Creatine

(creatine monohydrate) is used in muscle tissue for the production of phosphocreatine, a factor in the formation of ATP, the source of energy for muscle contraction and many other functions in the body. Creatine supplementation increases phosphocreatine levels in muscle, especially when accompanied by exercise or carbohydrate intake. It may also increase exercise-related gains in lean body mass, though it is unclear how much of these gains represents added muscle tissue and how much is simply water retention.

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. 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.

Fewer studies have investigated whether creatine supplementation benefits continuous high-intensity exercise lasting 30 seconds or longer. Five controlled studies have found creatine beneficial for this type of exercise, but one study found no benefit on performance of a military obstacle course run. Most studies of endurance performance have found no advantage of creatine supplementation, except perhaps for non-weight bearing exercise such as cycling.

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. Four controlled long-term trials using untrained women, trained men, or untrained older adults found that creatine improved gains made in strength and lean body mass from weight-training programs. However, two controlled trials found no advantage of long-term creatine supplementation in weight-training football players.

Creatine supplementation appears to increase body weight and lean body mass or fat-free mass, but these measurements do not distinguish between muscle growth and increased water content of muscle. A few double-blind studies using more specific muscle measurements have been done and found that combining creatine supplementation with strength training over several weeks does produce greater increases in muscle size compared with strength training alone. Less.

In a double-blind study, people with COPD received or a placebo for 12 weeks. After the first 2 weeks of supplementation, all participants underwent an outpatient pulmonary rehabilitation program. Compared with the placebo, creatine significantly increased muscle strength, muscle endurance, and overall health status, but not exercise capacity. The amount of creatine used in this study was 5 grams three times a day for 2 weeks, and then 5 grams once a day for 10 weeks. Less.

A double-blind trial found that a supplement of 5 grams of plus 1 gram of glucose taken four times per day for five days followed by twice a day for 51 days significantly lowered serum total triglycerides in both men and women. However, another double-blind trial found no change in any of these blood levels in trained athletes using creatine during a 12-week strength training program. Creatine supplementation in this negative trial was lower—only five grams per day was taken for the last 11 weeks of the study. Less.