Does caffeine in a sports drink promote dehydration? After all, the argument goes, caffeine is a diuretic so won’t that lead to dehydration, despite the ergogenic benefits? Several studies have shown that caffeine ingestion during exercise does not influence weight loss, sweat rates, urine output and plasma volume compared to water alone (2, 5). This may be due to decreased kidney blood flow during exercise which is proportional to exercise intensity (1, 3, 4) which minimizes urine production. Therefore, it appears that caffeine will not lead to diuresis if consumed during exercise – and will not contribute to dehydration.
1. Armstrong RB, Delp MD, Goljan EF, and Laughlin MH. Distribution of blood flow in muscles of miniature swine during exercise. Journal of applied physiology 62: 1285-1298, 1987.
2. Millard-Stafford ML, Cureton KJ, Wingo JE, Trilk J, Warren GL, and Buyckx M. Hydration during exercise in warm, humid conditions: effect of a caffeinated sports drink. Int J Sport Nutr Exerc Metab 17: 163-177, 2007.
3. Mueller PJ, O’Hagan KP, Skogg KA, Buckwalter JB, and Clifford PS. Renal hemodynamic responses to dynamic exercise in rabbits. Journal of applied physiology 85: 1605-1614, 1998.
4. Wahren J, Felig P, Ahlborg G, and Jorfeldt L. Glucose metabolism during leg exercise in man. Journal of Clinical Investigation 50: 2715-2725, 1971.
5. Wemple RD, Lamb DR, and McKeever KH. Caffeine vs caffeine-free sports drinks: effects on urine production at rest and during prolonged exercise. Int J Sports Med 18: 40-46, 1997.