Fish Oil Supplements Failed to Prevent or Slow Cognitive Decline in Trial
A placebo-controlled trial put fish oil supplements to the test. Over two years, the supplements failed to slow cognitive decline in healthy older adults.
Over one in five Americans over 60 take omega-3 fatty acid supplements because of their potential protective effects on the brain and heart.
People who eat less fish, which are naturally high in these healthy fats, or have lower levels of omega-3 fatty acids, like docosahexaenoic acid (DHA), have an increased risk of dementia and cognitive decline. In addition, omega-3 fatty acids are a foundational building block of brain cells, and important players in neuronal communication — leading many to turn to supplements for their potential neuroprotective abilities.
Dr. Hussein Naji Yassine, endocrinologist and director of the USC Center for Personalized Brain Health, began formulating a study about a decade ago to rigorously test the idea. It took several years to recruit enough people who ate very little fish in their diet, as well as carriers of the ApoE4 Alzheimer’s risk gene who have altered fat metabolism and may need a higher omega-3 intake. Yassine’s team tested a high-dose DHA supplement in this population to see if it would slow cognitive decline over two years.
The study, published in eBioMedicine, showed that the supplement reached the brain and substantially increased the levels of omega-3s yet failed to improve cognition or biomarkers of Alzheimer’s, even among ApoE4 carriers. “The takeaway isn’t that omega-3 is not important,” said Yassine, “But taking it as a supplement, not sufficient.”
Omega-3 supplements on trial
Yassine and his team recruited 365 participants aged 55 to 80 who ate very little fish, were cognitively healthy at baseline, and had at least one Alzheimer’s risk factor. Half of the participants were randomly assigned to receive a placebo each day while the other half received two grams per day of DHA.
After six months, the researchers sampled the cerebrospinal fluid and saw an increase in the levels of DHA, indicating that the omega-3 supplement was reaching the brain. But after two years, there was no difference between the placebo and DHA group on cognitive tests.
DHA did not slow the shrinkage of the brain’s memory hub, the hippocampus, another biomarker of Alzheimer’s. Individuals who carried one copy of the ApoE4 gene did not show any added cognitive benefit.
Dr. Parichita Choudhury, a neurologist at Banner Health who wasn’t involved in the research, told Being Patient that one of the most important conclusions of the study was that carrying a copy of the ApoE4 gene didn’t mean you benefited more from supplementation.
Dr. Pieter Cohen, physician and associate professor at Harvard Medical School, who wasn’t involved in the research, said that the trial provides “further scientific and clinical evidence that omega-3 supplementation has no proven benefit on treating or preventing dementia. Let’s move on from recommending omega three supplementation for memory.”
The future of omega-3 research
Despite the negative data for this study, scientists think omega-3s play an important role in brain health.
“Omega-3 should be part of a healthy lifestyle,” said Yassine. Combining omega-3s, exercise, better sleep, and a higher fiber intake would work better than simply taking a supplement on its own. Yassine emphasized that the supplements are not a “quick fix.”
His team is studying the proteins that break down omega-3 fatty acids to better understand how they’re metabolized in the brain and design drugs that could prolong the effects of these fats. In January, Yassine and his colleagues published a study identifying potential drugs that could block the protein that depletes omega-3s that they validated in cells and mice.
Such treatments would hypothetically prolong the neuroprotective effects of omega-3s and reduce inflammation, which could slow Alzheimer’s-related changes in the brain. But the development is still early and hasn’t reached human testing yet.
Future drugs targeting this pathway would work upstream of the beta-amyloid plaques and tangles that serve as the protein hallmarks of Alzheimer’s.
Still, many people ask their doctors about omega-3 supplements for the brain. In her practice, Choudhury tells them that, “it is more important for you to focus on things that actually have evidence like physical activity, cognitive training, and Mediterranean diet.”
FAQs
The latest randomized-placebo controlled trial found that although high dose omega-3 supplements get to the brain, they fail to slow cognitive decline in individuals at risk of dementia. Even those carrying a copy of the ApoE4 gene failed to benefit over two years.
The latest research found that omega-3 supplements did not slow decline in at-risk older adults. There is no rigorous evidence that omega-3 supplements provide a benefit for those already affected by memory loss.
Omega-3 supplementation alone has failed to move the needle in studies. However, research suggests that the Mediterranean diet especially coupled with exercise, cognitive training, and other interventions may provide protection from the brain and heart.
