Creatine is an amino acid naturally present in our body 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 studies say.
The most frequent side effects
In some people, taking creatine 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 problems: 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 around creatine relates to kidney problems.
Fears stem from the fact that supplementation increases blood creatinine levels, a marker usually 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 alteration of renal function is observed in healthy individuals consuming the recommended dose (3 to 5 g/day).
However, in people already suffering from kidney disease, supplementation should be avoided or medically supervised.
At-risk populations
Certain situations require caution:
- Pregnant or breastfeeding women: insufficient 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 sporting context, 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 of phosphocreatine reserves in muscles, and not to hormonal or steroid action.
Benefits that outweigh the risks
By following the dosages validated by scientific literature (3 to 5 g/day), creatine monohydrate is 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 people at recommended doses.
- Precautions: kidney disease, pregnancy, breastfeeding.
- Legal status: non-doping.
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.