Over the last decade, hundreds of articles have been written about creatine in scientific journals, magazines, newspapers, and on the Internet. The reason for this interest is that creatine has proven to be one of the most effective nutritional supplements available for strength/power athletes and some patient populations. Moreover, a number of concerns have been raised about the safety of creatine supplementation and ethics of athletes taking performance enhancing nutritional supplements. While a number of very good reviews have been published about creatine in the scientific literature, a significant amount of misinformation has also been written about creatine particularly in the popular media. The result is that people are often confused about the potential benefits and risks of creatine supplementation. The purpose of this overview is to provide and update as to the state of the science regarding creatine supplementation. Additionally, to answer some common questions about creatine so that you can make an informed decision about whether to use creatine to enhance various strength and conditioning training protocols.
What is creatine?Creatine is a naturally occurring amino acid that is found primarily in the muscle (95%). There is also a small amount of creatine in the brain and testes. Most of the creatine found in the muscle is stored as phosphocreatine (66%) while the remaining amount of creatine is stored as free creatine (33%). The total creatine pool (phosphocreatine + free creatine) in the muscle averages about 120 grams for a normal sized person. However, the body has the capacity to store up to 160 grams of creatine under certain conditions.
Where does my body get creatine?The body breaks down 1 to 2% (about 2 grams) of the creatine pool per day into creatinine in the muscle. The creatinine is then excreted in urine. The body replenishes lost creatine in two ways. First, about half of your daily creatine needs can be obtained from your normal diet by eating foods that contain creatine. For example, there is about 2 grams of creatine in a pound of uncooked beef and salmon. The remaining amount of creatine is synthesized from the amino acids glycine, arginine, and methionine under normal conditions. However, some people have creatine synthesis deficiencies and therefore must depend on dietary availability of creatine to maintain normal muscle concentrations.
Does creatine supplementation increase muscle creatine stores?Numerous studies indicate that dietary supplementation of creatine monohydrate increases muscle creatine and phosphocreatine content by 10 to 40%. In simple terms, one can think of the normal creatine content of the muscle (about 120 grams) as being a gas tank that is 3/4 full. Creatine supplementation typically allows an individual to fill up their creatine storage tank up to 150 to 160 grams (i.e., 20 to 30%).
What are the theoretical benefits of creatine supplementation?Increasing muscle availability of creatine and phosphocreatine can affect exercise and training adaptations in several ways. First, increasing the availability of phosphocreatine in the muscle may help maintain availability of energy during high intensity exercise like sprinting and intense weightlifting. Second, increasing the availability of phosphocreatine may help speed recovery between sprints and/or bouts of intense exercise. This may allow an athlete to do more work over a series of sprints and/or sets of exercise. Theoretically, this may lead to greater gains in strength, muscle mass, and performance over time.
Does creatine supplementation increase muscle creatine content in everyone?Some people appear to respond better than others to creatine supplementation. In this regard, individuals with lower initial creatine concentrations (e.g., vegetarians or patients with creatine synthesis deficiencies) typically have the largest increase in muscle creatine stores following creatine supplementation. Additionally, creatine supplementation may only increase muscle creatine content by 5 - 15% in some people while increasing creatine content by 15 - 40% in others. There is some evidence that the ergogenic benefits of creatine supplementation are related to the magnitude of change in muscle creatine stores. However, research has also indicated that if you follow some of the recommendations below, everyone will respond to creatine supplementation.
Does creatine supplementation effect exercise performance or training adaptations?The true test of any ergogenic aid is whether it works. As of this writing, there have been over 350 studies on creatine supplementation. Of these, about 250 have evaluated the ergogenic value of creatine supplementation. The majority of these studies (about 65%) indicate that creatine supplementation promotes a statistically significant improvement in exercise capacity. This generally means that 95 times out of 100, if you take creatine as described in the study, you will experience an improvement in exercise performance. The average gain in performance from these studies ranges between 10 to 15%. Short-term creatine supplementation appears to work best during high intensity exercise like repetitive sprinting and weightlifting. Long-term creatine supplementation appears to enhance the quality of training generally leading to 5 to 15% greater gains in strength and performance. Nearly all studies indicate that creatine supplementation increases body mass by about 1 to 2 kg in the first week of loading. In training studies, subjects taking creatine typically gain twice as much body mass and/or fat free mass (an extra 2 to 4 pounds of muscle mass during 4 to 12 weeks of training) than subjects taking a placebo. In our research, we have consistently seen some of our athlete's gain 5 to 15 pounds of muscle mass during 4 to 8 weeks of training. No study that we are aware of shows that creatine supplementation significantly decreases exercise capacity. If fact, nearly all of the studies reporting non-significant results following creatine supplementation report a 1 to 10% gain in performance. In most instances, the lack of statistical significance appears to be due to small sample sizes, high variability in conducting performance tests, and/or methodological concerns. Other than possibly carbohydrate, no other nutritional ergogenic aid has consistently reported such ergogenic benefit.
What is the best dosage?The most common way to increase muscle creatine stores is to "load" creatine by taking 0.3 grams/kg/day of creatine monohydrates (about 15 - 30 grams/day depending on body weight) divided into 3 to 4 daily doses for 5 to 7 days. Then, take 3 - 5 grams/day of creatine to maintain elevated creatine stores. More recently, studies indicate that ingesting 2 - 3 grams/day for 28-days will increase muscle concentrations of creatine as effectively as creatine loading techniques.
Should I load or not?Research has shown that the most rapid way to increase muscle creatine stores is to follow the loading method described above. Most of the creatine is taken up by muscle during the first 2 to 3 days of the loading period. While there is one study that suggests that taking lower doses of creatine over time (3 grams/day for 28 days) increased muscle creatine content, it is less clear whether this low dose protocol enhances exercise capacity. We are only aware of one well-controlled study that reported that low dose creatine supplementation (5 grams/day of creatine for 10 weeks) promoted greater gains in strength and muscle mass during training. On the other hand, several other studies found no effect of low dose (2 to 3 grams/day), long-term creatine supplementation on exercise capacity. Consequently, we recommend that people follow the creatine loading technique and then use lower doses to maintain creatine stores. You may also note that we recommend taking 5 grams/day of creatine during maintenance phases rather than 2 to 3 grams/day (0.03 grams/kg/day) that some have recommended. The reason for this is that our research has shown that many of the athletes we have monitored (particularly larger athletes) retain 2 to 4 grams of creatine per day after loading periods. Therefore, using a 5 grams/day maintenance dose appears to be necessary to maintain creatine stores in some individuals.
When is the best time to take creatine?Research indicates that intense exercise increases anabolic hormone release. Additionally, ingesting carbohydrate (e.g., 1.5 grams/kg) and protein (e.g., 0.5 grams/kg) following intense exercise may accelerate glycogen resynthesis as well as promote protein synthesis. The primary mechanism appears to be related to a carbohydrate and protein stimulated increase in insulin. Since insulin levels enhance creatine uptake and creatine has been suggested to promote protein synthesis, we generally recommend that once an athlete has loaded with creatine, that they take creatine with a carbohydrate and protein supplement following their workout.
Do men and women respond differently to creatine supplementation?About a third of the studies on creatine have evaluated women and/or mixed cohorts of men and women. Several short-term studies on female athletes have revealed limited ergogenic value. This has led some researchers to question whether women respond to creatine differently than men. However, a number of recent well-controlled short- and long-term studies in women have reported ergogenic benefits. In our research, we have found that women typically observe ergogenic benefit following short-term supplementation. However, gains in body mass and fat free mass are generally not as rapid as men. Nevertheless, women do gain strength and muscle mass over time during training.
What are the side effects of creatine?The only side effect from creatine supplementation reported in the scientific and medical literature has been weight gain. However, there have been a number of anecdotally reported side effects of gastrointestinal distress, muscle cramping, dehydration, or increased risk to musculoskeletal injury (i.e., muscle strains/pulls). Additionally, there has also been concern that short and/or long-term creatine supplementation may increase renal stress and/or adversely affect the muscles, liver, or other organs of the body. Over the last few years a number of studies have attempted to assess the medical safety of creatine. So far, well-controlled studies indicate that creatine is not associated with any of these anecdotally reported problems. In fact, there is recent evidence that creatine may lessen heat stress and reduce the susceptibility to musculoskeletal injuries. People who take creatine may experience some of these problems. However, the incidence of occurrence in creatine users does not appear to be greater than subjects who take placebos.
Should children or teenagers take creatine?No study has indicated that creatine supplementation may be harmful for children or adolescent athletes. However, it should be noted that much less is known about the effects of creatine supplementation in younger individuals. Consequently, it is our view that children and adolescent athletes should not take creatine unless it is medically prescribed or they are past puberty; they are eating a well-balance diet; they are involved in serious training that may potentially benefit from creatine supplementation; that they and they're parents are well informed about creatine; and, that the supplementation program is supervised to make sure they take quality supplements in the proper manner.
Does creatine supplementation cause athletic injuries?There have been many anecdotal reports suggesting that creatine supplementation causes muscle cramping, muscle injuries, dehydration, diarrhea, and/or a combination of these. However, to date, the only research substantiated side effect noted with creatine supplementation is weight gain. Researchers representing the Exercise & Sport Nutrition Lab at the University of Memphis have investigated the effects of creatine supplementation on the incidence of cramping/injury during college football three-a-day training and during the regular season. The results of these studies suggest that creatine supplementation during three-a-day training and during the regular season did not increase the incidence of injury or cramping. In fact, among creatine users, cramping and injury rates were lower and/or proportional to athletes who did not take creatine. In a replication study, investigators at Arkansas State University found almost identical results with college football and baseball players. Here again, creatine supplementation did not increase the incidence of injury or cramping in creatine users compared to non-creatine users. In another investigation, Gallo and associates found that seven weeks of high-dose creatine supplementation did not result in a higher incidence of sports-related injuries with national class soccer players ages 18-20. Finally, Poortman and Francaux have reviewed the current research to determine if adverse effects of creatine supplementation are fact or fiction. Many topics were discussed in the article, but in relation to side effects associated with creatine supplementation, the authors concluded that reports of muscle cramping and gastrointestinal distress are anecdotal.
Is long-term creatine supplementation safe?Elite athletes have been using creatine as a nutritional supplement since the mid 1960's. However, widespread use of creatine as a dietary supplement did not begin until the early 1990's. No negative side effects directly attributable to creatine supplementation have been reported in the scientific literature. Nevertheless, there are some concerns about the long-term side effects of creatine supplementation. Over the last year or so, a number of researchers have begun to report long-term safety data on creatine supplementation. So far, no long-term side effects have been observed in athletes (up to 5 years), infants with creatine synthesis deficiency (up to 3 years), or in patient populations (up to 5 years). One cohort of patients has been monitored for over 17-years with no significant side effects. Conversely, research has demonstrated a number of potentially helpful clinical uses of creatine in heart patients, infants and patients with creatine synthesis efficiency, patients suffering orthopedic injury, and patients with various neuromuscular diseases. There are even several studies indicating that creatine supplementation may improve blood lipid profiles which is associated with a reduction in risk to heart disease. Consequently, all available evidence suggests that creatine supplementation appears to be safe when taken within recommended guidelines.
Closing comments on creatine!The future of creatine research is very promising. Researchers are attempting to determine ways to maximize creatine storage in the muscle, which types of exercise may obtain the greatest benefit from creatine supplementation, the potential medical uses of creatine, and the long-term safety and efficacy of creatine supplementation. Among these, the most promising area of research is determining the potential medical uses of creatine particularly in patients with creatine synthesis deficiencies and neuromuscular diseases. Nevertheless, in regards to athletes, creatine has continually proved itself to be one of the most effective and safe nutritional supplements to increase strength, muscle mass, and performance. This is despite all of the inaccurate and misleading information that has been written about creatine over the last several years.
Mike Greenwood PhD, CSCS*D
Human Performance Laboratory
Department of HPESS
Arkansas State University
State University, Arkansas, USA
Richard B. Kreider PhD, FACSM
Exercise & Sport Nutrition Laboratory
Human Movement Sciences & Education
University of Memphis
Memphis, Tennessee, USA
Dr. Greenwood serves as Associate Professor and Graduate Coordinator in the Department of Health, Physical Education, and Sport Sciences at Arkansas State University. Dr. Greenwood also serves as a research associate in the Exercise & Sport Nutrition Laboratory in the Department of Human Movement Sciences & Education at The University of Memphis. Dr. Greenwood has made over 100 national/international presentations to scholarly forums and published more than 60 research articles/abstracts in scientific journals in the areas of sport nutrition and strength and conditioning. Dr. Greenwood serves as a member of the editorial board for the National Strength and Conditioning Association's (NSCA) Strength and Conditioning Journal. Dr. Greenwood is an active member of the American College of Sport Medicine (ACSM) and is certified with distinction as a strength and conditioning specialist with the National Strength and Conditioning Association (NSCA). In addition, Dr. Greenwood has served as an NCAA baseball and basketball coach as well as a college strength and conditioning specialist.
Dr. Kreider serves as Professor, Assistant Chair, and Director of the Exercise & Sport Nutrition Laboratory in the Department of Human Movement Sciences & Education at The University of Memphis. Dr. Kreider has conducted numerous studies on nutrition and exercise including studies on carbohydrate, amino acids/protein, sodium phosphate, creatine, calcium HMB, conjugated linoleic acids (CLA), pyruvate, and various nutritional formulations. Dr. Kreider has published more than 150 research articles/abstracts in scientific journals, is lead editor of Overtraining in Sport (Human Kinetics, 1998), and is coauthor of Creatine: The Power Supplement (Human Kinetics, 1999). Dr. Kreider serves as Research Digest editor for the International Journal of Sport Nutrition and member of the editorial board of the Journal of Strength and Conditioning Research. Dr. Kreider is a Fellow of the American College of Sport Medicine (ACSM), is ACSM certified as an Exercise Specialist and Health/Fitness Director, and is an active member of the National Strength and Conditioning Association (NSCA). Dr. Kreider is a contributing author to numerous fitness magazines and serves as a scientific consultant for the media and nutrition industry.