Caffeine, Fluid-Electrolyte Balance, Temperature Regulation, and Exercise-Heat Tolerance

Lawrence E. Armstrong; Douglas J. Casa; Carl M. Maresh; Matthew S. Ganio

Disclosures

Exerc Sport Sci Rev. 2007;35(3):135-140. 

In This Article

Summary And Future Research

A variety of investigations have been reviewed spanning more than 75 yr. The evidence indicates that consuming a moderate level of caffeine results in a mild increase of urine production. Although this diuresis may (240-642 mg of caffeine) or may not (<240 mg) be significantly greater than a control fluid (0 mg of caffeine), there is no evidence to suggest that moderate caffeine intake (<456 mg) induces chronic dehydration or negatively affects exercise performance, temperature regulation, and circulatory strain in a hot environment. Caffeinated fluids contribute to the daily human water requirement in a manner that is similar to pure water. It is possible that urinary Na+, but less likely that urinary K+, excretion is increased somewhat by caffeine consumption; however, an affluent Western diet provides Na+ and K+ in amounts that exceed these losses. Furthermore, little or no evidence supports the contention that caffeine increases heat storage during exercise or that caffeine affects exercise performance in a hot environment negatively. Finally, little is known about the efficacy of caffeine administration regarding the following: a) large doses of caffeine (>600 mg) that are consumed at one time and b) differences between modes of caffeine delivery (i.e., via capsules, tablets, coffee, tea, soft drinks, sport drinks, and solid food). These are worthy of future research.

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