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

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


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

In This Article

Physiological and Psychological Function

Table 4 presents a summary of the effects that caffeine imposes on the human body. Clearly, caffeine has multiple effects, but this does not mean that caffeine, when used in moderation, induces dehydration, electrolyte depletion, or hyperthermia. We conclude, based on the information above, that the popular beliefs about caffeine in regard to fluid balance, electrolyte balance, and exercise-heat tolerance are incorrect. Simply stated, the physiological process that oppose dehydration (i.e., arginine vasopressin effects on water retention and aldosterone effects on sodium balance) are sufficient to handle the effects of a mild diuretic that is consumed in moderation. Because dehydration is absent, the body's ability to regulate temperature (i.e., via sweating and increased skin blood flow) is not impaired, even in a hot environment. In turn, because hyperthermia is not greater when caffeine is consumed (vs a water placebo), exercise performance is enhanced without increased physiological strain.