Clinical experience of zinc supplementation during intravenous nutrition in Crohn's disease: value of serum and urine zinc measurements.

Serum zinc concentrations and urine zinc excretion have been studied in 10 patients with severe Crohn's disease before and during 59 patient-weeks of intravenous nutrition. Before serum zinc concentrations (9.9 +/- 1.0 mumol/l: mean +/- SEM) and urine zinc excretion (3-3 +/- 0.6 mumol/24h) were less than controls (p less than 0.01). No patients had clinical signs of zinc deficiency before intravenous nutrition and none developed signs during it. There was no overall change in serum zinc concentrations, despite improvements in body weight, skinfold thickness, and mid-arm circumference in all patients, and increased serum albumin and serum transferrin concentrations during all but two periods of intravenous nutrition. Nor was there any relationship between serum zinc concentrations and zinc uptake (up to 220 mumol/day), serum zinc concentrations remaining significantly lower than control levels. Urine zinc excretion during the first week of intravenous nutrition showed a 1.2 to 53-fold increase (mean 11-fold) over pre-intravenous nutrition levels, and a positive relationship was demonstrated between zinc intake and urine zinc excretion. It is suggested that zinc supplied by the intravenous route is inefficiently transported to the tissues, and that some is excreted in the form of small molecular weight chelates into urine. Recommendations are made for the supply of intravenous zinc, based on monitoring urine zinc excretion in individual patients.