Creatine Monohydrate for Sports & Fitness

Over 40 double-blind or controlled studies have found creatine supplementation (typically 136 mg per pound of body weight per day or 15 to 25 grams per day for five or six days) improves performance of either single or repetitive bouts of short-duration, high-intensity exercise lasting under 30 seconds each.^{1, 2, 3, 4, 5, 6, 7} Examples of this type of exercise include weightlifting; sprinting by runners, cyclists, or swimmers; and many types of athletic training regimens for speed and power. About 15 studies did not report enhancement by creatine of this type of performance. These have been criticized for their small size and other research design problems, but it is possible that some people, especially elite athletes, are less likely to benefit greatly from creatine supplementation.⁸

Long-term use of creatine supplementation is typically done using smaller daily amounts (2 to 5 grams per day) after an initial loading period of several days with 20 grams per day. Very little research has been done to investigate the exercise performance effects of long-term creatine supplementation. One study reported that long-term creatine supplementation improved sprint performance.⁹ Four controlled long-term trials using untrained women,¹⁰ trained men,¹¹ or untrained older adults found that creatine improved gains made in strength and lean body mass from weight-training programs.^{12, 13} However, two controlled trials found no advantage of long-term creatine supplementation in weight-training football players.^{14, 15}

Little is known about long-term side effects of creatine, but no consistent toxicity has been reported in studies of creatine supplementation. In a study of side effects of creatine, diarrhea was the most commonly reported adverse effect of creatine supplementation, followed by muscle cramping.¹⁶ Some reports showed that kidney, liver, and blood functions were not affected by short-term higher amounts^{17, 18} or long-term lower amounts ^{19, 20} of creatine supplementation in healthy young adults. In a small study of people taking 5–30 grams per day, no change in kidney function appeared after up to five years of supplementation.²¹ However, interstitial nephritis, a serious kidney condition, developed in an otherwise healthy young man, supplementing with 20 grams of creatine per day.²² Improvement in kidney function followed avoidance of creatine. Details of this case strongly suggest that creatine supplementation triggered this case of kidney disease. Creatine supplementation may also be dangerous for people with existing kidney disease. In one report, a patient with nephrotic syndrome (a kidney disorder) developed glomerulosclerosis (another serious kidney condition) while taking creatine. when the creatine was discontinued, the glomerulosclerosis resolved.²³

Muscle cramping after creatine supplementation has been anecdotally reported in three studies.^{24, 25, 26}

Creatine is produced naturally in the human liver, pancreas, and kidneys. It is concentrated primarily in muscle tissues, including the heart. Animal proteins, including fish, are the main source of the 1–2 grams per day of dietary creatine most people consume. Supplements in the form of creatine monohydrate are well absorbed and tolerated by the stomach.