| After an overnight fast, twenty-nine adult women ages 35 - 69 drank decaffeinated coffee to which 0, 3 or 6 mg/kg body weight caffeine had been added. Urine was collected at one, two and three hours. Urinary calcium, sodium, chloride, and magnesium excretion (mg/mg creatinine) were increased, but not creatinine, volume, phosphorus and potassium.;In a separate experiment, 18 adolescents drank, in a caffeine-free soft drink, two levels of caffeine (0 and 3 mg/kg) and two levels of sucrose (0 and 30g). Calcium, sodium, chloride and potassium excretion (mg/mg creatinine) increased after caffeine consumption, but phosphorus and magnesium were not. Total output of calcium (mg) increased from 16.6 mg (control) to 20.0 mg after caffeine to 29.6 mg after caffeine and sucrose. This increase was a trend for caffeine (p = .08) and sucrose (p = .07). Increased sodium and decreased potassium urinary excretion were associated with sucrose intake. A trend toward higher urine volume was observed after caffeine ingestion, but not after sucrose intake. A trend toward increased calcium concentration was observed with sucrose intake, but after caffeine intake, calcium concentration was not increased. A sex/caffeine interaction was apparent. In male subjects calcium concentration decreased after caffeine intake whereas in female adolescents, calcium concentrations were increased. Caffeine and sucrose did not interact in this study, indicating that they do not increase calcium excretion by competing mechanisms. Caffeine consumption was negatively correlated with calcium intake.;Twenty of these women also took 1300 mg of aspirin to inhibit prostaglandin release before consuming 0 and 3 mg/kg caffeine a second time. Caffeine consumption again increased calcium, sodium, chloride, and magnesium excretion (mg/mg creatinine) in spite of aspirin ingestion, thus the effects of caffeine probably are not mediated by prostaglandin. Aspirin alone did not affect the total excretion of any of the minerals studied, but did increase urine volume, thereby decreasing urinary mineral concentrations. |
