Creatine (most often in the form of creatine monohydrate) is a popular sports supplement. It’s been widely available since the 1990s and has become so commonplace that it’s now included in many pre- and post-workout products marketed to athletes. Here we’ll look at some of the claims made about it.

What is creatine?

Creatine is a compound that occurs naturally in our bodies. We get some of it from our diet, and our liver and kidneys can also synthesize it from amino acids. It’s stored mostly in our muscles. It has a role to play in short-term energy production; for those who remember a little biochemistry, it facilitates recycling of ADP to ATP in the cells. In layman’s terms, it helps with recovery during short bursts of intense activity.

Does it work?

Creatine is one of the best-researched sports supplements on the market. A review from 2003 suggests that creatine may be helpful for athletes looking to improve strength, speed, and activities involving bursts of activity. A later review from 2012 confirmed this. It appears to have the greatest benefits for increasing maximum strength and power output, as well as improving recovery when performing multiple maximum effort sets. It also appears to have a smaller benefit for anaerobic performance, but no significant effect on aerobic exercise performance.

How much do I need to take to get results?

Most of the studies have used a similar loading protocol of around 20g per day for a short period (around five days), followed by a longer period at a lower dose (typically around 5g per day). Some studies have suggested that it is possible to get a performance-boosting effect at a lower dose, but others have found no effect. The jury is still out.

What are the side effects?

Creatine use has some side effects that athletes should be aware of. It is associated with immediate weight gain—potentially up to a couple of kilograms or more—mostly due to fluid retention inside the muscle cells. It may also lead to increased weight gain in athletes who are doing regular resistance training. This is certainly something to bear in mind if you are competing in a weight class sport or one in which body weight is a significant factor (e.g., running, cycling, climbing), and for some athletes, it may well outweigh any possible benefits.

Media claims and anecdotes have also associated creatine use with muscle cramping, dehydration, liver damage and stomach pain, bloating or diarrhea. There’s little scientific evidence to support these claims; research suggests that those supplementing with creatine are at no greater risk of these symptoms than those not doing so. However, it’s possible that some athletes respond badly to creatine supplements, so it’s unwise to try it for the first time just before an important event. (This should apply to all new supplements or training interventions, of course.)

Safety

There have also been some concerns about more serious health effects of creatine supplementation. Most widespread is the suggestion that it may have a detrimental effect on kidney function. Research focusing on kidney function has found no negative effects in studies lasting up to 12 weeks on healthy adults, but those with existing liver or kidney disorders are usually advised to avoid creatine supplements as a precaution.

There have also been concerns that creatine may increase the risk of certain cancers, especially after a study published in 2015 found a link between the use of certain muscle building supplements, including those containing creatine, and slightly higher rate of testicular cancer in men. This study was based on surveying men about their supplement use, and the limitations of this kind of study mean that it’s hard to draw firm conclusions as to whether creatine is actually risk factor. However, it does suggest that more research in this area would be desirable. While there is no conclusive link between creatine and cancer, it should be noted that there are no long-term studies of the health effects of creatine in athletes.

Your mileage may vary

The effects of creatine supplementation can vary significantly from one person to another. Vegetarians and vegans are one group that might potentially find supplementation more helpful. Creatine is found only in meat and fish, and there are no plant- based sources. (Creatine supplements are manufactured synthetically and are generally suitable for vegans). Although the body can make its own creatine, vegetarians typically have lower levels of creatine in their body than non-vegetarians, and (although research is fairly limited) may benefit more than non-vegetarians from supplementation.

Other studies have found that people respond differently to creatine supplementation, with some showing a much greater increase in creatine levels than others. The proportions of various muscle fiber types may be one factor influencing this.

The verdict: TRUE. Creatine supplementation does appear to have performance-enhancing effects, but it’s worth bearing in mind that not everyone will get the same benefit from it, and that you could also experience side effects. Whether it suits you will depend on your individual response as well as your sport. While it appears to be relatively safe, there’s a lack of research looking at long-term effects.