A new study from the University of Southern California challenges the widely held belief that fish oil supplements provide cognitive benefits, particularly in preventing Alzheimer’s disease. Despite the popularity of these supplements, which are used by roughly 19 million American adults — about one in five people over age 60 — the research found no evidence that daily fish oil intake improves brain health or slows cognitive decline.

Fish oil, rich in omega-3 fatty acids such as EPA and DHA, has been promoted for decades as a natural aid to support heart health, reduce inflammation, and enhance brain function. The global market for fish oil currently exceeds $3 billion, reflecting its status as one of the top five dietary supplements in the United States. However, the new findings put these claims under scrutiny.

The study involved 365 participants aged 55 to 80 who reported a dislike for fish but were considered at high risk for Alzheimer’s disease. Over a two-year period, researchers administered daily fish oil supplements to half of the group, while the remainder received placebos. Although the supplements successfully reached the participants’ central nervous system, no significant benefits were observed.

Assessments of cognitive performance—covering memory, attention, and language skills—showed no meaningful differences between those taking fish oil and those receiving placebo. Similarly, imaging studies targeting the hippocampus, a brain region critical for memory formation and one of the earliest areas affected by Alzheimer’s-related tissue loss, revealed no variance in the rate of shrinkage between the two groups.

“We all wish there was a silver bullet for preventing Alzheimer’s, but our findings showed that fish oil supplements do not appear to protect brain health,” said Dr. Hussein Naji Yassine, director of the USC Center for Personalized Brain Health and the study’s lead investigator. He emphasized that while omega-3 fatty acids are important for brain cell function and cognitive connections, supplement consumption alone does not translate into measurable benefits against cognitive decline.

The research underscores that adopting a comprehensive healthy lifestyle remains the most effective approach for maintaining brain health. “Living a healthy lifestyle is the brain’s equivalent of getting regular car maintenance and high-quality oil changes,” Yassine noted, highlighting the importance of overall wellness rather than relying on supplements.

This study provides a critical perspective for consumers considering fish oil supplements specifically for brain health and calls for more rigorous evaluation of widely accepted nutritional interventions in cognitive aging and disease prevention.