Dark chocolate containing 70 percent cocoa was associated with a blunting in oxidative stress after exercise, measured as a reduction in levels of a compound called F2-isoprostane, according to findings published in European Journal of Nutrition.
“We believe that the small effects observed here could be physiologically important, but arise from cocoa-induced metabolic changes leading to modulation of the major plasma constituents,” wrote scientists led by Glen Davison from Aberystwyth University in Wales.
“In addition, dark chocolate was effective at blunting the exercise-induced increase in plasma total antioxidant status observed in the other trials, providing support for the idea that the elevated total antioxidant status on the dark chocolate trial has physiological significance.”
Oxygen-breathing organisms naturally produce reactive oxygen species (ROS), which play an important role in a range of functions, including cell signalling. However, over production of these ROS from smoking, pollution, sunlight, high intensity exercise, or simply ageing, may overwhelm the body’s antioxidant defences and lead to oxidative stress.
Oxidative stress has been linked to an increased risk of various diseases including cancer, Alzheimer's, and cardiovascular disease.
The researchers also noted that extended periods of exercise are also often used to model physical stress, and that this may be eased by consumption of a polyphenol-rich dark chocolate.
Choc-full of benefits?
According to their new findings, the effects were seen after only one 100 grams serving of the dark chocolate.
“It is possible, therefore, that greater blunting of oxidative stress responses would be observed with a different timing and/or quantity of dark chocolate ingestion, although this will require further investigation,” wrote the researchers.
The health benefits of polyphenols from cocoa have been gathering increasing column inches in the national media. To date studies have reported potential benefits for cardiovascular health, skin health, and even brain health.
The majority of science into the potential benefits of cocoa have revolved around cardiovascular benefits of the flavanols (also known as flavan-3-ols or catechins), and particularly the monomeric flavanol (-)epicatechin.
Davison and his co-workers recruited 14 healthy men to participate in their study. Volunteers were asked to consume 100 grams of dark chocolate (Nestlé Noir 70 percent), a control bar, or nothing. Two hours later they were required to cycle for 2.5 hours at 60 percent of the maximal oxygen uptake level.
Results showed that intake of the dark chocolate resulted in an increase in antioxidant status before the cycling, and reduced levels of F2-isoprostane one hour after the cycling had finished, compared with the control bar.
Insulin levels were also increased before the trial and after cycling for men who consumed the dark chocolate and this was associated with a “better maintenance of plasma glucose concentration”, added the scientists.
On the other hand, there were no changes in markers of immune response, which is known to be affected by rigorous exercise.
“These results with acute dark chocolate consumption are similar to those observed following 2 weeks of daily dark chocolate ingestion,” wrote the researchers.
The other scientists were affiliated with Loughborough University and the University of Newcastle in the UK, and the Nestle Research Center in Lausanne, Switzerland. The study was funded by the Nestle Research Center.
Source: European Journal of Nutrition
Published online ahead of print, doi:
“The effect of acute pre-exercise dark chocolate consumption on plasma antioxidant status, oxidative stress and immunoendocrine responses to prolonged exercise”
Authors: G. Davison, R. Callister, G. Williamson, K.A. Cooper, M. Gleeson