What is it?

Creatine is the most popular nutritional supplement in the United States with approximate annual sales of $400 million. It is not recommended for individuals under 18 years old, given research in safety is lacking in this age group. That said, the reported use is as high as 40% in 11th and 12th graders athletes.

Creatine is produced in the liver and can also be found in our diet through eating meat or fish. In our bodies, approximately 95% is stored in skeletal muscle, while the remainder is stored in brain, testicular and kidney tissues. Creatine is combined with phosphate in our muscles and serves as a readily available source of energy while exercising, especially in the first few minutes of exercise. Studies show variations in how much creatine phosphate stores increase after supplementation, but it is estimated to be in the range of 10-40% in muscle tissue.

How Is It Used?

Various dosing regimens exist, including 3 grams a day for 4 weeks, but others argue for a shorter loading period of 5 grams four times daily over 5-7 days followed by maintenance dosing. Muscle levels can be maintained by continuing supplementation of 2 grams per day, but stores are depleted to pre-supplementation levels about 4 weeks after cessation.

Creatine supplements are available in multiple forms, but the recommended, most studied form is creatine monohydrate. Other forms are more expensive and may contain impurities. It is classified as a supplement and therefore quality and safety is not regulated by the FDA. Also, it is not restricted by the World Anti-Doping Agency (WADA), likely lending to its popularity.

Does It Work?

Creatine has been shown to be effective in improving performance in repeated bouts of short-duration, high-intensity exercise (like weight lifting, jumping and sprinting). Performance improvements are reported to be 5-15% for maximal power and 1-5% in single sprint time. However, it is clear that improvements only come when combined with regular, highintensity training. Approximately 30% of individuals do not increase muscle stores of creatine or have improvements in performance after supplementation. Supplementation likely does not improve performance in endurance activities lasting longer than 2 minutes or prevent muscle soreness. However, there is some evidence supplementation can reduce muscle damage in injured athletes.

What Are the Side Effects?

Side-effects include weight gain through increased water retention, muscle cramps, upset stomach and decrease joint mobility. It appears to be safe for short term use but long term safety evidence is not available currently.

AMSSM Member Authors
Jeremy Johnson, MD and Ronan Cahill, MD

References
Cooper R, Naclerio F, Allgrove J, Jimenez A. Creatine supplementation with specific view to exercise/sports performance: an update. J Int Soc Sports Nutr. 2012;9(1):33. doi:10.1186/1550-2783-9-33.
Kreider RB, Kalman DS, Antonio J, et al. International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine. J Int Soc Sports Nutr. 2017;14(1):18. doi:10.1186/s12970-017-0173-z.