Millions of Americans take fish oil hoping to protect their memory. A two-year randomized trial from the University of Southern California found that a high daily dose of one key omega-3, DHA, did not improve memory or thinking in older adults at higher risk of Alzheimer’s disease. It also did not stop a brain region tied to memory from shrinking.
What the Researchers Did
The trial enrolled 365 adults ages 55 to 80 who rarely ate fish and had an elevated risk of Alzheimer’s. About 47% carried APOE4, a gene variant linked to higher risk. Participants were randomly assigned, double-blind, to take either 2,000 milligrams of DHA a day or a placebo for two years.
The team measured DHA in spinal fluid after six months, tested memory and other thinking skills at the start and end, and used brain imaging to track the size of the hippocampus, a region central to memory.
What They Found
- DHA in spinal fluid rose by an average of 17% in the supplement group, so the omega-3 did reach the brain.
- Memory and thinking scores did not differ from the placebo group after two years.
- The supplement did not prevent hippocampal shrinkage.
The study was led by Hussein Yassine of the USC Center for Personalized Brain Health and was published in eBioMedicine. The National Institutes of Health provided most of the funding.
The Catch
This is one trial of one product, so it is not the last word on omega-3s. A few limits matter when you read the headline:
- It tested high-dose DHA alone, not fish itself or a different supplement mix.
- Participants were older, rarely ate fish and were at elevated risk, so the results may not apply to everyone.
- Exercise, sleep and overall diet were not tested. The researchers suspect that dietary pattern and general health may affect how well the brain uses omega-3s, but the trial did not examine that.
- The results do not show that omega-3s or eating fish are unnecessary.
What to Take From It
Getting a nutrient into the brain is not the same as getting a benefit from it. In this trial, higher DHA levels in spinal fluid did not translate into better memory. If you are considering a supplement for brain health, this is a reason to be skeptical of the promise, and a good topic to raise with your doctor or pharmacist, who know your medications and history.
For more on how small studies can be read too broadly, see our look at a lab study on sweeteners and gut bacteria.
This article is for general information, not medical advice.
More on Contoh
- Lab Study Finds Many Low-Calorie Sweeteners Alter Gut Bacteria. Here’s the Fine Print
- Just 10 Minutes of Daily Exercise Was Linked to Deeper Sleep in a Study of Young Adults
- Late-Night Eating Linked to Higher Risk of Fatty Liver Disease and Cirrhosis in a Study of 199,000 Adults