Cocoa contains a particularly high concentration of flavanols, and in recent years there has been an increasing interest in the health benefits of flavanol-containing foods.
Writing in the journal, Physiology & Behavior, the authors said their findings show that performance on vision tests in healthy young adults and some aspects of cognitive performance can be improved by the acute intake of cocoa flavanols (CF).
Improvements in visual function were observed approximately 2.5 hours after CF consumption, added the team, which is based at Reading University’s School of Psychology and Clinical Language Sciences.
“As well as extending the range of cognitive tasks that are known to be influenced by CF consumption, this is the first report of acute effects of CF on the efficiency of visual function,” note the authors.
They said that intake of CF has previously been shown to influence hemodynamics, increasing both central and peripheral blood flow.
The researchers’ theory is that the acute effects may be explained by increased cerebral blood flow caused by CF, although “in the case of contrast sensitivity there may be an additional contribution from CF induced retinal blood flow changes.”
The study
The authors said the methodology used was a randomized, single-blinded, order counterbalanced, crossover design.
The trial involved 30 healthy adults aged between 18 and 25, consuming both dark chocolate and a matched quantity of white chocolate, with a one week interval between testing sessions.
Each participant was tested in a high CF condition and a low CF condition, reported the team.
In the high CF condition participants consumed 35 g of the commercially available dark chocolate - Choxi+ (manufactured by Prestat), which contained 178 kcal and 773 mg of CF and also contained 38 mg of caffeine and 222 mg of theobromine.
In the control condition participants consumed 35 g of white chocolate (Waitrose own brand), which contained 196 kcal and only trace amounts of CF, caffeine, and theobromine, said the team.
The researchers were blind to which of the two types of chocolate had been consumed but the authors said that participants knew which of the two chocolates they had eaten, and they conceded they “may conceivably have been influenced by this knowledge.”
Cognitive and visual testing began at 11am and lasted approximately 45 minutes, said the authors. “The two hour interval was chosen to coincide the test battery with the peak of the blood flow effects of CF detected in previous work (Francis et al),” they explained.
Visual contrast sensitivity was assessed by reading numbers that became progressively more similar in luminance to their background, said the researchers.
Motion sensitivity was assessed firstly by measuring the threshold proportion of coherently moving signal dots that could be detected against a background of random motion, and also by determining the minimum time required to detect motion direction in a display containing a high proportion of coherent motion.
Cognitive performance was assessed using a visual spatial working memory for location task and a choice reaction time task designed to engage processes of sustained attention and inhibition.
Results
Relative to the control condition, CF improved visual contrast sensitivity and reduced the time required to detect motion direction, reported the team.
“In terms of cognitive performance, CF improved spatial memory and performance on some aspects of the choice reaction time task,” they found.
“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 can increase response speed in simple tasks,” note the authors, when evaluating the value of the findings.
The researchers added that as this initial investigation was only focused on the potential influence of CF on visual function in young adults, they are conducting a follow up study on their findings with older adults.
Source: Physiology & Behavior
Published online ahead of print: doi:10.1016/j.physbeh.2011.02.013
Title: Consumption of cocoa flavanols results in an acute improvement in visual and cognitive functions
Authors: D. T. Field, C. M. Williams, L T. Butler