Coffee, caffeine & hydration in the general population – Part 1

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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.

For more information on coffee and fluid balance click here, and to view information sources, click here.

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