Use of oral contraceptives blunts the calciuric effect of caffeine in young adult women.

Caffeine consumption increases the urinary excretion of calcium and other minerals. Factors that affect caffeine metabolism such as steroid hormones may modify this effect. The purpose of this study was to evaluate the influence of oral contraceptive (OC) use on the 4-h urinary excretion of calcium, phosphorus, magnesium, zinc, sodium, potassium and caffeine metabolites in response to a high caffeine dose given as coffee beverage.