disrupt DHA metabolism, preventing its incorporation into synaptic membranes crucial for cognitive function.

Additionally, many participants had cardiovascular risk factors, including obesity and hypertension, which could have limited the effects of DHA supplementation. The average age of participants was 66, and they exhibited minimal cognitive decline, potentially making it difficult to observe any protective benefits of DHA.

Future Directions and Lifestyle Recommendations

The research team plans to further investigate DHA metabolism in the brain and explore personalized treatment strategies. They emphasize that instead of relying solely on supplements, effective measures to reduce the risk of Alzheimer’s disease include regular physical activity, adequate sleep, and a balanced diet.

According to Hussein Naji Yassine, director of the Personalized Brain Health Center at USC, “While omega-3s play an important role in forming brain cell connections needed for cognition, our results do not support fish oil supplements as a preventive measure against Alzheimer’s.”