Key Takeaway:
- The fish oil supplements study found that these supplements did not improve memory, cognitive function, or prevent brain shrinkage in older adults at risk for Alzheimer’s disease.
- Researchers found that omega-3s reached the brain, with DHA levels increasing by 17%, but this produced no measurable cognitive benefits.
- Scientists say healthy lifestyle habits, including exercise, quality sleep, and a balanced diet, remain the most effective known approach to reducing Alzheimer’s risk.
A new fish oil supplements study from the University of Southern California finds that these supplements do not improve memory, cognitive function, or brain health in older adults at risk for Alzheimer’s disease, even though evidence shows that omega-3 fatty acids from the supplements reach the brain.
Researchers Find No Cognitive Benefits From Omega-3 Supplements
The two-year clinical trial, published Thursday in eBioMedicine, examined whether high-dose omega-3 supplements could help prevent Alzheimer’s-related cognitive decline in older adults considered at elevated risk for the disease.
In the fish oil supplements study, researchers enrolled 365 adults between the ages of 55 and 80 who rarely consumed fish and randomly assigned them to receive either daily fish oil supplements or a placebo. The trial was placebo-controlled and double-blinded, meaning neither the participants nor the researchers knew who was receiving the supplements during the study.
The supplements contained 2,000 milligrams of docosahexaenoic acid, or DHA, an omega-3 fatty acid linked to brain function.
“We all wish there was a silver bullet for preventing Alzheimer’s, but the fish oil supplements study showed that these supplements do not appear to protect brain health,” said Hussein Naji Yassine, director of the USC Center for Personalized Brain Health and the study’s lead investigator.
Yassine said the results do not support using fish oil supplements as a preventive measure against Alzheimer’s disease.
Study Confirms Nutrients Reach The Brain But Show No Impact
Researchers first sought to determine whether DHA from the supplements could cross into the brain.
After six months, measurements of cerebrospinal fluid showed an average 17% increase in DHA levels, indicating that the nutrient successfully reached the brain.
However, the biological change did not translate into measurable cognitive benefits.
Participants in the fish oil supplements study completed memory and cognitive assessments at the start and again after two years, but researchers found no significant differences between those who took the supplements and those who received a placebo.
Brain imaging also showed no reduction in shrinkage of the hippocampus, a region associated with memory and often used as a marker of brain aging and Alzheimer’s risk.
Nearly half of the participants, about 47%, carried the APOE4 gene, the strongest known genetic risk factor for late-onset Alzheimer’s disease.
Scientists Shift Focus To Diet And Healthy Living
Researchers now aim to understand why omega-3 fatty acids can reach the brain without producing measurable improvements in cognitive health.
Based on earlier findings, the team believes omega-3s may be more effective when consumed as part of a Mediterranean-style diet rather than as standalone supplements.
“We’re focused on better understanding how the brain processes omega-3s and whether factors, such as poor health, dietary pattern, genetic risk, and age, may change the brain’s ability to effectively absorb and use omega-3s,” Yassine said.
The study did not examine broader lifestyle interventions, but researchers emphasized that healthy habits remain the strongest known defense against cognitive decline.
“Staying healthy throughout life remains the most powerful tool we have for reducing Alzheimer’s risk, including regular exercise, quality sleep, and a balanced diet,” Yassine said.
The research team included scientists and clinicians from the Keck School of Medicine of USC and Keck Medicine of USC.
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