Creatine
Creatine is available in the on-line shop in several EAS supplements:
Safety of creatine
Creatine (Cr) has been in wide-spread since the early 90s and testimonies by professional athletes from a large range of sporting backgrounds has made it one of the most popular supplements in the world. Cr is primarily stored in the body in skeletal muscle and 60% this Cr is stored as phosphocreatine (PCr).
PCr plays a crucial role in energy production and the theory behind supplementation is similar to that of carbohydrate loading - the higher the availability of Cr, the longer energy supplies will last and the longer it will take for fatigue to set in. The theory that Cr supplementation will increase muscle stores of PCr is well-supported (e.g. Hultman et al. (1996) Muscle Creatine Loading in Men. Journal of Applied Physiology, 1996; 81:231-237.).
There have been many anecdotal reports of side-effects caused by Cr supplementation including muscle cramps, strains, stomach problems, kidney problems and heat illness due to water imbalances. The truth of the matter is that many of these have been one-off cases or have been attributable to other circumstances such as voluntary dehydration.
The only current side-effect which is directly linked to Cr supplementation is weight gain and this has been well-documented in scientific literature. The fact that Cr has been in such wide-spread use over the last 15 years means that if any relationship existed between it's use and serious side-effects this would have unearthed by now.
Several studies have looked at potential side-effects with the general conclusion being that Cr is not associated with any negative side-effects when taken in recommended doses (e.g. Poortmans et al. (2000) Adverse Effects of Creatine Supplementation: Fact of Fiction? Sports Medicine, 2000; 30:155-170.)
Effects on strength in untrained subjects
A 2003 study examined the effects of creatine (Cr) supplementation on muscle strength and body composition in untrained males (Kilduff et al. (2003) Effects of Creatine on Body Composition and Strength Gains After 4 Weeks of Resistance Training in Previously Nonresistance Trained Humans. IJSNEM, 13(4), Dec, 2003).
The subjects undertook 4 weeks of resistance training (3days/week) and were divided into two groups. Group 1 received a traditional Cr loading dose (20g + 140g glucose / day) for 7 days and then a maintenance dose (5g + 35g glucose / day) for 21 days. Group 2 received a placebo - 160g glucose for 7 days and 40g glucose for the remaining 21 days.
As expected, the Cr group could be sub-divided into 'responders' and 'non-responders' and this was done on the basis of body mass gains and Cr retention. The responders were found to have a greater magnitude of change in isokinetic and isometric knee extension or 'strength' as compared to the placebo group. Positive correlations were shown between body mass gains & increased 'strength' as well as Cr retention & increased 'strength' indicating that those subjects experiencing a higher uptake of Cr has a greater increase in performance.
Effects of long-term supplementation on liver and kidney function
Following anecdotal evidence suggesting that creatine (Cr) supplementation can have detrimental effects on liver and kidney function, this long-term study investigated these claims (Mayhew et al. (2002) Effects of Long-Term Creatine Supplementation on Liver and Kidney Function in American College Football Players. ISJNEM, 12(4), Dec, 2002.) 23 subjects with at least 2 years resistance training experience were divided into a Cr group in which they voluntarily took Cr supplements and a control group in which they took no supplements. The Cr group averaged regular daily intake of 5-20g Cr for 0.25-5.6 years.
Blood analyses for markers of kidney and liver function revealed no significant differences between the two groups and, within the Cr group, no correlations were found between these markers and dose or duration of supplementation. This study concluded that Cr supplementation caused no long-term detrimental effects on kidney or liver function in highly trained college athletes in the absence of other nutritional supplements.