Calcium requirements during total parenteral nutrition in well-nourished individuals.

Eleven patients, receiving all nutrition intravenously, were given varying doses of calcium (0-20 mg/kg/day) to determine an optimal level for calcium administration during postoperative parenteral nutrition. During each study period, nitrogen, phosphorus, vitamin, and caloric intakes were constant. Negative calcium balance resulted when less than 2 mg Ca++/kg body weight was given daily. During excessive urinary calcium losses, serum calcium concentration remained in the normal range. Increasing calcium intake to approximately 5 mg/kg/day (500 mg/day) yielded an apparent retention of calcium, as did higher doses. Serum calcium did not rise at this time. Urinary calcium excretion was directly proportional to calcium intake. The preliminary data suggest that a minimum dose of 5 mgCa++/kg/day is necessary to attain equilibrium between intake and urinary output. This value is higher than recent suggestions for calcium replacement during intravenous feeding.