Creatine supplements
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Creatine_supplements".

Creatine supplements are athletic aids used to increase high-intensity athletic performance. Though researchers have known of the use of creatine as an energy source by skeletal muscles since the beginning of the 20th century, they were popularized as a performance-enhancing supplement in 1992.

History of creatine supplements

In 1912, Harvard University researchers Otto Folin and Willey Glover Denis found proof that ingesting creatine can dramatically boost the creatine content of the muscle¹. In the late 1920s, after finding that the intramuscular stores of creatine can be increased by ingesting creatine in larger than normal amounts, scientists discovered creatine phosphate, and determined that creatine is a key player in the metabolism of skeletal muscle. The substance creatine is naturally formed in vertebrates.

While creatine's influence on physical performance has been well documented since the early twentieth century, it only recently came into public view following the 1992 Olympics in Barcelona. An August 7, 1992 article in The Times reported that Linford Christie, the gold medal winner at 100 meters, had utilized creatine prior to the Olympics, and an article in Bodybuilding Monthly named Sally Gunnell, gold medalist in the 400-meter hurdles, as another creatine user. Several medal-winning British rowers also used creatine during their preparations for the Barcelona games.

At the time, low-potency creatine supplements were available in Britain, but creatine supplements designed for strength enhancement were not commercially available until 1993 when a company called Experimental and Applied Sciences (EAS) introduced the compound to the sports nutrition market under the name Phosphagen.² Research conducted afterward showed that the consumption of high glycemic carbohydrates in conjunction with creatine increases creatine muscle stores and performance. ³ In 1998, MuscleTech Research and Development launched Cell-Tech, the first creatine-carbohydrate-alpha lipoic acid supplement. Alpha lipoic acid has been demonstrated to enhance muscle phosphocreatine levels and total muscle creatine concentrations. This approach to creatine supplementation was validated in a study performed in 2003.⁴

Another important event in creatine supplementation occurred in 2004 when the first creatine ethyl ester supplements were launched. Creatine ethyl ester (CEE) is becoming a widely used form of creatine, with many companies now carrying both creatine monohydrate-based supplements and CEE supplements, or combinations of both.

Creatine and athletic performance

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Creatine is often taken by athletes as a supplement for those wishing to gain muscle mass (bodybuilding). There are a number of forms but the most common are creatine monohydrate - creatine complexed with a molecule of water, and Creatine ethyl ester (CEE). A number of methods for ingestion exist - as a powder mixed into a drink, or as a capsule or caplet. Once ingested, creatine is highly bioavailable, whether it is ingested as the crystalline monohydrate form, the free form in solution, or even in meat. Creatine salts will become the free form when dissolved in aqueous solution. Conventional wisdom recommends the consumption of creatine with high glycemic index carbohydrates, though research indicates that the use of high GI carbs in combination with protein is also beneficial.⁵

There is scientific evidence that taking creatine supplements can marginally increase athletic performance in high-intensity anaerobic repetitive cycling sprints, but studies in swimmers and runners have been less than promising, most likely because these activities are sustained at a given intensity and thus do not allow for significant intra-exercise synthesis of additional creatine phosphate molecules. Ingesting creatine can increase the level of phosphocreatine in the muscles up to 20%. It must be noted creatine has no significant effect on aerobic endurance, though it will increase power during aerobic exercise.⁶

Since body mass gains of about 1 kg can occur in a week's time, many studies suggest that the gain is simply due to greater water retention inside the muscle cells. However, studies into the long-term effect of creatine supplementation suggest that body mass gains cannot be explained by increases in intracellular water alone.⁷ In the longer term, the increase in total body water is reported to be proportional to the weight gains, which means that the percentage of total body water is not significantly changed. The magnitude of the weight gains during training over a period of several weeks argue against the water-retention theory.

Also, research has shown that creatine increases the activity of satellite cells, which make muscle hypertrophy possible. Creatine supplementation appears to increase the number of myonuclei that satellite cells will 'donate' to damaged muscle fibers, which increases the potential for growth of those fibers. This increase in myonuclei probably stems from creatine's ability to increase levels of the myogenic transcription factor MRF4.⁸⁹.

In another study, researchers concluded that changes in substrate oxidation may influence the inhibition of fat mass loss associated with creatine after weight training when they discovered that fat mass did not change significantly with creatine but decreased after the placebo trial in a 12-week study on ten active men. The study also showed that 1-RM bench press and total body mass increased after creatine, but not after placebo.¹⁰ The underlying effect of Creatine on body composition if there is indeed one has yet to be determined, as another study with a similar timeframe suggests no effect on body composition, but had less overall emphasis on metabolic effects. ¹¹

Creatine use is not considered doping and is not banned by the majority of sport-governing bodies. However, in the United States, the NCAA recently ruled that colleges could not provide creatine supplements to their players, though the players are still allowed to obtain and use creatine independently.

Creatine ethyl ester

Main article: Creatine ethyl ester

CEE is a form of commercially available creatine touted to have higher absorption rates and a longer serum half-life than regular creatine monohydrate by several supplement companies. No peer-reviewed studies have emerged on creatine ethyl ester to conclusively prove these claims, however, a study presented at the 4th International Society of Sports Nutrition (ISSN) annual meeting demonstrated that the addition of the ethyl group to creatine actually reduces acid stability and accelerates its breakdown to creatinine. The researchers concluded that creatine ethyl-ester is inferior to creatine monohydrate as a source of creatine.¹²

As a supplement, the compound was developed, patented and licensed through UNeMed, the technology transfer entity of the University of Nebraska Medical Center.¹³

Safety

Current studies indicate that short-term creatine supplementation in healthy individuals is safe.¹⁴¹⁵¹⁶ Small-scale, longer-term studies have been done and seem to demonstrate its safety.¹⁷¹⁸¹⁹ There have been reports of muscle cramping with the use of creatine, though a study showed no reports of muscle cramping in subjects taking creatine-containing supplements during various exercise training conditions in trained and untrained endurance athletes.²⁰²¹ The cause of the reported cramping by some users may be due to dehydration, and extra water intake is vital when supplementing with creatine.

In addition, experiments have shown that creatine supplementation improved the health and lifespan of mice.²² Whether these beneficial effects would also apply to humans is still uncertain.

Creatine supplementation, in the dosages commonly used, results in urinary concentrations that are 90 times greater than normal. The long term effects of this have not been investigated, but there is possibility for a variety of nephrotoxic, i.e., kidney damaging, events. There is potential for direct toxicity on renal tubules where urine is formed, and for acceleration of kidney stone formation.²³

Although studies indicate that Creatine is safe for healthy athletes, Creatine has been shown to accelerate the growth of cysts in rats with Polycystic Kidney Disease (PKD). ²⁴ Studies have not yet determined if Creatine supplementation will accelerate the growth of cysts in humans with PKD. PKD is prevelant in approximately 1 in 1000 people and may not be detectable until affected individuals reach their thirties.

Creatine and mental performance

Creatine administration was shown to significantly improve performance in cognitive and memory tests in vegetarian individuals involved in double-blind, placebo-controlled cross-over trials.²⁵ Vegetarian supplementation with creatine seems to be especially beneficial as they appear to have lower average body stores, since meat is a primary source of dietary creatine. ²⁵

References