Does cocoa make us smarter?

According to new research at the University of Birmingham, increased consumption of flavanols – a group of molecules that occur naturally in fruit and vegetables – can increase your mental agility.

A team in the University’s School of Sport, Exercise and Rehabilitation Sciences found that people given a cocoa drink containing high levels of flavanols could complete certain cognitive tasks more efficiently than when drinking a non-flavanol enriched-drink.

The study participants also underwent non-invasive brain imaging to measure blood oxygenation levels in the brain. A group of researchers from the University of Illinois showed that participants who had consumed the flavanol-rich drink produced a faster and more significant increase in blood oxygenation levels in response to artificially elevated levels of CO₂.

Flavanols, a sub-group of plant flavonoids, are present in cocoa, grapes, apples, tea, berries, and other foods. They are known to have a beneficial effect on cardiovascular health, but their impact on brain health is not well understood. This study, published in Scientific Reports, is the first time the cognitive effects of flavanols in young, healthy subjects and the link with brain blood oxygenation have been investigated.

Lead author, Dr. Catarina Rendeiro, of the University of Birmingham’s School of Sport, Exercise and Rehabilitation Sciences, explains: “We used cocoa in our experiment, but flavanols are extremely common in a wide range of fruit and vegetables. By better understanding the cognitive benefits of eating these food groups, as well as the wider cardiovascular benefits, we can offer improved guidance to people about how to make the most of their dietary choices.”

All participants underwent a test before & after drinking cocoa on two occasions, and on one of those occasions, the drink was enriched with flavanols. Following the carbon dioxide test, the participants were asked to complete several progressively complex cognitive tests.

Participants who had taken the flavanol-enriched drink had the highest levels of blood oxygenation in response to hypercapnia, reaching levels up to three times higher than participants drinking the non-flavanol-enriched drink. They also achieved these elevated levels 1 minute faster than participants who drank the non-enriched cocoa.

In the cognitive tests, the researchers found significant differences in the speed and accuracy with which volunteers completed the higher complexity tasks, with volunteers who had taken the flavanol-enriched drink performing the tasks 11% faster on average.

“Our results showed a clear benefit for the participants taking the flavanol-enriched drink – but only when the task became sufficiently complicated,” explains Dr. Rendeiro.

“We can link this with our results on improved blood oxygenation – if you’re being challenged more, your brain needs improved blood oxygen levels to manage that challenge. It also further suggests that flavanols might be particularly beneficial during cognitively demanding tasks”.

The researchers also noted a further outcome. Within the study cohort, a small group did not benefit from the flavanol-enriched drink in terms of blood oxygenation levels and did not derive any cognitive benefit. This group was shown to have existing high levels of brain oxygenation responses to start with that were not increased further by drinking the enriched cocoa. “This may indicate that some individuals, that perhaps are already very fit, have little room for further improvement”, explain by Dr. Rendeiro.

“The small group of participants who did not react to the flavanol gives us additional evidence to confirm the link between increased brain blood oxygenation and cognitive ability,” adds Dr. Rendeiro.