Fish oil got into the brain. The memory scores stayed where they were.
That is the short version of a two-year trial run by Keck Medicine of USC and published in eBioMedicine. It tested high-dose DHA, an omega-3 fatty acid tied to brain function, in 365 adults aged 55 to 80. Every participant rarely ate fish and was considered at elevated risk of Alzheimer’s disease. Nearly half, 47 percent, carried the APOE4 gene, the strongest known genetic risk factor for late-onset Alzheimer’s.
Volunteers were randomly assigned to a daily capsule holding 2,000 mg of DHA or to a placebo. The design was double-blinded.
Proof the nutrient arrived
Before asking whether the supplement helped, the team asked whether it got there at all. They sampled cerebrospinal fluid, the liquid that surrounds the brain and spinal cord. After six months, DHA levels had gone up by an average of 17 percent.
Then came the tests. Researchers assessed memory and thinking at the start and again two years later. People who took DHA scored no better than people who took the placebo. Scans of the hippocampus, a memory region that doctors use as a marker of brain aging and Alzheimer’s risk, showed the supplement did not slow its shrinkage.
“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 Hussein Naji Yassine, MD, director of the USC Center for Personalized Brain Health and lead investigator. He added: “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.”
Money and what comes next
Americans spend more than $1 billion a year on fish oil supplements, mostly because of claims about brain health.
Yassine and his colleagues now want to know why the omega-3s reach the brain without changing how it performs. Earlier research leads them to suspect the nutrients work better inside a Mediterranean-style diet than as a stand-alone pill. That diet is naturally rich in omega-3s and has been linked to a lower risk of Alzheimer’s. The group is also working on medications that might help the brain make better use of these nutrients.
Lifestyle was outside the scope of the trial, but Yassine was direct about it. “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,” he said. Anyone weighing supplements should check with a doctor first.
