Flavanol Supplement Restores Memory in Adults With Poor Diets

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Flavanol Supplement Restores Memory in Adults With Poor Diets

Taking a daily flavanol supplement improves hippocampal-dependent memory in older adults who have a relatively poor diet, results of a large new study suggest.

There's increasing evidence that certain nutrients are important for the aging body and brain, study investigator Scott Small, MD, the Boris and Rose Katz Professor of Neurology, Columbia University Vagelos College of Physicians and Surgeons, told Medscape Medical News.

"With this new study, I think we can begin to say flavanols might be the first one that really is a nutrient for the aging brain."

These findings, said Small, represent "the beginning of a new era" that will eventually lead to formal recommendations" related to ideal intake of flavanols to reduce cognitive aging.

The findings were published online May 30 in the Proceedings of the National Academy of Science.

Better Cognitive Aging

Cognitive aging refers to the decline in cognitive abilities that are not thought to be caused by neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. Cognitive aging targets two areas of the brain: the hippocampus, which is related to memory function, and the prefrontal cortex, which is related to attention and executive function.

Previous research has linked flavanols, which are found in foods like apples, pears, berries, and cocoa beans, to improved cognitive aging. The evidence shows that consuming these nutrients might be associated with the hippocampal-dependent memory component of cognitive aging.

The new study, known as COcoa Supplement and Multivitamin Outcomes Study-Web (COSMOS-Web), included 3562 generally healthy men and women, mean age 71 years, who were mostly well-educated and non- Hispanic/non-Latinx White individuals.

Participants were randomly assigned to receive oral flavanol-containing cocoa extract (500 mg of cocoa flavanols, including 80 mg of epicatechin) or a placebo daily.

The primary endpoint was hippocampal-dependent memory at year 1 as assessed with the ModRey, a neuropsychological test designed to measure hippocampal function.

Results showed participants in both groups had a typical learning (practice) effect, with similar improvements (d = 0.025; P = .42).

Researchers used other tests to measure cognition: the Color/Directional Flanker Task, a measure of prefrontal cortex function, and the ModBent, a measure that's sensitive to dentate gyrus function. The flavanol intervention did not affect ModBent results or performance on the Flanker test after 1 year.

However, it was a different story for those with a poor diet at baseline. Researchers stratified participants into tertiles on the basis of diet quality as measured by the Healthy Eating Index (HEI) scores. Those in the lowest tertile had poorer baseline hippocampal-dependent memory performance but not memory related to the prefrontal cortex.

The flavanol intervention improved performance on the ModRey test compared with placebo in participants in the low HEI tertile (overall effect: d = 0.086; P = .011) but not among those with a medium or high HEI at baseline.

"We confirmed that the flavanol intervention only benefits people who are relatively deficient at baseline," said Small.

The correlation with hippocampal-dependent memory was confirmed in a subset of 1361 study participants who provided a urine sample. Researchers measured urinary 5-(3′,4′-dihydroxyphenyl)-gamma-valerolactone metabolite (gVLM) concentrations, a validated biomarker of flavanol consumption.

After stratifying these results into tertiles, researchers found performance on the ModRey was significantly improved with the dietary flavanol intervention (overall effect: d = 0.141; P = .006) in the lowest gVLM tertile.

Memory Restored

When participant in the lowest tertile consumed the supplement, "their flavanol levels went back to normal, and when that happened, their memory was restored," said Small.

It appears that there is a sort of ceiling effect to the flavanol benefits. "It seems what you need to do is normalize your flavanol levels; if you go above normal, there was no evidence that your memory keeps on getting better," said Small.

The study included only older adults so it's unclear what the impact of flavanol supplementation is in younger adults. But cognitive aging "begins its slippery side" in the 40s, said Small. "If this is truly a nutrient that is taken to prevent that slide from happening, it might be beneficial to start in our 40s."

He recognized that the effect size is not large but said this is "very dependent" on baseline factors and most study participants had a rather healthy diet. "None of our participants were really highly deficient" in flavanols, he said.

"To see a stronger effect size, we need to do another study where we recruit people who are very low, truly deficient, in flavanols, and then see what happens."

Showing that flavanols are linked to the hippocampal and not to the prefrontal component of cognitive aging "speaks to the mechanism," said Small.

Though the exact mechanism linking flavanols with enhanced memory isn't clear, there are some clues; for example, research suggests cognitive aging affects the dentate gyrus, a subregion of the hippocampus.

The flavanol supplements were well tolerated. "I can say with close to certainty that this is very safe," said Small, adding the flavanols have now been used in numerous studies.

The findings suggest flavanol consumption might be part of future dietary guidelines. "I suspect that once there is sufficient evidence, flavanols will be part of the dietary recommendations for healthy aging," said Small.

A Word of Caution

Commenting for Medscape Medical News, Heather M. Snyder, PhD, vice president of medical and scientific relations, Alzheimer's Association, said that though science suggests a balanced diet is good for overall brain health, no single food, beverage, ingredient, vitamin, or supplement has yet been proven to prevent dementia, treat or cure Alzheimer's, or benefit cognitive function or brain health.

Experts agree the best source of vitamins and other nutrients is from whole foods as part of a balanced diet. "We recognize that, for a variety of reasons, this may not always be possible," said Snyder.

However, she noted, dietary supplements are not subject to the same rigorous review and regulation process as medications.

"The Alzheimer's Association strongly encourages individuals to have conversations with their physicians about all medications and dietary supplements they are currently taking or interested in starting." 

COSMOS is supported by an investigator-initiated grant from Mars Edge, a segment of Mars Incorporated, a company engaged in flavanol research and flavanol-related commercial activities, which included infrastructure support and the donation of study pills and packaging. Small reports receiving an unrestricted research grant from Mars, Incorporated.

PNAS. Published online May 29, 2023. Full text