Does cocoa make you smarter? The cognitive benefits of flavanols revealed

A team of scientists at the University of Birmingham has concluded people given a cocoa drink containing high levels of flavanols were able to compete cognitive tasks ‘more efficiently’ than when drinking a beverage not enriched with flavanols.

Study participants also underwent brain imaging to measure blood oxygenation levels in the brain. Working alongside experts at the University of Illinois at Urbana-Champaign, the researchers showed study participants who consumed a flavanol-rich drink produced a ‘faster and greater’ increase in blood oxygenation levels in response to artificially elevated levels of CO2 (hypercapnia).

Flavanols are a type of plant nutrient that occurs naturally in foods and drinks including cocoa, tea, red wine, blueberries, apples, pears, cherries, and peanuts.

“We used cocoa in our experiment, but flavanols are extremely common in a wide range of fruit and vegetables,”​ lead author Dr Catarina Rendeiro noted.

Flavanols are known to have a beneficial effect on cardiovascular health, but their effects on brain health are not well understood, the researchers suggested. 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.

“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,”​ Dr Rendeiro suggested.

Blood oxygenation boosts brain function

In the study, 18 healthy male participants aged 18-40 underwent a ‘standard procedure’ to challenge the brain’s blood circulation that involves breathing 5% carbon dioxide – about 100 times the normal concentration in air, producing an effect called hypercapnia.

Non-invasive near-infrared spectroscopy, a technique that uses light to capture changes in blood oxygenation levels, was used to track the increases in brain oxygenation in the frontal cortex in response to this carbon dioxide challenge.

Each participant underwent the test before and after drinking a cocoa drink on two occasions. On one of those, the drink was enriched with flavanols – on the other it was not.

Following the carbon dioxide test, the participants were asked to complete a number of progressively complex cognitive tests.

After taking the flavanol-enriched drink, participants had the highest levels of blood oxygenation in response to hypercapnia, reaching levels up to three times higher than when the non-flavanol-enriched drink was consumed. They also achieved these elevated levels one minute faster.

In the cognitive tests, the researchers found ‘significant differences’ in the speed and accuracy with which volunteers completed the higher complexity tasks. Volunteers who had taken the flavanol-enriched drink performed 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,”​ explained 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.”​

‘Very fit’ have no room for improvement

While the general trend held that flavanol consumption boosted blood oxidation, the researchers noted that within the study cohort a ‘small group’ did not benefit from flavanol consumption, either in terms of blood oxygenation or cognitive benefit.

This group was shown to have existing high levels of brain oxygenation responses to start with.

“This may indicate that some individuals, that perhaps are already very fit, have little room for further improvement,”​ explained 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.”​

Source​
‘Dietary flavanols improve cerebral cortical oxygenation and cognition in healthy adults’​
Scientific Reports​
DOI: https://doi.org/10.1038/s41598-020-76160-9
Authors: Gabriele Gratton, Samuel R. Weaver, Claire V. Burley, Kathy A. Low, Edward L. Maclin, Paul W. Johns, Quang S. Pham, Samuel J. E. Lucas, Monica Fabiani & Catarina Rendeiro