Effect of dietary zinc sources and pregnancy on zinc utilization in adult women fed controlled diets.

Five nonpregnant and 10 pregnant women participated in 21-day confined metabolic studies. Two diets each providing 16 mg of zinc per day were fed. In one diet 70% of the total zinc was provided by animal products and 30% was contributed by plant sources. In the second diet the proportions were reversed. Apparent absorption of zinc was determined using the balance technique. During the last 15 days of the study, zinc intake was only slightly greater than the amount of zinc excreted in feces. Mean apparent absorption values did not exceed 5% and did not vary due to diet or pregnancy. Zinc bioavailability was also assessed by measuring the apparent absorption of a stable isotope of zinc (70Zn) added to the diet. There was no significant effect of either diet or pregnancy on 70Zn absorption, which averaged about 25%. Serum zinc values were normal throughout the study and did not change significantly as a function of diet. The pregnant women, however, maintained values that were 19-27% lower than those of the nonpregnant women. In summary, the substitution of animal sources of zinc by plant products did not reduce zinc bioavailability or alter zinc utilization.