Zinc metabolism in adolescents with Crohn's disease.

Low serum zinc concentrations have been reported in Crohn's disease (CD) and overt zinc deficiency has been described, but little is known about the effect of CD on zinc metabolism in adolescents. The aim of this study was to measure zinc absorption, endogenous fecal zinc excretion, urinary zinc excretion, and zinc balance in children with stable CD and in matched controls. Subjects were 15 children, ages 8-18 y, with stable CD, and 15 healthy matched controls. Subjects were adapted to diets providing 12 mg/d elemental zinc for 2 wk, and then admitted for a 6-d metabolic study. Stable zinc isotopes were given intravenously and orally, and urine and feces collected for 6 d. Fractional zinc absorption, endogenous fecal zinc excretion, and zinc balance were calculated using established stable isotope methods. In subjects with CD, zinc absorption (10.9% +/- 6.1 versus 23.4 +/- 15.8, p = 0.008) and plasma zinc concentration (0.85 mg/dL +/- 0.15 versus 1.25 +/- 0.35, p = 0.004) were significantly reduced, compared with controls. Despite this, there were no significant differences in endogenous fecal zinc excretion (2.0 mg +/- 1.5 versus 1.5 +/- 1.5, p = 0.34) or urinary zinc excretion (0.9 mg +/- 0.7 versus 1.0 +/- 0.7, p = 0.47). Zinc balance was significantly lower in CD (-1.5 mg +/- 1.5) than in controls (+0.6 mg +/- 3.1, p < 0.0001). In conclusion, adolescents with CD have significantly reduced zinc absorption. Despite this, they were unable to reduce endogenous fecal zinc excretion to restore normal zinc balance and had a significantly worse zinc balance and lower plasma zinc concentration than controls.