How Good Are Fish Oil Supplements? Here’s Your Crash Course

Docosahexaenoic acid (DHA), Omega-3 fatty acids, which are found in large amounts in fatty fish such as mackerel and sardines, are thought to improve cognitive function by supporting the connection between brain cells. However, it has not been well demonstrated that DHA taken as a dietary supplement reaches the brain or provides measurable benefits against it. dementia.

With this in mind, a research team at the USC School of Medicine has published the results of a large two-year clinical trial involving adults at high risk for developmental disorders. Alzheimer’s disease. The study found that although DHA supplements reached the brain, they did not improve memory or cognition, nor did they slow brain aging.

“Everyone is hoping for a silver bullet to prevent Alzheimer’s disease, but we can’t say that fish oil supplements protect brain health,” he said Hussein Naji Yassine, director of the Personalized Brain Health Center at USC. “Although omega-3s play an important role in forming connections between brain cells that are necessary for cognition, our results do not support fish oil supplementation as a protective mechanism against Alzheimer’s.”

DHA Reaches the Brain, But…

Yassine and colleagues conducted a randomized, double-blind, placebo-controlled trial involving 365 men and women between the ages of 55 and 80 who did not eat fish. About half of the participants (47 percent) carried the APOE ε4 allele, which causes late-onset Alzheimer’s disease. All participants consumed less than 200 mg of DHA per day through their diet.

Participants were randomly assigned to one of two groups. One group received a daily supplement containing 2,000 mg of DHA, while the other received a placebo for 24 months. The product contained a mixture of corn oil and soybean oil and was unrecognizable to DHA supplements in terms of appearance, taste, and smell. Neither the participants nor the researchers knew which treatment each person received.

The researchers first wanted to know if DHA actually reached the brain. Measurements of DHA levels in the cerebrospinal fluid, which surrounds the brain and spinal cord, showed a 17 percent increase after six months in the DHA group. There was no difference between carriers and non-carriers of the APOE ε4 allele, providing direct evidence that high doses of DHA supplementation reach the brains of cognitively healthy elderly regardless of APOE ε4.

The results were very different, however, when it came to cognitive function and brain structure. After 24 months, participants completed the Repeated Battery for the Assessment of Neuropsychological Status, a standardized test of memory and cognition. No significant differences were found between the DHA and placebo groups. Likewise, there was no significant difference in changes in hippocampal volume, a brain region important for memory and an early sign of Alzheimer’s disease.

Why Didn’t It Work?

The researchers offered several possible explanations for why DHA reached the brain but failed to produce clinical benefits. One possibility involves an enzyme that interferes with DHA metabolism in the brain. When an enzyme called calcium-dependent phospholipase A2 (cPLA2) is activated, it can break down DHA before it can be incorporated into the synaptic membrane – which DHA is thought to play an important role in helping with cognition.

Another possible explanation is that many of the participants had cardiovascular risk factors such as obesity, high blood pressure, and physical inactivity. Chronic inflammation associated with these conditions can interfere with the effects of supplementation, making it difficult for a single mineral to be beneficial.

The researchers also note that the participants were younger, with an average age of 66, and experienced less cognitive decline during the two-year study. As a result, there may be too little time in the trial to detect any protection from DHA supplementation.