Certain plant compounds seem to protect against age-related memory impairment. A recent study has now been able to prove a direct, albeit weak, effect for the first time: flavanols are found in berries, apples and pears, for example, but also in green tea and the cocoa bean. They act as antioxidants in the body against inflammation and belong to the group of flavonoids, plant pigments that give color to vegetables and fruits, from apricot to eggplant.

Johanna Kuroczik

Editor in the "Science" section of the Frankfurter Allgemeine Sonntagszeitung.

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For the study by scientists from Columbia University in the United States and Brigham and Women's Hospital, Harvard University Teaching Hospital, 3500 healthy older adults over three years took either a placebo or a pill containing 500 milligrams of flavanol, which is in the upper range of nutrition experts' recommendation for the daily dose. At the beginning of the study, the diet of the study participants was analyzed and they underwent memory tests, which were repeated every year during the study period.

A third of the subjects also gave urine samples in which biomarkers for the flavanol content of the diet could be identified. This made it possible to determine how high the flavanol level was in the body of the study participants.

Overall, the results in memory tests did not improve much in those who also took flavanols. The positive effect was apparently only evident when people had previously eaten unhealthily and had a deficiency. However, their memory performance improved by 10.5 percent compared to those who had swallowed a placebo, and by 16 percent when compared to their results at the beginning of the study. The results were published in "PNAS".

Positive effect was only seen in flavanol deficiency

However, the number of studies on plant pigments has so far been thin – and mixed: Another study recently showed that flavonols do not improve memory performance in old age. However, the researchers at Columbia University explain that this is due to the fact that this study did not specifically examine whether the subjects were deficient in the plant pigments before the start of the study. According to study author and neurologist Scott Small of Columbia University, the two studies showed: "Flavanols have no effect in people who are not flavanol deficient."

The plant substances are said to have a beneficial effect on the hippocampus, a brain region that is crucial for memory formation. For example, they promote the connection between neurons. In mice, scientists were able to show that flavanols promote the growth of blood vessels in this region.

The fact that memory deteriorates with age probably has nothing to do with Alzheimer's or other dementias. "It's safe to assume that age-related memory loss occurs sooner or later in just about everyone, although there are big differences," says Small.

Other scientists are critical of the study. David Curtis, a scientist at the UCL Genetics Institute at University College London, told the UK's Science Media Center that the study did not prove the positive benefits of flavanols on memory function. "While the authors claim that some results are statistically significant, I think that's because the analyses were done incorrectly." You don't have to change your diet because of the study, he says.

However, it is important to eat enough vegetables and fruit. Nutrition experts like to say that you should eat as colorful as possible in order to absorb the different plant pigments. Studies have already pointed to other health-promoting effects of flavonoids, such as cardiovascular health. By the way, chocolate is of little help, only dark chocolate contains small amounts of flavonoids.