Fish Oil Fails to Improve Memory in At Risk Seniors

Docosahexaenoic acid (DHA), an omega-3 fatty acid found in fish and fish oil supplements was thought to protect against Alzheimer's disease and other forms of dementia. A new clinical trial suggests that high dose supplements of omega 3 do not. Even though the DHA successfully penetrated the brain, no improvement in memory, thinking skills, or brain structure was seen in over two years of monitoring.

The study included 365 adults ages 55 to 80 who did not have dementia but had at least one risk factor for dementia, such as obesity, high blood pressure, high cholesterol, or physical inactivity. Participants also had low dietary intake of DHA, making them an ideal group to test whether supplementation could provide benefits. Nearly half carried an APOE gene, a strong genetic risk factor for Alzheimer's disease.

Participants were randomly assigned to receive either 2 grams of DHA daily or a placebo for 24 months. 

DHA levels in their cerebrospinal fluid (the liquid that surrounds the brain and spinal cord) were measured. After six months, people taking DHA showed a significant increase in a marker of brain DHA exposure. The increase occurred regardless of whether participants carried the APOE gene. 

No Improvement in Memory or Brain Structure

Despite the detectable increase in brain DHA levels, participants did not experience measurable cognitive benefits.

Researchers evaluated memory, attention, language, and other thinking abilities throughout the study. After two years, cognitive scores improved slightly in both the DHA and placebo groups, but there was no meaningful difference between them.

Brain imaging results told a similar story.

The researchers found no evidence that DHA slowed shrinkage of the hippocampus, a brain region critical for memory that is often affected early in Alzheimer's disease. Measures of cortical thickness and other structural brain changes also showed no benefit from supplementation.

Previous omega-3 studies often failed to show cognitive benefits, but researchers could not determine whether the problem was that DHA never reached the brain or whether increasing brain DHA simply was not enough to affect cognition. This study demonstrates that any lack of cognitive improvement cannot be blamed on poor delivery to the brain.

Nothing in the study indicates that DHA is harmful. The supplement was generally safe, and adverse events were similar in the DHA and placebo groups.

Omega-3s play an important role in forming brain cell connections needed for cognition, but these findings indicate that simply raising DHA levels in the brain may not be enough to prevent cognitive decline in otherwise healthy older adults at risk for dementia.

Managing Lifestyle for Brain Health

The study findings also suggest that Alzheimer's disease and cognitive decline may involve biological processes that cannot be addressed by a single nutrient alone.

Many participants had cardiovascular and metabolic risk factors, conditions that can promote inflammation and negatively affect brain health.

Lead author Hussein Naji Yassine, MD, director of the USC Center for Personalized Brain Health said, "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."

Personalized approaches that manage conditions known to cause or accelerate cognitive decline are important.

“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,” said Yassine. 

“Living a healthy lifestyle is the brain’s equivalent of getting regular car maintenance and high-quality oil changes. The brain is more likely to lose greater function if health issues in other parts of the body go unaddressed, in the same way that car engines stop working if regular maintenance is skipped.”