Creatine dangers and side effects: what does science say?

Creatine is an amino acid naturally present in our bodies and in certain foods, such as meat and fish. Used as a supplement, it is valued for improving physical performance, increasing muscle mass, and supporting recovery.

However, its image is sometimes tarnished by rumors concerning serious side effects, particularly on kidney function.

So, is creatine really dangerous, or are these fears based on misunderstandings? Let's review what the studies say.

The most frequent side effects

In some individuals, creatine intake can cause mild and transient discomfort:

• Intramuscular water retention: linked to the saturation of muscles with creatine phosphate. This can lead to a weight gain of 1 to 2 kg, without an increase in fat mass.
• Digestive issues: cramps or discomfort, often related to excessively high doses taken at once. Splitting doses or reducing the daily amount can limit these effects.
• Muscle cramps: although reported by some users, scientific studies do not confirm a direct link.

The question of kidneys and renal function

The main concern surrounding creatine relates to kidney problems.

The fears stem from the fact that supplementation increases blood creatinine levels, a marker typically used to assess kidney health. However, this increase does not necessarily reflect a deterioration in kidney function, but rather a mechanical consequence of creatine consumption.

Numerous long-term studies (up to 5 years of follow-up) show that no kidney function impairment is observed in healthy individuals consuming the recommended dose (3 to 5 g/day).

Conversely, for individuals already suffering from kidney diseases, supplementation should be avoided or medically supervised.

At-risk populations

Certain situations require caution:

• Pregnant or breastfeeding women: lack of sufficient safety data, so supplementation is not recommended without medical advice.
• Individuals with pre-existing kidney disease: mandatory medical monitoring.
• Children and adolescents: possible use in a supervised sports setting, but with professional monitoring.

Creatine: a doping product or not?

Contrary to some misconceptions, creatine is not considered a doping product by the World Anti-Doping Agency (WADA).

It is a legal dietary supplement, whose effects are linked to the natural increase in phosphocreatine reserves in muscles, and not to a hormonal or steroid action.

The benefits that outweigh the risks

By following the dosages validated by scientific literature (3 to 5 g/day), creatine monohydrate proves to be not only safe for the majority of healthy adults but also beneficial for:

• Improving physical performance.
• Promoting muscle mass gain.
• Reducing fatigue during repeated efforts.

In summary

• Real risks: mild digestive effects, water retention, non-pathological increase in creatinine.
• No kidney danger in healthy individuals at recommended doses.
• Precautions: kidney disease, pregnancy, breastfeeding.
• Legal status: not a doping agent.

Scientific sources

• Kreider RB et al. International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation. J Int Soc Sports Nutr. 2017.
• Poortmans JR & Francaux M. Long-term oral creatine supplementation does not impair renal function in healthy athletes. Med Sci Sports Exerc. 1999.
• Branch JD. Effect of creatine supplementation on body composition and performance: a meta-analysis. Int J Sport Nutr Exerc Metab. 2003.