INTERACTIONS BETWEEN DIETARY CALCIUM AND CAFFEINE CONSUMPTION ON CALCIUM-METABOLISM IN HYPERTENSIVE HUMANS

Abnormal calcium metabolism has been implicated in human hypertension. Caffeine consumption may contribute to hypertension since it increase s urinary calcium excretion. Nineteen hypertensive subjects (HTN) and nineteen age and gender matched normotensive controls (NTC) who habitu ally consumed at least 175 mg caffeine daily were studied before and a fter abstinence from all caffeine (CAF) consumption for 2 weeks: Caffe ine abstinence (CAF-) increased fasting serum ultrafiltrable calcium i n HTN and NTC, but not serum total calcium. Parathyroid hormone (PTH) levels decreased after CAF abstinence in 14 of 18 HTN subjects, includ ing all seven subjects consuming less than 700 mg calcium daily. Three day dietary calcium intakes and 72 h urinary excretion of calcium wer e not different between CAF+ and CAF- or between HTN and NTC. A mornin g caffeine dose of 6 mg/kg lean body mass increased urinary Ca/creatin ine ratios similarly for 2 h after beverage consumption in both HTN an d NTC. Caffeine consumption stresses calcium metabolism in hypertensiv e individuals, especially those consuming less than 700 mg calcium dai ly.