Low Flavanol Levels Linked to Memory Decline

A large study suggests that consuming flavanols through diet or supplements may improve cognitive performance — but only if flavanol levels are already deficient.

To conduct the research — published in Proceedings of the National Academy of Sciences — Columbia University Irving Medical Center researchers collaborated with scientists from Brigham and Women's Hospital and recruited 3,562 healthy older adult participants. The team randomly assigned the participants either a placebo or a daily supplement that contained 500 mg of cocoa-derived flavanols.

At the study's onset, each participant completed a survey assessing their diet quality and performed web-based activities designed to evaluate specific short-term memory processes governed by the hippocampus. The participants completed this memory assessment again one, two, and three years later.

The scientists also tested urine samples from just over one-third of the participants for flavanol biomarkers.

After analyzing the data, the team found that memory scores only slightly improved among those taking the flavanol supplement. But most of these participants were already eating foods rich in flavanols.

However, at the end of the first year, participants with a poorer diet or lower initial flavanol levels taking the supplement experienced a 16% increase in memory scores compared to baseline and a 10.5% increase in scores compared to those who took the placebo. Moreover, this improvement was maintained over the next two years.

The scientists suggest that although taking supplements had no significant impact on those who already had adequate flavanol levels, flavanol deficiency may drive age-related memory loss associated with the hippocampus.

In a news release, senior author Scott Small, M.D., a Boris and Rose Katz Professor of Neurology at Columbia University Vagelos College of Physicians and Surgeons, explains, "we cannot yet definitively conclude that low dietary intake of flavanols alone causes poor memory performance, because we did not conduct the opposite experiment: depleting flavanol in people who are not deficient."

However, Small adds that the next steps include conducting a clinical trial to confirm flavanol's impact on the brain by restoring flavanol levels in participants with a deficiency.

The study was supported by grants from Mars Edge, a segment of Mars Inc. — makers of chocolate candy bars and other food products — and the National Institutes of Health. However, authors from Mars Edge did not have a role in the study's statistical analysis.

Despite the study's claims, expert reactions to the findings offer a different perspective. For example, in a Science Media Center (SMC) roundup, Carl Hodgetts, Senior Lecturer of Cognitive Neuroscience, Royal Holloway, University of London, says: "While the initial results from this study are interesting, the relevance of these findings to the hippocampus and aging-related diseases like dementia are somewhat overstated in the paper."

David Curtis, Honorary Professor, UCL Genetics Institute, notes: "If anything, this study shows that flavanol supplements do not have any major effect on memory function. The study fails to provide evidence that increasing flavanol intake is beneficial and there is no need for anybody to contemplate changing their diet in the light of its findings."

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