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A large-scale study by researchers at Columbia and Brigham and Women’s Hospital/Harvard is the first to establish that a diet low in flavanols, nutrients found in certain fruits and vegetables, causes memory loss linked to age.
The study found that flavanol intake in older adults tracks scores on tests designed to detect memory loss due to normal aging and that replenishment of these bioactive dietary components in mildly flavanol-deficient adults over the age of 60 years improves the performance of these tests.
“The improvement among study participants on low flavanol diets was substantial and raises the possibility of using high flavanol diets or supplements to improve cognitive function in older adults,” says Adam Brickman. , Ph.D., professor of neuropsychology at Columbia University Vagelos. College of Physicians and Surgeons and co-lead of the study.
The finding also supports the emerging idea that the aging brain needs specific nutrients for optimal health, just as the developing brain needs specific nutrients to develop properly.
“Identifying the nutrients essential to the proper development of an infant’s nervous system was the crowning achievement of 20th century nutritional science,” says study lead author Scott Small, MD, Boris Professor of Neurology and Rose Katz at Columbia Vagelos College. doctors and surgeons.
“In this century, as we live longer, research is beginning to reveal that different nutrients are needed to fortify our aging minds. Our study, which relies on biomarkers of flavanol consumption, can be used as a model by other researchers to identify other nutrients needed nutrients.”
Age-related memory loss linked to changes in the hippocampus
The current study builds on more than 15 years of research in Small’s lab linking age-related memory loss to changes in the dentate gyrus, a specific area of the brain’s hippocampus – a region vital for learning new memories – and showing that flavanols improved function in this region of the brain.
Further research, in mice, found that flavanols, specifically a bioactive substance in flavanols called epicatechin, improved memory by enhancing the growth of neurons and blood vessels and in the hippocampus.
Next, Small’s team tested flavanol supplements in humans. A small study has confirmed that the dentate gyrus is linked to cognitive aging. A second, larger trial showed that flavanols improved memory by acting selectively on this region of the brain and had the greatest impact on those who started with a poor quality diet.
In the new study, the Columbia team collaborated with researchers at Brigham and Women’s Hospital to investigate the effects of flavanols and multivitamins in COSMOS (COcoa Supplements and Multivitamin Outcomes Study). The current study, COSMOS-Web, was designed to test the impact of flavanols in a much larger group and to determine whether a flavanol deficiency leads to cognitive aging in this area of the brain.
The study, titled “Dietary flavanols restore hippocampal-dependent memory in older adults with substandard diets and habitual flavanol intake,” was published in Proceedings of the National Academy of Sciences.
Over 3,500 healthy seniors were randomly assigned to receive a daily flavanol supplement (in pill form) or a placebo pill for three years. The active supplement contained 500mg of flavanols, including 80mg of epicatechins, an amount adults are advised to obtain from food.
At the start of the study, all participants completed a survey that rated the quality of their diet, including foods known to be high in flavanols. Participants then performed a series of web-based activities in their own homes, designed and validated by Brickman, to assess the types of short-term memory governed by the hippocampus. The tests were repeated after years one, two and three. Most participants identified as non-Hispanic and white.
More than a third of participants also provided urine samples that allowed researchers to measure a biomarker of dietary flavanol levels, developed by study co-authors at the University of Reading in the UK. , before and during the study. The biomarker gave researchers a more accurate way to determine if flavanol levels matched performance on cognitive tests and to ensure that participants were sticking to their assigned diet (compliance was high throughout the study). Flavanol levels varied moderately, although no participant was severely flavanol deficient.
People with mild flavanol deficiency benefited from a flavanol supplement
Memory scores improved only slightly for the entire group taking the daily flavanol supplement, most of whom already had a healthy diet high in flavanols.
But at the end of the first year of taking the flavanol supplement, participants who reported poorer diets and lower baseline flavanol levels saw their memory scores increase by an average of 10.5% per compared to placebo and 16% compared to their baseline memory. Annual cognitive testing showed that the improvement observed at one year was maintained for at least two more years.
The results strongly suggest that flavanol deficiency is a factor in age-related memory loss, the researchers said, as flavanol intake correlates with memory scores and flavanol supplements improve memory in memory-deficient adults. flavanols.
The results of the new study are consistent with those of a recent study, which found that flavanol supplements did not improve memory in a group of people with a range of baseline flavanol levels. The previous study did not separately examine the effects of flavanol supplements on people with low and high flavanol levels.
“What both studies show is that flavanols have no effect on people who don’t have a flavanol deficiency,” Small says.
It is also possible that the memory tests used in the previous study did not assess memory processes in the area of the hippocampus affected by flavanols. In the new study, flavanols only improved memory processes mediated by the hippocampus and did not improve memory mediated by other areas of the brain.
“We cannot yet conclude definitively that low dietary flavanol intake alone leads to poor memory performance, because we have not conducted the reverse experiment: depleting flavanols in people who are not deficient “says Small, adding that such an experiment could be considered unethical.
The next step needed to confirm the effect of flavanols on the brain, says Small, is a clinical trial to restore flavanol levels in adults with severe flavanol deficiency.
“Age-related memory decline is thought to occur sooner or later in almost everyone, although there is great variability,” says Small. “If some of this discrepancy is partly due to differences in dietary flavanol intake, we would see an even more dramatic improvement in memory in people who replenish dietary flavanols when they are in their 40s and 50s.”
Brickman, Adam M. et al, Dietary flavanols restore hippocampal-dependent memory in older adults with lower quality diets and lower habitual flavanol intake, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2216932120
Proceedings of the National Academy of Sciences