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Study finds dietary flavanols boost brain oxygenation and cognition in healthy adults – PsyPost

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Nov 27, 2020

The consumption of flavanols, naturally occurring compounds found in plants, is associated with cognitive and cerebrovascular benefits in health adults, according to new research published in Scientific Reports. The study provides evidence that flavanol intake results in faster and greater brain oxygenation in response to the buildup of carbon dioxide in the bloodstream.

“For the last 10 to 12 years, I have been interested in the health benefits of plant-derived flavonoids, particularly their effects on brain and cognitive function,” said study author Catarina Rendeiro, a lecturer in nutritional sciences at the School of Sport, Exercise and Rehabilitation Sciences at the University of Birmingham.

“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 were less clear.”

Given that we have more and more people suffering from cognitive impairments and neurodegenerative diseases later in life (and we are for the most part living longer), it is critical that we make the lifestyle choices (exercise, diet) that can maximize protection of the brain and help delay the onset of cognitive dysfunction when we age,” Rendeiro explained.

For their study, which used a double-blind methodology, the researchers tested 18 healthy male participants 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. The flavanol-rich cocoa contained 150 mg of epicatechin and 35.5 mg of catechin, while the low-flavanol cocoa contained less than 4 mg of both flavanols.

The participants 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, a brain region that plays a key role in planning, regulating behavior and decision-making.

The participants were then asked to complete a number of progressively complex cognitive tests.

The researchers found that the participants who had taken the flavanol-enriched drink tended to have more efficient tissue oxygenation responses in the frontal cortex. The improved brain oxygenation also appeared to translate into improvements in cognitive performance on higher complexity tasks (but not lower complexity tasks.)

The findings indicate that “consuming foods rich in flavanols, such as grapes, green tea, apples, berries and unprocessed cocoa powders can provide levels of flavanols that are beneficial for brain oxygenation and cognitive function,” Rendeiro told PsyPost.

“The fact that flavanols can be effective even in a healthy brain (where the physiology is working exactly as it should) is a remarkable finding and it means that we can potentially all benefit from diets rich in flavanols.”

But as with all research, the study includes a few caveats.

Women were not included in the study to ensure a more homogenous sample and to minimize the impact of hormonal fluctuations. “The impact of flavanols in women has not been addressed in this study, so it is possible that women respond differently. This is something that needs to be look at in the future,” Rendeiro explained.

“We also need to understand better the mechanisms underlying these beneficial effects. How are these compounds affecting oxygenation levels?”

“Efficient oxygenation of the brain is key for cognition and impairments in this process is common in people in older age or at higher risk of cardiovascular diseases or dementia. So, in the future it would be important to look at whether these beneficial effects we see in young people can be translated to at risk populations, as these are likely to benefit the most,” Rendeiro added.

Although the study examined flavanols from natural cocoa powders, ingesting chocolate would probably not produce the same effect.

“Many people tend to associate the benefits of cocoa with chocolate, but those are two very different things. The cocoas that contain flavanols are normally unprocessed. However, when you process cocoa beans to make chocolate (roasting, alkalization, etc.) the flavanol content declines,” Rendeiro explained.

“Unfortunately, it is difficult to know what the content of flavanols is in chocolate products as these are not disclaimed in labels. Generally, scientific articles that have measured content of flavanols in commercially available chocolates do not seem to find any relationships between content of cocoa solids and levels of flavanols.”

“So having more cocoa solids does not equate necessarily to more flavanol content. Importantly, even the chocolates that have the highest amounts of flavanols are still a little far from the effective doses. You would have to consume a substantial portion of chocolate to reach the desired doses and that wouldn’t be advisable given the concurrent intake of sugar and fat. Producing chocolate in ways that retain the content of flavanols should be a goal, so we can obtain effective doses of flavanols from small amounts of chocolate (1 to 2 squares),” Rendeiro said.

“The good news is consuming a variety of foods rich in flavanols, such as grapes, green tea, apples, berries, pulses can provide levels of flavanols that are beneficial for brain and vascular function.”

The study, “Dietary flavanols improve cerebral cortical oxygenation and cognition in healthy adults“, was authored by 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, and Catarina Rendeiro.

 

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