|MadSci Network: Biochemistry|
A search of the medical literature revealed 2 articles on caffeine and calculating "water balance." In one of those, subjects did not consume any caffeine or related substances for 5 days and then were given 6 cups of coffee containing 642 mg of caffeine. They had an average negative water balance of 753 +/- 532 ml over the next 24 hours. (Neuhauser-Berthold, Beine S, Verwied SC, Luhrmann PM. Coffee consumption and total body water homeostasis as measured by fluid balance and bioelectrical impedance analysis. Ann Nutr Metab 1997;41(1):29-36). In the other article, the authors used figures of 1.17 ml water lost/mg caffeine consumed and 10 ml water lost/ g alcohol in calculating water balance (Stookey JD. The diuretic effects of alcohol and caffeine and total water intake misclassification. Eur J Epidemiol 1999 Feb;15(2):181-8). I am not sure of the derivation of these numbers, although the number for caffeine is the same as that of the Neuhauser-Berthold et al. article. I could not find any reference to the caffeine content of different beverages having different effects; it appears to be a function of the amount of caffeine present and not the source of the caffeine. Similarly, with alcohol, the effect seems to be a function of the amount of alcohol consumed and not the source of the alcohol. C
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