Efficacy and safety of ingredients found in preworkout supplements.

Purpose: Published evidence on common ingredients of "energy drinks" and other dietary supplements widely used by consumers in hopes of enhancing athletic performance is reviewed.

Summary: Preworkout products- unregulated dietary supplements- typically contain "proprietary blends" of multiple ingredients, including caffeine, dimethylamylamine, creatine, arginine, β-alanine, taurine, and phosphates. While some dietary supplement labels instruct consumers to seek the advice of a health care professional before using the products, the labels usually do not disclose all ingredients or their precise amounts, and evidence to support the purported performance-enhancing benefits is generally lacking.