Creatine, or methyl guanidine-acetic acid, is an amino acid naturally produced by the body and located in muscle cells. About 95 percent is situated in and around the skeletal muscles. Creatine supplements have few and relatively rare side effects, but many users have reported anger and mood swings, which disappear when they stop taking the supplements.
Besides occurring naturally in the body, creatine is obtained through diet, mainly by eating meat and fish. The best sources of creatine are herring, salmon, tuna, pork and beef. People can also purchase creatine tablets, powder, and energy drinks and bars at pharmacies, grocery stores and online retail stores. Bodybuilders, athletes and many people working on physical fitness begin taking creatine supplements because the substance quickly increases body mass and lean muscle formation.
Physical Side Effects
Although creatine is a natural amino acid rather than a hormonal supplement or anabolic steroid prescription drug, it still can cause side effects. The most common are stomach aches and nausea when a person initially begins taking creatine. People also may need to urinate more frequently than usual. Creatine users have greater potential to develop kidney stones. In addition, because creatine causes muscles to develop more rapidly than the supporting tendons, this can mean higher susceptibility to tendon tears and other injuries during sports.
Mental Side Effects
Some creatine users have reported in online reviews and message boards their experience of increased mood swings, anger, anxiety, panic attacks, depression, nightmares and aggression. Some say they have stopped taking creatine supplements because of the negative emotional effects.
Two particular issues seem to worsen the anger side effects of creatine. Not drinking enough water while taking the supplement can exacerbate a mood disorder such as depression or bipolar disorder, and that lack of hydration also can interfere with mood disorder medications. Creatine users should be certain to stay hydrated during their workouts. In addition, taking large amounts of the supplement sometimes causes more problems with anger side effects. This is more common during the "loading phase," an optional high-powered start to creatine supplementation which involves taking 20 to 30 grams a day divided into 3 or 4 doses. The regular dose is 2 to 5 grams a day. People doing creatine loading sometimes experience paranoia and anger-related behaviors.
No athletic regulatory agencies specifically ban creatine supplements, but some do address the issue in a roundabout way. The International Olympic Committee, for instance, has an umbrella clause prohibiting ergogenic aids, which would include creatine, as that substance has been shown to enhance athletic performance. The problem with enforcement is no test can definitively prove creatine supplementation.