Found naturally in human and animal muscles, creatine also has become a multimillion-dollar seller on the supplement market through promises of building muscles.
And it appears to deliver. A number of large trials have shown creatine supplements helping people build muscle . But that may not be enough to recommend its use, some experts say.
Creatine may work, but "so does ephedra," said Dr. Catherine Ulbricht, editor of Natural Standard, referring to the supplement that could help people with short-term weight loss but was linked to strokes and heart problems and was ultimately banned by the Food and Drug Administration.
"Creatine's safety profile isn't as harsh as ephedra, but it's not something people should just be throwing in their water every day," said Ulbricht, whose company tracks research in alternative and complementary medicine.
How creatine works
Creatine is composed of amino acids attached to a phosphate group, which is what helps the body generate energy.
Cells in the human body normally get energy by breaking down the compound adenosine triphosphate, or ATP. Energy is released when ATP is broken into adenosine diphosphate and a phosphate group. After an ATP molecule has been broken, it can be rebuilt and reused. The presence of creatine allows ATP to be rebuilt quickly, allowing the body to generate more energy quickly.
"It's an immediately available pool of phosphate, essentially," explained Dr. Jon Finnoff, a sports medicine doctor with the Mayo Clinic.
This also helps explain why creatine can help build muscle but doesn't necessarily help with activities like endurance running.
"After 30 seconds, you've used all the phosphates from that creatine, so it no longer gives you any benefit," Finnoff said, adding that it takes two to three minutes for the body to regenerate its supply.
Creatine gained national attention during the summer of 1998, as Mark McGwire of the St. Louis Cardinals and Sammy Sosa of the Chicago Cubs pursued baseball's single-season home run record. McGwire, whose 70 home runs would break a record that had stood for 37 years, admitted he was using the supplement. Sosa, who also broke the record but finished second to McGwire, later admitted using creatine, too.
Of course, many of the muscular sluggers of the 1990s and 2000s took steroids in addition to dietary supplements.
"The people who take creatine are going to have some benefit over those who do not, but they're not dramatic and it's not going to make someone huge, but it does help," Finnoff told MyHealthNewsDaily. "It's not going to make somebody who's skinny and lifts weights huge."
Creatine has been tested for other potential benefits. Trials have been conducted for possible uses against diseases such as amyotrophic lateral sclerosis (also called Lou Gehrig's disease), muscular dystrophy and Huntington's disease, but it has not shown a clear benefit in treatment.
Risks and side effects
While muscle growth remains the main potential benefit of creatine use, it needs to be weighed against potential side effects.
Kidney damage is a primary concern, which is why water needs to be taken with creatine. Other potential side effects include gastrointestinal symptoms, muscle cramps and an effect on insulin in the body .
Because many of creatine's effects are not well known, pregnant and breast-feeding women as well as children are advised against taking it.
"There are certain people who should not use it anyone who uses it should discuss it with their health care provider before they take it," Ulbricht said.
Finnoff echoed those sentiments, but said creatine could be helpful for those who are healthy.
"It would be safe if taken within the recommended doses. There haven't been any studies that have shown problems in a healthy person who is taking it within the recommended doses," he said. In abnormal doses, he added, some of it can be converted by the body into formaldehyde.
The problem then, Finnoff said, is one of regulation.
Because creatine is a dietary supplement, it isn't regulated by the FDA. As a result, questions can arise as to how pure the ingredients are and whether they are present in the amounts claimed on the packaging.
"That's one of the biggest issues with nutritional supplements ," Finnoff said.
He also noted that pharmaceutical companies may manufacture the supplements in the same place as regulated medications, and so the supplements can contain trace amounts of substances a person doesn't want. This can be problematic for someone in a sport with strict drug testing.
Finnoff explained that creatine can be part of a good muscle-gain regimen when taken in 20-gram doses for five days to load the body's stores, and 2- to 5-gram doses in the days following.
But he is reluctant to recommend simply checking the packaging and buying it at a store.
"You don't know whether you're taking creatine when you buy something over the counter," Finnoff said. "I wouldn't recommend someone spend money if they don't know what's in the product."