Creatine, a common component of many sports supplements, has a reputation for causing gastrointestinal distress. Taken properly, however, it should not result in diarrhea.
Creatine occurs naturally in the human body and is present in some foods, such as seafood and beef, notes the U.S. National Library of Medicine. It is also a laboratory-created chemical that is found in most sports supplements sold in the U.S. and is popular with athletes, particularly those engaged in high-intensity sports.
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Some people take supplements to increase creatine in situations when the body does not make enough on its own and to offset age-related muscle loss.
A November 2017 meta-analysis published in the Open Access Journal of Sports Medicine evaluated 22 studies that included more than 700 people. Most study participants were older than 50, an age at which both strength and lean muscle mass begin to sharply decline. Study participants did resistance training two or three times a week while taking either a creatine supplement or a placebo.
In tests of chest press strength and leg press strength, those who took creatine supplements achieved greater gains in both upper and lower body strength than those who did not take creatine supplements.
Read more: Is Creatine Bad for You?
The Myth of Side Effects
While most of the studies in that meta-analysis did not record any major side effects, four studies reported that some participants experienced gastrointestinal distress. None of the participants withdrew from the studies.
In addition to the risk of diarrhea, creatine use has been anecdotally linked to other ailments, such as cramping, dehydration, musculoskeletal injury and kidney problems, according to a review of the literature on the role and safety of creatine published in June 2017 in the Journal of the International Society of Sports Nutrition (ISSN). The review was done, according to the ISSN, to update its stance on the supplement. The only side effect consistently reported in the literature is weight gain, the society says.
However, the ISSN found in its review that athletes who supplement with creatine experience less injury than those who do not and that creatine's water-attracting (osmotic) properties may help athletes stay hydrated and increase their ability to tolerate working out in hot weather.
"We all have a store of creatine in our muscles that helps supply our muscles with energy, called ATP," says Will Bulsiewicz, MD, a gastroenterologist in Mount Pleasant, South Carolina. "People who regularly consume creatine find they store more water in their muscles, provided they are hydrating adequately."
It is this osmotic attribute of creatine, though, that can lead to gastrointestinal distress. Creatine draws water into whatever space it occupies — muscles, but also the bowel.
"If you take creatine as directed, you really should not have creatine-associated diarrhea," Dr. Bulsiewicz says. "The problem occurs when people load up on creatine. Often, when they are just starting a regimen of creatine supplementation, people will take up to four times the amount indicated. That excessive bolus of creatine draws water into the intestine and can cause diarrhea."
Short-term creatine-related diarrhea should not be a big problem. However, if you have diarrhea that lasts for more than two days without improvement, you should seek medical attention, according to the Mayo Clinic. To help ease symptoms and cope with diarrhea, the Mayo Clinic recommends drinking clear liquids such as water, broth and juice, as well as avoiding foods that can make diarrhea worse, such as high-fat, high-fiber and very seasoned foods.
What's a Safe Dose of Creatine?
It is not uncommon for people to use a larger than usual dose, or loading dose, initially.
Research studying creatine to enhance athletic performance, to increase muscle strength and to offset age-related muscle loss describes regimens of short-term loading doses, usually about 20 grams for five to seven days, followed by longer-term maintenance doses, from two to 10 grams.
According to the ISSN study, the fastest way to increase muscular creatine stores may be to consume about 0.3 grams per kilogram of body weight per day for five to seven days, followed by a maintenance dose of three to five grams per day.
For people who are concerned about the risk of gastrointestinal distress, the ISSN states that starting out with the maintenance dose, three to five grams per day, will increase muscular creatine stores in three to four weeks, though the society notes that there is less support for the effect this supplementation dosage will have on performance.
- U.S. National Library of Medicine: “Creatine”
- Open Access Journal of Sports Medicine: “Effect of Creatine Supplementation on Lean Tissue Mass and Muscular Strength in Older Adults: a Meta-Analysis”
- Journal of the International Society of Sports Nutrition: “International Society of Sports Nutrition Position Stand: Safety and Efficacy of Creatine Supplementation in Exercise, Sport and Medicine”
- Will Bulsiewicz, MD, gastroenterologist, Mount Pleasant, South Carolina
- Mayo Clinic: Symptoms Diarrhea: When to See a Doctor"
- Mayo Clinic: "Diarrhea - Diagnosis and Treatment"
Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.