Scientists at Harvard's Brigham Women's Hospital and Columbia University's Irving Medical Center have found that a diet low in flavanols, found in certain fruits and vegetables, leads to age-related memory loss. The results of the study are published in the journal Proceedings of the National Academy of Sciences (PNAS).

Previous studies have shown that consumption of dietary flavanols may support memory function during aging, with the effect of flavonols being dependent on the quality of dietary habits. To test these hypotheses, the researchers conducted a large-scale study involving 3562 elderly people who were randomly divided into two groups. In one, people consumed cocoa extract (500 milligrams of flavonols per day) for three years, and in the other, a placebo.

All participants completed a survey that assessed the quality of their diet, including consumption of foods high in flavanols. The volunteers then completed a series of web-based activities at home to assess types of short-term memory associated with the hippocampus. The tests were repeated after one, two and three years. More than a third of the participants also provided urine samples to measure the biomarker of dietary flavanol levels.

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It is known that age-related memory loss is associated with changes in the dentate gyrus of the hippocampus, an area that is critical for the formation of new memories. Scientists have shown that flavonols selectively improve the activity of this area of the brain, enhancing the growth of neurons and blood vessels. They had the greatest effect if people initially adhered to poor-quality nutrition.

Memory scores improved only marginally for the group in which most people were already on a healthy diet. But at the end of the first year of flavanol supplementation, participants who reported eating worse and having lower baseline flavanol levels improved their memory scores by an average of 10.5 percent compared to placebo and 16 percent compared to baseline. Annual cognitive testing showed that the improvement observed within one year was maintained for at least another two years.

According to the authors of the study, the next step needed to confirm the effect of flavanols on the brain is a clinical trial to restore flavonol levels in adults with severe deficiency of these substances.