Studies support the role of cocoa flavanols — substances found in chocolate, as well as fruits and vegetables — in boosting memory and cognition. In new research published today in the journal Scientific Reports, scientists have found that flavanols can triple the maximal oxygenation of the brain. The authors also performed their own cognitive tests, confirming previous findings that flavanols improve cognitive performance even in healthy adults.

Chocolate: not only tasty, but also smart

In a 2017 meta-analysis (a study of studies) of the scientific literature on flavanols and their effects on the brain published until that date, researchers from the University of L’Aquila and the University of Rome found that flavanols had good neuroprotective properties, meaning they help maintain neuron health and function.

Participants in randomized controlled trials analyzed by the researchers from Italy showed greater performance in working memory, an improved ability to process visual information, and other similar ‘upgrades’ in cognitive abilities after consuming cocoa flavanols in the form of chocolate. The most benefits were seen in women, those who suffer from chronic sleep deprivation, and the elderly.

But how exactly does cocoa boost brainpower? Researchers aren’t completely sure, but cocoa flavanols seem to have important benefits for cardiovascular health and can increase cerebral blood volume. In a new study, researchers led by Catarina Rendeiro, a researcher and lecturer in nutritional sciences at the University of Birmingham, employed functional near-infrared spectroscopy — a state of the art optical brain imaging technique that involves placing multiple light sources and detectors close to the brain during measurements — in order to investigate the effects of flavanols in unprecedented detail.

“I have been for the last 10- 12 years interested in the health benefits of plant-derived flavonoids, particularly their effects on brain and cognitive function. We have known for many years that flavanols from cocoa (in particular) can improve vascular function in humans by improving vessel/arterial function. These benefits are apparent even after one single dose. However, the extent to which some of these benefits could translate into the brain vasculature was less clear,” Rendeiro told ZME Science.

For their study, the researchers tested 18 healthy participants before intake of cocoa flavanols and in two separate trials, one in which they received flavanol-rich cocoa and another during which they received processed cocoa with very low levels of flavanols. This was a double-blind study, meaning neither the participants nor researchers knew which type of cocoa was consumed in each of the trials.

Two hours after they consumed foods containing varying amounts of the antioxidant found in cocoa, the participants had to breathe air with 5% CO2 — which is about 100 times the normal concentration in the air — in order to increase blood flow to the brain. In response to the excess CO2, the brain naturally brings in more oxygen, which the researchers measured using custom-made helmets.

“The helmets themselves are quite interesting looking so I think the volunteers enjoyed having their pictures taken wearing them,” said Rendeiro, who also found taking a selfie with the futuristic-looking helmet irresistible.

The researchers found that cocoa flavanols improved the levels of blood oxygenation in the frontal cortex, a brain region that plays a key role in planning, regulating behavior, and decision-making. Oxygenated hemoglobin rose approximately three times higher for participants who consumed high-flavanol cocoa compared to those who ingested low-flavanol cocoa. What’s more, in the flavanol-rich group the oxygenation response was about one minute faster.

Participants also experienced improvements in cognitive performance in tasks that measure executive function (higher-level cognitive skills you use to control and coordinate your other cognitive abilities and behaviors), solving problems 11% faster than they did at baseline or when they consumed cocoa with reduced flavanols. However, these cognitive improvements surfaced only when the cognitive challenge was high.

“Improvements in Oxygenation levels during CO2 challenge might be linked to cognitive performance outcomes. 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,” Rendeiro said.

“I would just add that one exciting moment for us scientists when running a double-blind study like this (i.e., a study in which neither participants nor experimenters know the conditions while running the study for optimal control) is when the analysis is finished and the codes are open, and we finally know that the study has worked perfectly,” Prof. Monica Fabiani of the University of Illinois at Urbana-Champaign, co-author of the new study.

If these findings trigger an urge to stock up on chocolate, it should be pointed out that, while there are no side effects to flavanols, eating too much chocolate can be detrimental due to the intake of added sugar and fats. However, fruits and vegetables are excellent sources of flavanols.

“Consuming foods rich in flavanols, such as grapes, green tea, apples, berries can provide levels of flavanols that are beneficial for brain function. The fact that we can see benefits even in a perfectly healthy brain it is good news for all of us. There shouldn’t be any downsides from consuming flavanols from fresh fruits and vegetables,” Rendeiro said in an email.

Looking into the future, the researchers plan on using the same techniques to measure brain oxygenation in the elderly and those at risk of cardiovascular disease to test whether the benefits of flavanols extend to populations that are likely to benefit the most from them.

“I think 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,” Rendeiro added.