Athletes consume an extra of nutritional supplements every day with the purpose of improving their athletic performance, sometimes without being aware of their health. Cocoa could be a good nutritional supplement for athletes without causing them adverse effects. One of the most common health concerns in athletes are gastrointestinal problems. The cause of these problems seem to be a compendium of physiological and mechanical causes that are altered due to nutritional factors. Currently, there is no assay in which a nutritional intervention study has been proposed over time of training, in order to improve the gastrointestinal problems associated with the performance of physical exercise.

The objective of this project is to investigate the benefits of daily consumption of cocoa in endurance athletes in:

A) Gastrointestinal problems associated with exercise. B) Reinforcement of the gastrointestinal barrier. C) Parameters of inflammation and oxidative stress. D) Sports performance. E) Body composition

The starting hypothesis of this project is based on the fact that daily cocoa consumption could improve the gastrointestinal symptoms associated with resistance exercise. Cocoa decreases the symptoms associated with splenic hypovolemia and strengthens the gastrointestinal epithelial barrier increasing the presence of Lactobacillus spp. and Bifidobacterium spp. in the intestinal microbiota.

A randomized, blinded, parallel placebo controlled intervention study will be carried out in endurance athletes who train in the sports facilities of the European University of Madrid. The number of male athletes for the study will be 56 (28 in each experimental group), all of them aimed at competition with an age between 18 and 40 years and an aerobic power consumption of oxygen greater than or equal to 55 mL / kg / min). The calculation of the sample size has been made selecting with a significance level alpha = 0.05 and a power (beta) of 0.90 for a 2-tailed analysis, taking into account we want to detect a difference of at least 15% in the improvement of the gastrointestinal symptoms, that the standard detected deviation in the questionnaire to be used, in previous studies, is 1.5 points out of 9 and that the expected proportion of losses is 15%.

Before and after the intervention, the athletes will do a test in which we will measure their maximum aerobic capacity. This will be done in the facilities of Europea University of Madrid where there is available a rolling belt. Also, they will do a second test in which we will measure the time they spend running a kilometer at the maximum speed. Body composition will be evaluated by dual-energy X-ray absorptiometry (DEXA). Blood, urine and feces samples will be required before and after the physical tests. Blood and urine samples will be collected in the morning while the feces samples will be collected the day before. The biological samples will be frozen at -80ºC until analyses.

The intervention will be carried out for 10 weeks. Cocoa or placebo will be provide in a single daily intake of 5 g of cocoa containing 500 mg of flavanols (dose at which a prebiotic effect has been demonstrated) or 5 g of maltodextrin.

Inclusion Criteria:

• Men.
• Age between 18 and 50 years
• Aerobic power of oxygen consumption greater than or equal to 55 mL / kg / min

Exclusion Criteria:

• Intake of antibiotics (3 months before the trial) or any chronical medication.
• Intake of probiotics, prebiotics or any type of food or ergogenic supplements.
• To be vegetarian or vegan
• Smoke.
• Have documented gastrointestinal diseases (ulcers, irritable bowel, ulcerative colitis, Crohn's disease, etc.).
• Previous gastrointestinal surgeries or any disease diagnosed at the time of inclusion in the study

High performance sportsmen

Cocoa and maltodextrin (placebo) are provided in identical sachets which are identified just with the letters A and B.