Judging by the outcome of a small clinical trial, cocoa's uncommon antioxidants may boost brain and eye function ... at least for a few hours.
If confirmed in larger, tighter trials, these short-term gains may join the growing list of health benefits attributed to cocoa's polyphenols.
And there's sound reason to believe they would, since these apparent benefits probably flow from cocoa's documented ability to enhance blood flow.
The story began five years ago, when a small clinical study from Britain showed that “raw” cocoa increased blood flow to the gray matter in people's brains (Francis ST et al. 2006).
Cocoa's uncommon antioxidants
This small British study focused on the uncommon polyphenol-class antioxidants in cocoa, called flavanols (catechins) and procyanidins (Field DT et al. 2011).
Flavanols are the building blocks for proanthocyanidins (e.g., OPC/pycnogenol), which abound in grapes, red wine, and a few other foods and herbs.
Though spelled almost the same, flavanols are distinct from flavonols (e.g., quercetin and rutin), which abound in tea, onions, citrus fruits, and many other plant foods.
Flavanols also occur abundantly in green tea – with much smaller concentrations in other plant foods – while procyanidins abound in berries.
By “raw” cocoa, we mean the kind not treated with alkali (Dutched), hence still rich in flavanol-type polyphenols. (Most dark chocolate is made with raw, non-Dutched cocoa, but most cocoa powder is Dutched, hence very low in flavanols.)
The tale continued last year, when Australian scientists reported that subjects who drank either of two cocoa beverages with substantial amounts of flavanols (520 to 994 mg) performed better on tests for anxiety, “cognitive demand” and mental fatigue, compared with a flavanol-free “control” cocoa drink (Scholey AB et al. 2010).
As the Aussies wrote, “This is the first report of acute cognitive improvements following CF [cocoa flavanol] consumption in healthy adults.”
They seemed on the mark when they hypothesized, “While the mechanisms underlying the effects are unknown they may be related to known effects of CF [cocoa flavanols] on endothelial [artery wall] function and blood flow.” (Scholey AB et al. 2010)
Now researchers from the UK's University of Reading report that consumption of dark, flavanol-rich chocolate may improve aspects of eye and brain function.
British pilot trial sees short-term brain, eye boost
The authors of the new study say their findings show that some aspects of vision and cognitive performance in healthy young adults were improved by cocoa containing its natural flavanols (Field DT et al. 2011).
Like the Aussies, they suspect that these effects may be explained by increased cerebral and retinal blood flow caused by cocoa flavanols.
This was a randomized, single-blinded, crossover trial, involving 30 healthy adults aged between 18 and 25.
One group consumed 35 grams of dark chocolate while people in a control group ate the same quantity of white (flavanol-free) chocolate. After a one-week interval between two testing sessions, the groups switched regimens.
The researchers were “blinded” as to which of the two types of chocolate each test group consumed … but the participants knew (by the light or dark color of the chocolate) which of the two kinds they had eaten.
The authors conceded the participants “may conceivably have been influenced by this knowledge.” (Field DT et al. 2011)
The participants were tested for “visual contrast sensitivity”, “motion sensitivity” and cognitive performance (visual-spatial working memory and a sophisticated reaction time task).
Compared with the control group, the dark chocolate group showed improved visual contrast sensitivity and reduced time required to detect motion direction.
As the Brits wrote, “A reduction in the time required to integrate visual motion could be beneficial in time critical everyday tasks, such as driving. The effect on the simpler early phase of the choice reaction time task suggests that CF [cocoa flavanols] can increase response speed in simple tasks.” (Field DT et al. 2011)
The researchers are conducting a follow-up study in older adults.
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