Zinc utilization in pregnant and nonpregnant women fed controlled diets providing the zinc RDA.

Eight pregnant (P) women in their third trimester and 10 nonpregnant (NP) women participated in a 21-day confined metabolic study. The participants were fed semipurified liquid diets providing 20 mg zinc/day. Apparent zinc balance was calculated and parameters of zinc status assessed. Even though an adequate amount of a readily available form of zinc was fed, the P women consistently maintained lower mean serum zinc concentrations than the NP controls (69 micrograms/dl vs. 97 micrograms/dl). Although the dietary zinc intake was constant throughout the study, most subjects' salivary zinc levels varied greatly. In this study, salivary zinc concentrations was not a sensitive indicator of zinc intake. There were no differences in the concentrations of zinc in hair between the P and NP groups; mean values ranged from 180--220 ppm. In both groups, approximately 95% of the measured zinc output was lost in the feces and only 5% excreted in the urine. The P women tended to excrete more zinc in their urine than the NP women (900 micrograms/day vs. 650 micrograms/day), but they excreted less zinc in their feces. The P women demonstrated a greater apparent zinc retention than the NP women (1.9 +/- 0.6 vs. 0.9 +/- 0.5 mg/day). This difference, however, was not statistically significant (P greater than 0.05).