Results of a stress test after subjecting study participants to a mock job interview and a mental arithmetic task in front of an audience indicated that consumption of dark chocolate blunted increases in cortisol and epinephrine.
Scientists from the University of Bern and the University of Zurich report their findings in the Journal of the American College of Cardiology.
Food giants like Nestle are known to be researching this field, and scientists from the Swiss company have already published several papers on this topic. A 2009 study published in the Journal of Proteome Research indicated that consuming 40 g of dark chocolate per day for two weeks led to reductions in the stress hormone cortisol and catecholamines.
Barry Callebaut have also funded studies in this area, with results of a 2013 randomized, double-blind study by scientists from the Swinburne University of Technology in Australia indicating that cocoa flavanols may keep you calmer and content without affecting cognitive performance (Journal of Psychopharmacology, Vol. 27, pp. 451-458).
The benefits are linked to the flavanols in cocoa, a class of polyphenols, and particularly the monomeric flavanol (-) epicatechin.
According to a 2003 analysis by the US Department of Agriculture (USDA), a typical 100 g bar of dark chocolate contains 41.50 mg of epicatechin and 11.99 mg of catechin. The same amount of milk chocolate contains an average of 10.45 mg of epicatechin and 2.90 mg of catechin.
For the new Swiss study, scientists led by Petra Wirtz used the commercial dark chocolate “Noir 72%” (Chocolat Frey AG, Buchs AG) which contained 125mg of epicatechin per 50 gram serving. Dr Wirtz and her co-workers recruited 65 healthy men aged between 20 and 50 to participate in their study. The men were randomly assigned to receive either dark chocolate or placebo two hours before the stress test.
Results showed that markers of stress increased across both groups, but the dark chocolate group showed blunted responses for cortisol and epinephrine, showing a peripheral effect. No changes were observed for central nervous system markers, such as ACTH and norepinephrine.
“Our findings indicate that acute flavonoid-rich dark chocolate intake buffers endocrine stress reactivity on the level of the adrenal gland suggesting a peripheral stress-protective effect of dark chocolate consumption, particularly, since in the chocolate group the unaffected ACTH stress response did not result in correspondingly high cortisol secretion,” wrote the researchers.
“While it is unclear whether epicatechin can access the human brain at levels sufficiently high to modify central nervous processes, inhibitory peripheral effects of dietary flavonoids on the biosynthesis and secretion of cortisol and catecholamines seem plausible.”
The study was funded by the Swiss Cocoa and Chocolate Foundation and the Swiss National Science Foundation.
Source: Journal of the American College of Cardiology
Published online ahead of print, doi: 10.1016/j.jacc.2014.02.580
“Dark chocolate intake buffers stress reactivity in humans”
Authors: P.H. Wirtz, R. von Känel, R. Meister, et al