A brief flavanol overview:
Flavonoids, as secondary plant compounds, are among the so-called polyphenols (i.e. group of chemical compounds in fruits and vegetables). As they are responsible for the colouring of plants, they colour several vegetables and fruits, such as apples or soybeans. A certain group of flavonoids (i.e. proanthocyanidins) are most abundant in berries, red wine, apples, as well as tea, nuts or even chocolate - more precisely the cocoa bean. According to the data of theUnited States Department of Agriculture(short: USDA), the cocoa bean contains the following amounts of certain types of flavonoids per 100g:
- 156.67 mg epigallocatechin
- 99.18 mg epicatechin (hereinafter referred to as epicatechin)
- and 88,45 mg catechin
The content of these secondary plant compounds decreases with increasing processing. Consequently, cocoa mass from lightly fermented cocoa beans has more flavanols than dark chocolate - which in turn contains more substances than milk chocolate. Environmental and storage conditions, variety, degree of ripeness and fat content can also determine the flavanol content.
Several studies have investigated different effects of flavanol-containing cocoa beans or chocolate on glucose tolerance, cardiovascular disease and blood pressure. Now, a US study investigated the association with cognitive abilities in adults.
Study method with learning tests:
For this purpose, 211 healthy adults aged 50 to 75 years were studied in the controlled, randomized, parallel-arm study using a dietary questionnaire. The study participants took either 260mg, 510mg or 770mg of cocoa flavanols or placebos for 12 weeks in order to evaluate the effect. The study phase was accompanied by a so-called washout period.
The primary endpoint was a newly developed object recognition task located in a specific part of the hippocampus (i.e. area in the brain). For this, the study participants saw different patterns on a screen one after the other, and were asked to click whenever one of these patterns appeared a second time. According to evaluations, however, this test proved to be too difficult, since mostly only random hits could be seen.
Consequently, a secondary outcome was evaluated, using a list-learning task and list-orientation task. Subjects were asked to memorize as many words as possible from a list using a conventional learning test (so-called: Modified Rey auditory verbal learning test). Study participants who consumed the highest amount of flavanols in the previously evaluated questionnaire achieved the best results in the list test. However, subjects with the lowest plant substance intake showed the greatest improvements by taking flavanol tablets during the study phase. After the end of the intervention, the test results deteriorated again.
The effect was measured using a so-called alternative healthy diet index and a biomarker (i.e. measurable parameter as a reference for biological processes) for flavanol intake (short: gVLM). In a partial MRI study, cerebral (i.e., brain) blood volume of the hippocampus was measured before and after treatment. MRI, or magnetic resonance imaging, can be used to measure brain activity during the testing period by looking at blood flow in the brain region.
In a final test, study participants sorted objects by properties such as "size." In this case, treatment with the secondary plant compound led to an improvement in the results.
Object recognition and list sorting performance did not correlate with diet quality and did not improve after ingestion of flavanols. However, hippocampus-dependent list learning performance was directly associated with diet quality, according to study results, and improved after flavanols ingestion - especially in participants in the bottom third of diet evaluation.
According to study results, a possible association can be inferred between flavanol intake such as from cocoa or other plants and an increase in cognitive performance.
While further research on a larger scale is needed, in general, these results suggest that diet - and flavanols in particular - have a correlation with aging hippocampal memory function and normal cognitive decline. What implications these findings have in everyday life can only be determined by further study.