January 7, 2008

Facts and Benefits of Creatine - Part 2 of 5

Facts and Benefits of Creatine: Creatine has become one of the most extensively studied and scientifically validated nutritional ergogenic aids for athletes. Additionally, creatine has been evaluated as a potential therapeutic agent in a variety of medical conditions such as Alzheimer's and Parkinson's diseases.

In terms of potential medical applications, creatine is intimately involved in a number of metabolic pathways. For this reason, medical researchers have been investigating the potential therapeutic role of creatine supplementation in a variety of patient populations.

Creatine is chemically known as a non-protein nitrogen; a compound which contains nitrogen but is not a protein per se. It is synthesized in the liver and pancreas from the amino acids arginine, glycine, and methionine. Approximately 95% of the body's creatine is stored in skeletal muscle. Additionally, small amounts of creatine are also found in the brain and testes.

About two thirds of the creatine found in skeletal muscle is stored as phosphocreatine (PCr) while the remaining amount of creatine is stored as free creatine. The total creatine pool (PCr + free creatine) in skeletal muscle averages about 120 grams for a 70 kg individual. However, the average human has the capacity to store up to 160 grams of creatine under certain conditions.

The body breaks down about 1-2% of the creatine pool per day (about 1-2 grams/day) into creatinine in the skeletal muscle. The creatinine is then excreted in urine. Creatine stores can be replenished by obtaining creatine in the diet or through endogenous synthesis of creatine from glycine, arginine, and methionine.

Dietary sources of creatine include meats and fish. Large amounts of fish and meat must be consumed in order to obtain gram quantities of creatine. Whereas dietary supplementation of creatine provides an inexpensive and efficient means of increasing dietary availability of creatine without excessive fat and/or protein intake.

Various supplementation protocols have been suggested to be efficacious in increasing muscle stores of creatine. The amount of increase in muscle storage depends on the levels of creatine in the muscle prior to supplementation.

Those who have lower muscle creatine stores, such as those who eat little meat or fish, are more likely to experience muscle storage increases of 20–40%, whereas those with relatively high muscle stores may only increase stores by 10–20%. The magnitude of the increase in skeletal muscle creatine content is important because studies have reported performance changes to be correlated to this increase.

The supplementation protocol most often described in the literature is referred to as the "loading" protocol. This protocol is characterized by ingesting approximately 0.3 grams/kg/day of creatine monohydrate for 5-7 days (e.g., 5 grams taken four times per day) and 3-5 grams/day thereafter.

Research has shown a 10-40% increase in muscle creatine and phosphocreatine stores using this protocol. Additional research has reported that the loading protocol may only need to be 2–3 days in length to be beneficial, particularly if the ingestion coincides with protein and/or carbohydrate. Furthermore, supplementing with 0.25 grams/kg-fat free mass/day of creatine monohydrate may be an alternative dosage sufficient to increase muscle creatine stores.

Other suggested supplementation protocols utilized include those with no loading phase as well as "cycling" strategies. A few studies have reported protocols with no loading period to be sufficient for increasing muscle creatine (3 g/d for 28 days) as well as muscle size and strength (6 g/d for 12 weeks).

These protocols seems to be equally effective in increasing muscular stores of creatine, but the increase is more gradual and thus the ergogenic effect does not occur as quickly. Cycling protocols involve the consumption of "loading" doses for 3–5 days every 3 to 4 weeks. These cycling protocols appear to be effective in increasing and maintaining muscle creatine content before a drop to baseline values, which occurs at about 4–6 weeks.

Reproduced with minor omissions, including references for ease of reading, from: Buford TW, Kreider RB, Stout JR, Greenwood M, Campbell B, Spano M, Ziegenfuss T, Lopez H, Landis J, Antonio J. International Society of Sports Nutrition position stand: creatine supplementation and exercise. Journal of the International Society of Sports Nutrition 2007, 4:6 (30 August 2007). doi:10.1186/1550-2783-4-6. © 2007 Buford et al; licensee BioMed Central Ltd.This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0).

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