This September Mark Tarnopolsky's group in Toronto published a study comparing the turnover rates of proteins in males and females in response to creatine supplementation. Motivated by the finding that fat-free mass increases following creatine use, these authors sought to determine if this effect is solely due to increased muscle hydration or whether increases in muscle protein content also contribute. They were also interested in determining whether creatine supplementation benefits males and females to the same extent.

Design

The sample consisted of 13 male and 14 female subjects. On average they were 23 years of age. They were asked to abstain from taking any other supplements during the study period. The design was similar to the previous study. Half of the subjects (males and females) were given placebo; the other half were loaded with 20 grams of creatine monohydrate powder a day for 5 days, followed by a maintenance dose of 5 grams of creatine for a period of 3-4 days. This was a short-term study.

Results

This study found that while the rate of new protein production did not change in response to creatine use, the rate of protein degradation decreased. It thus appeared that creatine suppressed protein degradation. In scientific jargon this would be known as an "anti-catabolic" (anti-breakdown) effect and would eventually lead to greater protein levels in supplementing individuals. This effect would also contribute to the increase in fat-free mass commonly observed with creatine use. Unfortunately, while this protein-sparing effect was apparent in males, it was virtually absent in females. The reason for this gender disparity is currently unresolved.

Interestingly, muscle creatine (and phosphocreatine) levels increased to the same extent in both males and females, explaining why fat-free mass also increases in both sexes. Remember that water follows creatine into skeletal muscle resulting in muscle volumizing and consequently in an increase in fat-free mass. In other words, the relative proportion of fat to total muscle mass, including water, decreases with creatine use. This increase in fat-free mass, however, is typically less pronounced in women, which also makes sense since the protein sparing effect of creatine is virtually absent in women.

Conclusion

This study concluded that creatine supplementation spares proteins from being degraded. Furthermore, the authors hypothesized that this was an effect downstream of muscle volumizing and is supported by experiments showing that infusing males (through their veins) with dilute saline (to induce cell swelling) exhibited similar protein sparing effects. In other words, cell swelling induced without creatine also spares proteins from being degraded. Therefore, this effect has little to do with creatine per se.