The team from Belgium’s Vrije Universiteit in Brussels, also found no effect of the cocoa flavanols (CF) on fat breakdown and exercise-induced inflammation.
“Given that CF intake did not reduce time to complete a second time trial, exercise-induced inflammation and lipid peroxidation, a biomarker of oxidative stress, we failed to support the hypothesis that CF intake could enhance post-exercise recovery,” said the team, led by professor Romain Meeusen, in the Journal of the International Society of Sports Nutrition,
Despite these results, an additional finding that acute cocoa flavanol intake increased total antioxidant capacity (TAC) in response to exercise was described as “promising”
TAC refers to the ability to evaluate the antioxidant response against the harmful free radicals produced during intense exercise.
Previous studies have suggested the intake of CF, contained in foods such as dark chocolate, has the capacity to increase TAC and decrease the presence of lipid oxidation products.
This observation has thus formed a scientific reasoning for dark chocolate to be classed as a sports nutrition product although any potential benefits are offset by the additional sugar and calories.
Earlier this year, confectionery giant Mars made available its CocoaVia line of cocoa flavanol-based food supplements in the UK and Ireland.
Meanwhile elite and recreational athletes have pointed to Swiss confectionary specialists Barry Callebaut’s Acticoa blend of high-antioxidant cocoa and chocolate ingredients as a pre and post exercise food to aid performance and recovery.
Professor Meeusen’s trial involved taking 12 well-trained male cyclists and enrolling them in a randomized, double-blind, cross over study.
Subjects then consumed either a high CF-content chocolate milk (CF - 903.75 milligrams (mg) CF) or the placebo low CF chocolate milk (PL – 15 mg CF) which were matched in macronutrients, caffeine and theobromine.
The exact composition of the CF and PL drink, also included monomers (epicatechin, catechin) and oligomeric proanthocyanidins.
As the peak blood concentration of CF is reached 2 hours after consumption of the drink, a second blood sample was taken 100 minutes later. Subsequently, a 30 minute time trial (TT) was started.
Immediately after the TT, a third blood sample was taken. A forth sample was taken after a 100 minutes passive recovery and consequently a second 30-min TT was started. Immediately after the second TT, a fifth blood sample was taken.
The blood sample schedule aimed to assess epicatechin serum concentrations, trolox equivalent antioxidative capacity (TEAC), uric acid (UA), which are considered markers of oxidative stress.
In addition, NO production was indirectly estimated by measuring its substrate L-arginine/ADMA and its by-product citrulline levels.
Plasma markers of inflammation featured in the assessment included levels of interleukin (IL)-1, IL-6 and tumour necrosis factor (TNF)-α in blood plasma.
Results appear to show epicatechin concentrations increased by CF intake, a result echoed by the exercise-induced increase of TEAC/UA that was also improved by CF intake.
However, exercise-induced increases in MDA, IL-1 and IL-6 were not affected by CF intake,
TNF-α was found to be unaltered by exercise and by CF. Exercise-induced decreases in L-arginine/ADMA and increases in citrulline were not affected by CF intake.
Finally, TT1 and TT2 performance along with exercise-induced physiological changes were unaffected by CF intake.
“In this study, time to complete TT1 was not influenced by CF intake, despite the small significant increase in relative power output at the end of TT1,” the study explained.
“Increases in rate of perceived exertion, lactate, heart rate and glucose during TT1 were not affected by CF intake. This suggests that acute CF intake has very limited ergogenic effects in well-trained cyclists.”
The team recommended that future research should focus on its implications on a broader range of biomarkers of oxidative stress, metabolic and vascular parameters in healthy and diseased populations.
Source: Journal of the International Society of Sports Nutrition
Published online ahead of print: doi.org/10.1186/s12970-017-0186-7
“Acute cocoa Flavanols intake has minimal effects on exercise-induced oxidative stress and nitric oxide production in healthy cyclists: a randomized controlled trial.”
Authors: Lieselot Decroix, Cajsa Tonoli, Danusa Dias Soares, Amandine Descat, Marie-José Drittij-Reijnders, Antje Weseler, Aalt Bast, Wilhelm Stahl, Elsa Heyman and Romain Meeusen