Researchers reviewed published and unpublished studies conducted from 1966 through 2005 and identified 12 clinically controlled trials involving 266 people that measured the effects of oral creatine supplements on those with hereditary muscle diseases. The minimum dosage in all the studies was 30 mg of creatine per kilogram of body weight or about 1,500 mg of creatine per day for a person weighing 110 pounds. Researchers found in trials involving 138 participants with muscular dystrophies, those who had taken a creatine supplement had a maximum voluntary muscle contraction 8.5% greater than those who had taken a placebo. Doctors also found that during the treatment period, those in the creatine groups gained an average of 1.4 pounds more lean body mass than did those who had taken a placebo. None of the trials reported any clinically relevant side effects.
The scientists noted in creatine trials including 33 participants with a certain class of muscular dystrophies (metabolic myopathies), there was no significant difference in strength between treatment and placebo groups. In one trial using a high dose of creatine (150 mg of creatine per kilogram of body weight), participants who—because of metabolic myopathies—were unable to convert stored energy (glycogen) into usable energy (glucose) reported a significant increase in muscle pain during the treatment period. The researchers concluded that short- and medium-term treatment with creatine improves muscle strength in people with muscular dystrophies without side effects.