Why do athletes and bodybuilders use dietary supplements? Many athletes and bodybuilders turn to supplements in hopes of enhancing strength, endurance, and muscle size. Despite these goals, several of these products include potentially harmful substances. Additionally, some supplements like glutamine, choline, methoxyisoflavone, quercetin, zinc/magnesium aspartate, nitric oxide, and L-arginine have not been convincingly shown to boost physical performance. Which supplements are prohibited by