Does caffeine affect creatine?

Some studies suggest reduced effectiveness of creatine when consumed with caffeine (Vandenburghe, et al 1996; Hespel, et al 2002), but these have flaws. In Vandenburghe's study, subjects when using creatine together with caffeine (C+C) had lower levels of performance than when they were administered creatine alone (C) (when also compared to placebo). However as CP levels were similar in C+C and C, this indicates that caffeine did not impair the transportation of creatine into muscle.

The studies were not under strict guidelines, which may explain the reduced performance: There was not a significant clearance period of creatine from stores before subjects were given the next test. Also, there was only 3 weeks rest, which may show signs of creatine storage; 4 weeks is more likely to give full clearance. So, if C+C was tested first, there may have still been some creatine in the stores. For optimal study design, a 6-week gap seems appropriate.

Another large flaw was that there was only 20 hours between the last caffeine dose and the C+C test results. This is more than enough time for caffeine to be out the system, i.e. caffeine could have had no effect (we have already showed it didn't affect muscle uptake).

Earlier studies by Greenhaff, et al (1993) where hot tea/coffee were used to promote dissolvation and absorption of creatine, showed enhanced performance, which contradicts these findings.

Hespel, et al (2002) were different in their study design but there were still a number of flaws mainly due to the timings of caffeine intake, similar to that of Vandenburghe et al in this respect.

It is crucial to bear in mind that the ultimate limiting factor for exercise performance is hydration state (I cannot emphasise enough the importance of this), and one of the positive effects of creatine is cell volumisation, i.e. more fluid into muscles. If there is insufficient fluid in the body, then valuable extracellular water will be drawn into muscles. Caffeine in higher quantities is a diuretic, and may reduce hydration state; this could explain reduced performance and is easily rectified by drinking plenty of fluid whilst on a creatine cycle.

There is nothing wrong with taking creatine in a caffeinated beverage, nor with using caffeine pills pre-workout whilst on a creatine cycle, as long as you drink plenty of fluid throughout the day.