Cocoa could make you smarter and we finally know why

Several studies have already shown that flavanols, which are found in particular in cocoa beans, have a protective action on the cardiovascular system. Some findings have also suggested that diets rich in flavanols limit cognitive aging, although the exact action of these compounds has never been clearly understood. Researchers are now bringing new elements: the consumption of flavanols would lead to better brain oxygenation and improve our cognitive performance.

Poor nutrition and lack of exercise, among other factors, can accelerate cognitive aging and lead to dementia. However, there is epidemiological evidence to suggest that flavonoids – small molecules found in fruits and vegetables, which give them rather bright colors – may protect against vascular disease and cardiovascular mortality.

Flavanols are a subfamily of flavonoids. Among the plants richest in flavanols are the tea tree – green teas also contain much more than black teas – grapevine (red wine) and the cocoa tree. Dark chocolate contains about 53 mg of flavanols per 100 g, mainly in the form of (-) – epicatechin and (+) – catechin. This is a good reason to stop feeling guilty about eating chocolate! Okay, it’s almost Christmas …

More and faster oxygenation

In particular, it has been shown in the past that cocoa flavanols improve endothelial function fairly quickly (in just 1 or 2 hours) by accentuating the vasodilatory properties of peripheral arteries. The benefits observed in the clinical setting are even comparable to those induced by taking drugs such as statins. These effects of cocoa flavanols on endothelial function have been associated with increased bioavailability of nitric oxide (NO), or nitric oxide, an important neurotransmitter in mammals. It also has a vasodilating and bactericidal action. Another line of research suggests that flavanols may also limit the cognitive decline associated with aging. However, the relationship between circulatory NO levels and their effects on the cerebrovascular system and cognitive performance has been poorly understood.

Cerebral blood flow is controlled by neuronal activity, but also by arterial blood gas levels, particularly carbon dioxide (CO₂). However, NO is known to contribute to hypercapnia, which refers to an increase in the volume of CO₂ in the blood. Furthermore, cerebrovascular reactivity to CO₂ it is considered a key biomarker of cerebrovascular health and is closely related to cognitive function. Therefore, a team of American and British researchers set out to evaluate the underlying physiological actions of cocoa flavanols on vascular and cognitive brain functions in hypercapnia. The aim was to verify whether the improvement in endothelial function mediated by flavanols was or was not related to cerebrovascular and cognitive functions.

Eighteen healthy men, between the ages of 18 and 45, were recruited for this study. They had no history of cerebrovascular, cardiovascular, or respiratory disease; women were excluded from this study to minimize the impact of menstrual-related hormonal fluctuations. During the 24 hours prior to the experiment, participants were asked to refrain from consuming foods rich in polyphenols (fruit, vegetables, cocoa, coffee, tea, fruit juices and wine) and nitrates. Also, they shouldn’t consume alcohol or do strenuous exercise.

Each of the volunteers participated in two visits, at least two weeks apart, during which they randomly and double-blinded a drink with a high cocoa content (150 mg of (-) – epicatechin + 35.5 mg of catechin) or low flavanol content (less than 4 mg of both compounds). The researchers performed their analyzes 2 hours after ingesting the drinks.

An interest in complex intellectual tasks

To measure cerebrovascular reactivity, they subjected the participants to a breathing exercise (4 minutes, in air composed of 5% CO₂), consisting in increasing the partial blood pressure of CO₂ (hypercapnia). MRI observation allowed to follow the evolution of the oxyhemoglobin concentration in the participants’ brains. Result: the same frontal cortical regions were oxygenated, whether the drink consumed was rich or low in flavanols. On the other hand, in people who consumed a lot of flavanols, it appears that oxygenation was much faster: it took almost 3 minutes for their brain to reach 90% of maximum oxygenation (versus almost 5 minutes for the other group. ).

The team then assessed the cognitive performance of the two groups, using the Stroop experiment, which assesses the brain’s ability to focus on a particular element despite “spurious” information. Very concretely, it is about identifying the color of a word that designates the name of a color (“blue”, “red”, “green”, etc.), knowing that the word in question can be written in a color other than what it designates (which complicates the task of the brain and requires very great concentration). The researchers here measured the time it took the participants to respond.

Here, too, the group that consumed the flavanol-enriched drink was more efficient. Participants in this group responded more quickly to the test and made fewer mistakes. Note that in the case of less complex cognitive tests, the researchers did not notice, however, any significant influence of flavanol consumption.

The results of this study thus highlighted the fact that, during hypercapnia, the flavanols contained in cocoa not only improve the oxygenation of the brain (which is more important and faster), but also increase cognitive abilities. when it comes to performing a complex task. The researchers therefore suggest that the underlying mechanisms at play may be similar to those identified in the peripheral vascular system and therefore, that the increase in NO in the cerebral arteries, induced by hypercapnia, influences cognitive functions.

Now you know it can be useful to munch on a few squares of chocolate about two hours before thinking hard! The authors also point out that these beneficial effects could also be observed after ingesting other foods rich in flavanols, such as beans, blackberries, grapes, apples, etc. They add that their findings also constitute a potential avenue for the treatment and recovery of brain injuries.

Source: Scientific Reports, G. Gratton et al.