Biological confusion, long-standing rumours and practical misuse fuel beliefs about the dangers of creatine.
Creatine vs. Creatinine: Fact or Fiction
There is indeed some biological confusion between creatine and creatinine. As mentioned earlier, creatine is metabolised into creatinine, a biological marker used to assess kidney function. Healthy kidneys are able to filter out creatinine, thereby preventing any overload. The amount of creatinine in the blood is linked to muscle mass, the amount of creatine-rich foods consumed and, of course, supplementation. Consequently, blood and urinary creatinine levels may be temporarily elevated. However, in healthy individuals, current scientific evidence does not indicate any renal toxicity at standard supplementation doses (3 to 5g/day). On the other hand, caution is advised in cases of pre-existing kidney disease, as studies are more limited for these populations (4). Medical advice is strongly recommended if in doubt.
Is there a risk of kidney failure associated with creatine?
The misconception that the kidneys are ‘forced’ to excrete higher-than-normal levels of creatine or creatinine when taking supplements, leading to kidney damage and/or kidney dysfunction, is very widespread. In reality, transient increases in creatine or creatinine levels in the blood or urine due to creatine intake are unlikely to reflect a decline in kidney function. In a review of the literature assessing the safety of creatine (5), the authors found no increase in serum creatinine in 12 studies; 8 studies showed an increase that remained within the normal range; and only 2 studies showed an increase above normal limits following creatine supplementation.
CONCLUSION: Scientific literature indicates that creatine supplementation, when taken at the recommended doses, does not cause kidney damage and/or kidney dysfunction in healthy individuals (4).
Is creatine a performance-enhancing drug?
Creatine is not included on the list of prohibited doping substances defined by the World Anti-Doping Agency. It is sold as a “food supplement”, the marketing, labelling and use of which are strictly regulated by French law. It is also authorised by sports federations, at the recommended daily doses. However, caution is advised in certain cases:
Online purchases from little-known websites may feature ingredient lists that are unclear or incomplete: recommendations vary from one country to another, and certain ingredients may not be listed on the label.
Multi-ingredient products: When a product contains too many active ingredients, there may be interactions between them (inhibition or activation), which can cause adverse effects. It is better to opt for pure creatine.
Supply chain quality and traceability: These two criteria should be of paramount importance when choosing dietary supplements.
What are the possible side effects of creatine?
Below is a non-exhaustive list of adverse effects mentioned in the scientific literature (4):
Water retention: It appears that the most common side effect of creatine supplementation is water retention during the first few days. This is thought to be because creatine is absorbed into the muscle via the bloodstream by a sodium-dependent transporter. As the muscle absorbs creatine, it also absorbs a certain amount of water in order to maintain intracellular osmolality. However, the activity of sodium-potassium pumps will quickly restore this balance. Therefore, if this water retention does occur, it will be short-lived. It should be borne in mind that creatine’s hygroscopic properties, by increasing intracellular water content, help to improve muscle function and recovery, which is why it is recommended (1).
Gastrointestinal disturbances: Bloating and diarrhoea may occasionally occur with creatine doses exceeding 10 g per day, i.e. above the official recommendations. The quality of the product may also have an impact on the bowel movements.
Cramps and dehydration: Creatine, as an active osmotic substance, is thought to preferentially increase the absorption and retention of intracellular water, particularly in the short term. If dehydration or the sensation of cramps are experienced, these may be attributable to other factors: lack of hydration before and during exercise, heavy sweating due to physical exertion, or training in a hot environment. Experimental and clinical research therefore does not appear to support the claim that creatine supplementation causes dehydration and muscle cramps.
What risk factors are associated with creatine use?
Like any dietary supplement, taking creatine is not without risk and must be done in accordance with health guidelines.
Overdose: An overdose can lead to digestive problems.
Combining active substances: In preparation for intensive training or a competition, athletes may be tempted to combine supplements. The combined use of creatine and caffeine, in particular, has attracted the interest of athletes and scientists. The result is that the effect on physical performance has not been significant, whilst the occurrence of gastrointestinal problems is possible, which indirectly interferes with performance (6).
Product purity: When purity and traceability of batches are stated on the labels, this dispels any uncertainty regarding the risks associated with using the product. Indeed, this confirms that the product you are about to consume has undergone rigorous testing, is free from contaminants, and has been certified as compliant. A pure product, free from additives or sweeteners, is always preferable.
Form used: Creatine monohydrate is the most widely studied form of creatine and, as such, the safest. Creatine nitrate, creatine malate, creatine citrate and creatine pyruvate are also available, but these do not benefit from the same track record or the same number of scientific studies as creatine monohydrate.
Does the loading phase increase the risk of side effects?
A creatine “loading phase” is defined as oral supplementation over 5 to 7 days with a dose of 20 to 25 g of creatine per day, often divided into smaller doses throughout the day.
CONCLUSION: This loading dose does indeed increase the incidence of gastrointestinal disturbances when taken at more than 10 g per day. It should be noted that a lower daily dose of creatine (3 to 5 g/day) has been shown to increase intramuscular creatine stores and achieve similar levels of skeletal muscle saturation to the loading dose (4).
Is creatine dangerous for women?
Creatine appears to be beneficial for women’s health at various stages of their lives. However, further scientific research is still needed in this area.
During pregnancy: Creatine is thought to play a role in the stages of reproduction: fertilisation, pregnancy, foetal growth, labour, birth and breastfeeding. Studies have focused in particular on its potential role in preventing high-risk pregnancies, although to date there is no evidence from randomised controlled clinical trials. Furthermore, the safety and tolerability of creatine during pregnancy have not yet been properly established. (8)(9)
As menopause approaches: The effects of creatine are well known in terms of preserving muscle mass and strength, bone health, fatigue, cognitive function and mood, but mainly in men! These are, however, key factors to restore during the perimenopausal period, yet to date, no research has directly assessed the effects of creatine supplementation in perimenopausal women. (9)
On mental health: Emerging evidence suggests that creatine is a promising solution for improving sleep and mental health issues, which are often linked to the hormonal fluctuations women experience throughout their lives. (9)
Due to the wide variability of the menstrual cycle, the use of hormonal contraceptives, hormonal fluctuations during pregnancy and perimenopause, and a likely insufficient intake of dietary creatine, it is essential that future research explores the impact of these life stages on creatine metabolism in women. Research into its tolerability is also required.
