Written by Joyce Smith, BS. Study results showed that brains of healthy adult participants recovered faster and performed better on complex cognitive tests when drinking a flavanol-enriched cocoa beverage prior to a mild vascular challenge.
Flavanols are a sub-group of plant flavonoids that give fruits and vegetables their bright colors. They are present in cocoa, grapes, apples, tea, berries, and other foods and are known to benefit vascular function 1-3. Studies have found that flavonoids can rapidly dilate peripheral arteries within 1-2 hours, thus enabling flavanols to improve endothelial function in humans 4. Improved endothelial function has been linked to increased nitric oxide (NO) bioavailability 5 which, when compromised, has been shown to contribute to heart disease 6. However, the flavanol effect on brain health and cognitive function is not well understood. While existing evidence suggests that cocoa flavanols may increase NO bioavailability, new evidence suggests a protective role of plant flavanols in cognitive decline 6,7.
In a randomized double-blind placebo controlled cross-over study 8 of healthy young adults, researchers investigated whether flavanols in cocoa would increase circulatory levels of NO to benefit the brain vasculature, and positively impact cognitive performance in humans by providing faster and greater brain oxygenation during hypercapnia (high blood levels of carbon-dioxide [CO2]).
Eighteen healthy nonsmoking males, aged 18–40 years, underwent a carbon-dioxide (CO2) challenge. By breathing 5% carbon-dioxide (which is 100 times the normal air concentration) they were able to increase their CO2 blood levels and induce hypercapnia. The CO2 challenge is a standard method for challenging brain vasculature to determine how well it responds to elevated brain CO2 levels. Typically the body responds by increasing oxygenated blood flow to the brain, thus allowing the brain to release excess carbon dioxide. In this study, researchers used non-invasive near-infrared spectroscopy to measure the brain’s resilience to excess carbon dioxide. Near-infrared spectroscopy uses light to capture changes in blood oxygenation levels and can detect increases in brain oxygenation in the frontal cortex in response to a CO2 challenge. Participants underwent the CO2 challenge before and after drinking a high- or low- cocoa drink and repeated the challenge after drinking the placebo. On one of those occasions, the drink was enriched with flavanols. Following the CO2 challenge, the participants were asked to complete a number of progressively more complex cognitive tests.
When participants drank the flavanol-enriched cacao followed by the CO2 challenge, they reached blood oxygenation levels in the brain that were higher and also achieved faster compared to those who drank the placebo (non-flavanol-enriched drink) [F(1,16) = 6.08, p = 0.025]. When comparing high- to low-flavanol cocoa consumption, the high-flavanol cocoa drinkers reached maximal oxygenation levels that were more than three times higher than the low-flavanol cocoa drinkers (t(16) = − 2.37, p = 0.030) and achieved 90% maximal oxygenation about one minute faster at 2 hours post CO2 challenge (F(1, 16) = 13.61, p = 0.001). The flavanol-enriched drinks also allowed participants to perform cognitive tasks significantly faster (an average of 11% faster) and with greater accuracy. However, the benefits were evident only for the more difficult tests.
Researchers suggest that the mechanism involved in achieving greater efficient tissue oxygenation after flavanol intake might be similar to the mechanism of NO2 release that has been detected in the peripheral vasculature. In this study, hypercapnia induced increases in NO release from the vessel endothelium in the cerebral arteries. 9
Dietary strategies that utilize plant-derived flavanols for improving blood oxygenation and cognitive performance may be of benefit to higher risk populations such as smokers, hypertensives, diabetics, and older adults at higher risk for cognitive decline or those with brain disease or injuries. Future research should definitely focus on identifying the populations that could benefit most from these interventions.
Source: Gratton, Gabriele, Samuel R. Weaver, Claire V. Burley, Kathy A. Low, Edward L. Maclin, Paul W. Johns, Quang S. Pham, Samuel JE Lucas, Monica Fabiani, and Catarina Rendeiro. “Dietary flavanols improve cerebral cortical oxygenation and cognition in healthy adults.” Scientific reports 10, no. 1 (2020): 1-13.
© The Author(s) 2020. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License http://creativecommons.org/licenses/by/4.0/
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Posted March 30,2021.
Joyce Smith, BS, is a degreed laboratory technologist. She received her bachelor of arts with a major in Chemistry and a minor in Biology from the University of Saskatchewan and her internship through the University of Saskatchewan College of Medicine and the Royal University Hospital in Saskatoon, Saskatchewan. She currently resides in Bloomingdale, IL.
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