Coffee, caffeine & hydration in the general population – Part 1Print this page 11 Oct 2013
Caffeinated beverages and urinary excretion
In a study, which investigated the effect of coffee drinking on urine excretion, it was revealed that those who drank coffee saw a significant increase in the volume of urine excreted, compared to those who drank the same volume of water. When participants were given six cups of coffee (642mg of caffeine), a 41% increase in 24-hour urine excretion was observed.
Further findings conclude that the acute ingestion of caffeine in large doses (at least 250-300mg, equivalent to the amount found in 2-3 cups of coffee or 5-8 cups of tea) results in a short-term stimulation of urine output in individuals who have been deprived of caffeine for a period of days or weeks. Tolerance to the mild, short-term diuretic effects of caffeine develops, however, and these effects are diminished in individuals who regularly consume tea or coffee.
More recently, a study of 59 subjects looked at the influence of caffeine on possible fluid imbalance under three conditions. The participants consumed 3mg caffeine per kg/body weight on days 1 to 6. On days 7 to 11, the treatment phase, subjects consumed either 0mg, 3mg or 6mg caffeine per kg/body weight. The healthy, active males taking part in the study across the condition showed no evidence of dehydration.
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