Source:
http://healthlink.mcw.edu/index.htmlCreatine supplementation has become tremendously popular in recent years; athletes take it to "bulk up" their muscles. Creatine has been claimed to increase muscle strength, and to delay fatigue, allowing athletes to train harder and achieve greater muscle gains beyond normal capacities. Companies promoting creatine supplements also claim that creatine can help burn fat and increase muscle mass. And creatine is claimed to increase strength in the elderly, in people with muscle disease, and in people suffering from heart disease.
Preliminary medical research shows some of these claims to be accurate. But others lack supporting scientific evidence.
What is Creatine?Creatine is found in amino acids (glycine, arginine, and methionine). It is synthesized from these amino acids in the liver, pancreas and kidneys. Muscles take up the majority of the creatine found in the body. It is in the muscle that creatine is converted to phospocreatine, which is necessary for ATP production. Research shows that taking creatine supplements can increase muscle creatine by 20 to 30%. Increasing the amount of creatine found in the muscle also increases the amount of phosphocreatine, which aids in producing greater amounts of energy. This is because phosphocreatine is the limiting factor in energy production in high intensity anaerobic exercise. Thus, it is believed that supplementing the body with creatine enhances athletic performance.
What Does the Research Show?
Creatine has been shown to be effective only in certain instances, and not necessarily to the degree often advertised. Several studies suggest that creatine enhances performance in activities involving repeated short periods of intense activity. Supplementing creatine in the correct dosage with the proper duration can aid in improving athletic anaerobic performance (weight lifting, sprinting, rowing). However, creatine supplementation does not benefit endurance athletes -- marathon runners for example.
Sprinters who loaded with creatine (25 grams for 5 days) significantly increased their peak and average sprint power output compared a group taking an inactive placebo. NCAA division 1A football players who took creatine supplements for 28 days during the off season experienced gains in total body mass, and increased their weight lifting ability. They also had faster sprint times than players in a control group who did not take creatine. Male rowers who took 20 grams of creatine for 5 days significantly increased their rowing times. But not all studies find significant improvements in performance attributable to creatine. In another study of competitive rowers, those who were supplemented with .25 grams per kg of body weight had faster times, but the increase was too small to be considered statistically significant.
Marketing claims that creatine increases muscle mass are controversial. Research has shown that people who supplement with creatine do gain weight. However, more research is needed to assess how much of the weight gain is actually due to increased muscle mass.
Currently there is no evidence that creatine increases fat metabolism.
Some studies have shown that people suffering from neuromuscular disease or from congestive heart failure may improve muscle strength by taking creatine. However, more research is needs to be done in this area to confirm these findings. Preliminary research investigating the potential benefits of creatine for the elderly, found no difference in strength or body composition in people who were supplementing with creatine. It is recommended that any elderly person who elects to take creatine have their renal (kidney) function periodically.
How Much Creatine is Safe?
Since creatine is a supplement and produced naturally in the body, the Food and Drug Administration (FDA) does not currently have dosing standards. Taking a dose of 20 grams a day for one week, followed by 2-5 grams as a daily maintenance dose has not been shown to have adverse effects. However, people who exceed this dosage may be at a higher risk of developing renal disease.
People who currently suffer from renal disease should not take creatine. The consumption of creatine right before or during exercise is not recommended. It may be beneficial to increase fluid consumption when taking creatine to prevent dehydration. Caffeine may negate the benefits of creatine by inhibiting phosphocreatine resynthesis, which takes place in the recovery phase of exercise.
Creatine can also be obtained from eating a mixed diet. Animal products such as herring, pork, salmon, beef, cod and milk contain creatine naturally. Normally people ingest about 1 gram a day of creatine from their diet.
Sources:
Rosenbloom, C. 1999 Sports Nutrition: A Guide for the Professional Working with Active People. American Dietetic Association.
Sarubin, A. 1999 The Health Professional's Guide to Popular Dietary Supplements. American Dietetic Association.
Terjung, RL et al. March, 2000 American College of Sports Medicine Roundtable: the Physiological and Health Effects of Oral Creatine Supplements. Medicine and Science in Sports and Exercise 32(3):706-717.
Dena Mehlberg Outpatient Dietitian, Froedtert Hospital
Article Created: 2000-09-26Article Reviewed: 2000-09-26
Each year, Medical College of Wisconsin physicians care for more than 180,000 patients, representing nearly 500,000 patient visits. Medical College physicians practice at Children's Hospital of Wisconsin, Froedtert Memorial Lutheran Hospital, the Milwaukee VA Medical Center, and many other hospitals and clinics in Milwaukee and southeastern Wisconsin.
