Nutrient interactions with total parenteral nutrition: effect of histidine and cysteine intake on urinary zinc excretion.

Because cysteine and histidine, two amino acids included in total parenteral nutrition regimens, bind zinc and increase its renal ultrafilterability, my objective was to quantify the effects of infusion of amino acids, including cysteine and histidine, on urinary zinc excretion. The effect of the infusion of high amounts of cysteine and no cysteine (100 mg/kg/day vs none) and of high and low amounts of histidine (165 vs. 95 mg/kg/day) on urinary zinc excretion was determined in 14 newborn infants receiving total parenteral nutrition who had similar zinc intakes (approximately 7 mumol/kg/day). After a 72-hour adaptation period, each infant's urine was collected for two 48-hour periods. Urinary zinc excretion during the high-dose histidine and cysteine infusion periods was significantly elevated compared with that during the no-cysteine and low-dose histidine periods. Therefore concurrent intakes of specific amino acids may have to be considered when zinc dosages are calculated.