Can drinking cocoa make you smarter? Study suggests flavanol-rich drinks can increase people's mental agility
Drinking cocoa can increase your mental agility thanks to flavanols that are present in it, according to researchers. They found that people given a cocoa drink containing high levels of flavanols were able to complete certain challenging cognitive tasks more efficiently than when drinking a non-flavanol enriched-drink.
Participants who had consumed the flavanol-rich drink produced a faster and greater increase in blood oxygenation levels in the frontal cortex, a brain region that plays a key role in planning, regulating behavior and decision-making.
“One drink of cocoa flavanols improved levels of blood oxygenation within the frontal areas of the brain, by making oxygenated hemoglobin rise not only higher but also faster in comparison to a low-flavanol drink. Efficient oxygenation of the brain is key for cognition, and impairments in this process are common in people in older age or at higher risk of cardiovascular diseases or dementia. So, looking into the future, we would like to test whether these beneficial effects can be translated to these populations which are likely to be the ones that would benefit the most,” Dr Catarina Rendeiro, lecturer in nutritional sciences, School of Sport, Exercise & Rehabilitation Sciences, University of Birmingham, tells MEAWW.
Dr Rendeiro led the research with University of Illinois psychology professors Dr Monica Fabiani and Dr Gabriele Gratton. The authors stress that the findings can have important future implications for using dietary strategies containing plant-derived flavanols for enhancement of blood oxygenation and cognitive performance in healthy populations, as well as for populations at higher risk — such as smokers, hypertensives, diabetics, and older adults — or to help recover and treat brain injuries and disease.
“The fact that flavanols can be effective at improving cerebral oxygenation and cognitive function even in a healthy brain is a remarkable finding and it means that we can potentially all benefit from diets rich in flavanols,” emphasizes Dr Rendeiro.
The analysis
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 effects on brain health are not well understood. Accordingly, in the current analysis, published in Scientific Reports, the cognitive effects of flavanols in young, healthy subjects and the link with brain blood oxygenation were investigated.
The team recruited adult non-smokers with no known brain, heart, vascular or respiratory disease, reasoning that any effects seen in this population would provide robust evidence that dietary flavanols can improve brain function in healthy people. They tested 18 participants (aged between 18 and 40) before their intake of cocoa flavanols and in two separate trials, one in which the subjects received flavanol-rich cocoa and another during which they consumed processed cocoa with very low levels of flavanols.
Neither the participants nor researchers knew which type of cocoa was consumed in each of the trials. Such a double-blind study design prevents investigators’ or participants’ expectations from affecting the results.
About two hours after consuming the cocoa, participants breathed air with 5% carbon dioxide — about 100 times the normal concentration in the air — producing an effect called hypercapnia. This is a standard method for “challenging brain vasculature” to determine how well it responds, Dr Gratton explains. The body typically reacts by increasing blood flow to the brain. “This brings in more oxygen and also allows the brain to eliminate more carbon dioxide,” he adds.
With functional near-infrared spectroscopy, a technique that uses light to capture changes in blood flow to the brain, the team tracked increases in brain oxygenation in the frontal cortex in response to this carbon dioxide challenge. Following the carbon dioxide test, the participants were asked to complete several progressively complex cognitive tests.
The researchers found that the participants who had taken the flavanol-enriched drink had the highest levels of blood oxygenation, 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 investigators 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 correctly solving problems 11% faster on average. According to the authors, improvements in oxygenation levels during carbon dioxide challenge might be linked to cognitive performance outcomes. There was, however, no measurable difference in performance on the easier tasks.
“Young adults experienced improvements in cognitive performance in a Stroop-task (measures executive function), but only when the levels of the cognitive challenge were high. This suggests that the beneficial effects of flavanols may only emerge when the cognitive challenge is sufficiently high. Perhaps only when the oxygenation demands in the brain are high enough, a young healthy brain can actually benefit from the intake of flavanols,” Dr Fabiani tells MEAWW.
The researchers noted a further outcome. Within the study cohort, there was a small group (four out of 18) who did not benefit at all from the flavanol-enriched drink in terms of blood oxygenation levels, nor did their performance on the tests improve. 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.
“We further observed that there were a few volunteers that actually did not benefit from flavanol intake both in terms of cerebral oxygenation and cognitive performance. These individuals also happened to have the highest/healthiest blood oxygenation responses, so it seems that these individuals won’t benefit further from the intake of flavanols because they are performing already at their maximum. It is currently unclear why these subjects had higher responses but it might be related to higher levels of fitness, but we did not measure this in the study,” explains Dr Rendeiro.
She concludes that this small group “gives additional evidence to confirm the link between increased brain blood oxygenation and cognitive ability.”