RESUMO
Purpose: To investigate the effects of hydrolyzed whey protein enriched with glutamine dipeptide on the percentage of oxygen consumption, second ventilatory threshold, duration and total distance covered, and skeletal muscle damage during an exhaustion test in elite triathletes. Methods: The study was a randomized, double-blinded, placebo-controlled, crossover trial. Nine male triathletes performed a progressive incremental test on a treadmill ergometer (1.4â km h-1·3â min-1) 30â min after ingesting either 50â g of maltodextrin plus four tablets of 700â mg hydrolyzed whey protein enriched with 175â mg of glutamine dipeptide diluted in 250â ml of water (MGln) or four tablets of 700â mg maltodextrin plus 50â g maltodextrin diluted in 250â ml of water (M). Each athlete was submitted to the two dietary treatments and two corresponding exhaustive physical tests with an interval of one week between the interventions. The effects of the two treatments were then compared within the same athlete. Maximal oxygen consumption, percentage of maximal oxygen consumption, second ventilatory threshold, and duration and total distance covered were measured during the exhaustion test. Blood was collected before and immediately after the test for the determination of plasma lactate dehydrogenase (LDH) and creatine kinase (CK) activities and lactate concentration (also measured 6, 10, and 15â min after the test). Plasma cytokines (IL-6, IL-1ß, TNF-α, IL-8, IL-10, and IL-1ra) and C-reactive protein levels were also measured. Results: A single dose of MGln increased the percentage of maximal oxygen consumption, second ventilatory threshold duration, and total distance covered during the exhaustion test and augmented plasma lactate levels 6 and 15â min after the test. MGln also decreased plasma LDH and CK activities indicating muscle damage protection. Plasma cytokine and C-reactive protein levels did not change across the study periods. Conclusion: Conditions including overnight fasting and a single dose of MGln supplementation resulted in exercising at a higher percentage of maximal oxygen consumption, a higher second ventilatory threshold, blood lactate levels, and reductions in plasma markers of muscle damage during an exhaustion test in elite triathletes. These findings support oral glutamine supplementation's efficacy in triathletes, but further studies require.
RESUMO
The presence of performance-enhancing drugs in dietary supplements poses serious anti-doping and health risks to athletes and military service members. A positive drug test, suboptimal health, or adverse event can ruin a career in either setting. These populations need to be certain in advance that a product is of high quality and free from performance-enhancing drugs and other banned substances. However, no regulatory authority conducts or mandates a quality review before dietary supplements are sold. Under the Food Drug and Cosmetic Act, the Food and Drug Administration does not have a role in the premarket safety review of dietary supplements. Due to the increasing demand for high-quality, properly labeled dietary supplements, multiple companies have stepped into this void by offering testing and quality review programs for dietary supplements. Each of these third-party programs has its own quality assurance program with varying testing components. It is difficult for consumers in the sport and military settings to assess whether a particular certification program reduces the risks enough so that they can use a product with confidence. This article puts forward the consensus of the authors on current best practices for third-party certification programs for dietary supplements consumed by athletes and military service members. Also discussed are important ways that third-party programs can develop in the future to improve access to safe, high-quality dietary supplements for these populations.