Population studies have shown that people who report eating more Omega-3 fatty acids (in the form of fatty fish) seem to have a lower risk of developing dementia. Because of this, scientists have hypothesized that fish oil supplements (or supplements containing DHA, an Omega-3 fatty acid found in fish oil and algae) could be used to treat Alzheimer’s. So far, evidence from clinical trials doesn’t support that hypothesis, at least not much.
“The data to date does not support the use of DHA in patients with established Alzheimer’s disease,” says Dr. Joseph Quinn, Associate Professor of Neurology at Oregon Health & Science University. Dr. Quinn led the recent Alzheimer’s Disease Cooperative Study trial which showed no benefit of DHA for people with mild to moderate Alzheimer’s. A large Swedish trial also found no benefit to fish oil supplements for people with mild to moderate Alzheimer’s, except maybe for a small group of people with very mild Alzheimer’s.
What about fish oil or DHA for mild age-related memory loss or for preventing Alzheimer’s? “The jury is still out on preventive effects,” says Dr. Quinn. Two recent studies were negative:
- In a half year Dutch study, Omega-3 fatty acid supplements did not help memory and thinking in older adults
- Results of a trial in England and Wales show that fish oil supplements in healthy older men and women did not help memory and thinking any more than a placebo. During the two year trial period, scores on cognitive tests remained the same in both the group receiving the fish oil supplements and the placebo group.
- This 24 week trial was sponsored by Martek Biosciences, the company that owns the patent on and markets the DHA supplement used in this trial and in the Alzheimer’s Disease Cooperative Study trial above. Most of the scientists conducting the research are employees of or consultants to Martek.
- The researchers changed the main test used to measure effectiveness in the middle of the trial
- Trial participants taking the supplement improved their scores on some parts of this second test more than those taking placebo, but both groups improved. There were no differences between the groups on self-assessment of memory and daily living skills.
So what’s the bottom line for prevention of Alzheimer's or cognitive decline? “I do not push it, but I also do not discourage the use of fish oil for prevention, as there is not much of a downside and potential for other health benefits,” says Dr. Quinn.
You can read about the evidence for other health benefits of fish oil, and about potential side effects and interactions with medicines and supplements, at the U.S. Government’s MedlinePlus site.