In the journals

Flavanols give fruits and vegetables their bright colors. They are also found in tea and cocoa. Observational studies have shown that eating foods rich in flavanols is linked with less cognitive decline as people age. New research suggests a possible reason why: flavanols appear to improve blood flow to the brain.

Researchers gave cocoa flavanols to 18 healthy adults in two separate trials. In one, the people consumed a cocoa drink with about 681 milligrams (mg) of flavanols. In the other, they had a cocoa drink with about 4 mg of flavanols. About two hours after having the cocoa drink, participants briefly inhaled air with high concentrations of carbon dioxide to raise their blood level above normal. (The brain's normal response to high blood carbon dioxide levels is to increase both blood flow to the brain and its uptake of oxygen.) The researchers then measured the speed of brain oxygenation and administered a set of mental tasks to assess cognitive performance. People had a faster brain oxygenation response after consuming high amounts of flavanols compared with lower amounts. They also scored higher on the cognitive tests and correctly solved problems 11% quicker.

The researchers suggested that the flavanols specifically increase blood flow to the brain's frontal cortex, the region responsible for planning and decision making. The results were published online Nov. 24, 2020, by Scientific Reports.