Six-week oral guanidinoacetic acid administration improves muscular performance in healthy volunteers

Background Guanidinoacetic acid (GAA), a natural precursor of creatine, is a new promising dietary supplement, yet its performance-enhancing effect, if any, has yet to be established. The purpose of this pilot study was to evaluate the effects of supplemental GAA on muscle strength, anaerobic performance, and aerobic performance in healthy men and women. Method The study enrolled 48 young participants (age, 22.3 ± 1.5 years; height, 176.4 ± 10.0 cm; weight, 71.9 ± 14.3 kg), who received oral doses of GAA (1.2, 2.4, or 4.8 g/d) for 6 weeks in a randomized, double-blind, placebo-controlled trials. Results Significant differences were observed between treatment groups for handgrip strength among participants receiving 1.2 g of GAA per day and 2.4 g of GAA per day, as compared with placebo (P < 0.05). In addition, muscle endurance expressed as the change from baseline in repetitions performed in the bench press exercise was significantly greater in the 1.2 g/d dose of GAA (P = 0.01) and the 4.8 g/d dose (P = 0.01) compared with placebo. No dose-response differences were found between trials. Conclusions Results from this preliminary study indicate that supplemental GAA ingested in young individuals can improve exercise performance, even at low doses (1.2 g/d).