Why Is Creatine Bad for You?

Creatine supplementation can be useful for athletes, but it's not for everyone. As many as 30% of people do not respond to creatine supplementation. Creatine can adversely affect kidney function, so people with kidney disease should speak with their doctor first.

Creatine is a naturally occurring substance derived from three amino acids (methionine, glycine, and arginine) and it is one of the most popular nutritional supplements used for performance enhancement. It is not prohibited by the World Anti-Doping Agency (WADA).

Creatine has been shown to be effective for: 

• Improving training and performance of short-duration, high-intensity exercise 
• Improving strength and power
• Improving anaerobic and aerobic exercise measures
• Enhancing recovery

Creatine supplementation may be useful for athletes in sports that involve short intervals of high-intensity effort followed by brief recovery periods, such as American football, racquet sports, rugby, and other team sports.

Creatine supplementation may be useful for athletes in sports that involve short intervals of high-intensity effort followed by brief recovery periods, such as American football, racquet sports, rugby, and other team sports.

• Up to 30% of people do not respond to creatine supplementation.
• There are claims that creatine can adversely affect kidney function, but current evidence suggests this is not the case in patients with normal kidney function. However, creatine does increase blood levels of creatinine, which is often a marker of reduced kidney function. People who have underlying kidney disease should talk to their doctors before taking any creatine supplementation. 

The potential long-term effects of creatine supplementation are also not known, and the American College of Sports Medicine (ACSM) recommends it be used only by physically mature, well-developed athletes. It is not recommended for use in adolescents. 

However, creatine is generally well-tolerated and side effects are uncommon. Side effects of acute creatine ingestion include: 

• Weight gain (from increased water retention)
• Reduced joint mobility

Other reported side effects may include:

• Muscle cramping
• Nausea
• Gastrointestinal (GI) upset
• Headaches