The low-flavanol diet causes age-related memory loss

A large-scale study led by Columbia and Brigham and Women’s Hospital/Harvard researchers is the first to show that a diet deficient in flavanols (nutrients found in some fruits and vegetables) contributes to age-related memory loss.

A new study discovered that flavanol consumption among older persons correlates with outcomes on tests designed to detect memory loss related to normal aging and that replenishing these bioactive dietary components improves performance in mildly flavanol-deficient adults over 60. 

Adam M. Brickman, Ph.D., professor of neuropsychology at Columbia University Vagelos College of Physicians and Surgeons and co-leader of the study, said, “The improvement among study participants with low-flavanol diets was substantial and raised the possibility of using flavanol-rich diets or supplements to improve cognitive function in older adults.” 

The discovery also supports the growing idea that the aging brain requires specific nutrients for optimal health, just as the young brain requires specific nutrients for proper development. 

The study’s senior author, Scott A. Small, MD, the Boris and Rose Katz Professor of Neurology at Columbia University Vagelos College of Physicians and Surgeons, said, “Identifying nutrients critical for the proper development of an infant’s nervous system was a crowning achievement of 20th-century nutrition science.” 

He added, “In this century, as we live longer, research is starting 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 template by other researchers to identify additional, necessary nutrients.”

This study extends more than 15 years of work in Small’s group that has connected alterations in the dentate gyrus, a particular region of the brain’s hippocampus, to age-related memory loss. Additionally, studies in mice showed that flavanols enhanced the growth of neurons and blood vessels in the hippocampus, which improved memory. Then, Small’s team put flavanol supplements to the test on humans.

According to one small study, the dentate gyrus is associated with cognitive aging. A second, more detailed study revealed that flavanols enhanced memory by working specifically on this brain region and had the most significant effects on people who began with a poor diet.

The Brigham and Women’s Hospital and Columbia teams worked together to examine the effects of flavonols and multivitamins in COSMOS. 

The current study, COSMOS-Web, aimed to examine whether a lack of flavanols contributes to cognitive aging in this region of the brain by testing the effects of flavanols on a much wider population. 

A daily flavanol supplement (a tablet) or a placebo pill was randomly given to more than 3,500 healthy older individuals for three years.

The number of flavonols in the active supplement was 500 mg, including 80 mg of epicatechins, the recommended daily intake for adults. 

In order to determine the forms of short-term memory controlled by the hippocampus, each participant completed a survey to rate the quality of their diet. They then each completed a series of exercises online in the comfort of their own homes.

The exams were administered again after years one, two, and three. The majority of interviewees described themselves as white and non-Hispanic.

More than a third of the individuals also provided urine samples, which allowed researchers to assess dietary flavanol levels before and during the study using a biomarker created by co-study authors at Reading University in the UK. 

The biomarker allowed the researchers a more accurate approach to check if individuals were adhering to their prescribed regimen and see if flavanol levels correlated with performance on the cognitive tests. Although there was some variation in flavanol levels, no participant had significant flavanol deficiency.

According to the findings of a new study, Flavanol deficiency appears to be a driver of age-related memory decline, as flavanol consumption is linked with memory scores and flavanol supplementation enhanced memory in flavanol-deficient people. The study’s findings are consistent with a recent study that indicated flavanol pills did not improve memory in a group of persons with varying baseline flavanol levels.

It is possible that the previous study’s memory tests did not examine memory processes in the hippocampus area affected by flavanols and that flavanols only improved memory processes governed by the hippocampus and did not improve memory mediated by other brain sections.

Small said, “We cannot yet definitively conclude that low dietary intake of flavanols causes poor memory performance. We did not conduct the opposite experiment: depleting flavanol in people who are not deficient, adding that such an experiment might be considered unethical.”

According to Small, the next step in confirming flavanols’ effect on the brain is a clinical experiment to restore flavanol levels in people with severe flavanol deficiency.

Small said, “Age-related memory decline is thought to occur sooner or later in nearly everyone, though there is a great amount of variability; if some of this variance is partly due to differences in dietary consumption of flavonols, then we would see an even more dramatic improvement in memory in people who replenish dietary flavanols when they’re in their 40s and 50s.”

Mars Edge, a division of Mars Inc., and the National Institutes of Health funded the study. 

Journal Reference:

1. Adam M. Brickman, Lok-Kin Yeung, etal. Dietary flavanols restore hippocampal-dependent memory in older adults with lower diet quality and habitual flavanol consumption. Proceedings of the National Academy of Sciences.DOI:10.1073/pnas.2216932120