I’m not really sure why but I dug this up:
The diuretic effect of coffee was also evaluated in previous studies which Dr. Armstrong reviewed. The mild diuretic effect in coffee, tea and soda stems from their active agents, classified as methylxanthines. Dr. Armstrong explained, “The caffeine in coffee, tea, and soft drinks is 1,3,7-trimethylxanthine. Tea contains theophylline – 1,3-dimethylxanthine. Theobromine is found in tea, chocolate and cocoa as 3,7-dimethylxanthine. All three compounds are central nervous system and cardiac stimulants, as well as mild diuretics in some situations.
Both serious athletes and weekend athletes consume a number of beverages that, when taken in large volume, have a diuretic effect. It is interesting to note that researchers have shown that fluid-electrolyte replacement beverages have diuretic activity, and that even water is a diuretic. At less than 300 mg a day, the diuretic activity of caffeine is similar to that of water.
Dr. Armstrong noted that, “…virtually no evidence exists in the scientific literature that caffeine exaggerates dehydration and electrolyte loss to the point that it impairs exercise performance.” He told the science writers that neither athletes nor recreational enthusiasts will incur detrimental fluid-electrolyte imbalances if they drink caffeinated beverages in moderation and eat a well-balanced diet.
In addition to performing the review of other investigators’ work mentioned above, Dr. Armstrong discussed his own recently completed research, presented in the paper, *Fluid-electrolyte and renal indices of hydration during eleven days of controlled caffeine consumption (in review). *
He told the science writers, “Our recent investigation determined if three levels of controlled caffeine consumption affected fluid-electrolyte balance and renal function differently. Fifty-nine active males (mean + SD; age, 21.6 + 3.3 y) consumed 3 mg caffeine· kg-1·d-1 on days 1-6 (equilibration phase). On days 7-11 (treatment phase), subjects consumed either 0 mg (C0; placebo; n=20), 3 mg (C3; n=20), or 6 mg (C6; n=19) caffeine/kg body weight/day in capsules; no other dietary caffeine intake was allowed. The subjects maintained detailed records of food and fluid intake.”
Dr. Armstrong noted, “There were no significant differences between groups C0, C3 and C6 (P>0.05) for any of the hydration-relevant variables, including urine volume.”
He concluded, “We found no evidence of acute or chronic dehydration in C3 or C6 during 11 days of controlled caffeine consumption. Our findings question the widely accepted notion that caffeine acts chronically as a diuretic.“
You must have been dogging it previously