Brain supplement evidence remains mixed, researchers say

Evidence for brain-health supplements remains uneven, despite a growing market aimed at people who want to preserve memory and attention as they age. Researchers writing in The Conversation said recent studies show that changes seen in the brain or body do not necessarily prove a product improves daily cognitive function.

Amanda Lloyd, Alexander Nigel William Taylor and Alina Warren-Walker said products marketed for brain health include fish oil capsules and postbiotics, which are nonliving compounds and byproducts made when beneficial gut bacteria digest fiber or prebiotics. They said assessing those products is difficult because studies often measure different outcomes and cannot always separate cause from association.

Omega-3 findings point in different directions

One recent study, cited by the authors, analyzed five years of data from the Alzheimer’s Disease Neuroimaging Initiative. Researchers found that older adults who reported using omega-3 supplements showed faster decline on several cognitive measures than matched people who did not report using the supplements.

According to the study, brain imaging also showed lower glucose metabolism in vulnerable brain areas among supplement users, suggesting those regions were using less of the brain’s main energy source. The Conversation authors stressed that the study was observational, meaning participants chose whether to take supplements and were not randomly assigned to omega-3s or a placebo.

Because of that design, the omega-3 study cannot show that the supplements caused faster decline, the authors said. Other differences between people who took supplements and those who did not may have affected the findings.

The authors also said the results should not be read as evidence that eating fish is harmful. They cited a 2023 meta-analysis of longitudinal studies that found dietary omega-3 intake was associated with a lower risk of dementia or cognitive decline, underscoring that supplements and foods are not interchangeable.

Biomarkers do not settle the question

A separate randomized controlled trial found that taking a daily multivitamin for two years was linked to a modest slowing in two epigenetic clocks, which estimate biological aging by tracking chemical marks on DNA. The trial authors said more work is needed to determine whether those small changes lead to health benefits people can notice.

Lloyd, Taylor and Warren-Walker said the contrast illustrates a central problem in supplement research. A product may shift a biomarker or alter brain activity without producing a clear improvement in memory, well-being or everyday tasks.

The authors said cognitive tests can help measure attention, working memory and other functions, but they can miss subtle changes, especially in healthy adults who already perform well. A person may get the same score on a task while the brain uses different patterns of activity to maintain that performance.

Their ongoing Better Brain Trial is testing whether nutrition-based products can change how the brain supports cognition before changes appear on standard tests. The authors said the trial’s results are still being analyzed and have not been published in a peer-reviewed journal.

In that randomized, double-blind, placebo-controlled study, adults over 55 took supplement combinations or matched placebos daily for 60 days. Participants completed working memory and attention tasks while researchers recorded brain activity with electroencephalography, or EEG.

The study used tasks including the n-back test, in which participants respond when a letter matches one shown earlier, and the Stroop task, which asks people to focus on one feature while ignoring a conflicting cue. The researchers also used metabolomics, a method that measures small molecules in blood, urine or other samples, to look for body-wide biological changes.

The Conversation authors said these tools may help researchers ask more precise questions, but none can prove on its own that a supplement protects the brain. They said evidence reviewed by the 2024 Lancet Commission on dementia prevention supports physical activity, social contact and management of long-term health risks such as high blood pressure.

This story draws on original reporting from Medical Xpress.