The objective of this study was to test the hypothesis that Zn requirements are met by appropriate stage of reproductive cycle regulation of total daily Zn absorption (TAZ) despite high dietary phytate.
Subjects were 17 indigenous Guatemalan women who completed longitudinal whole day Zn absorption (TAZ) studies in the home at 8 (Stage 1) and 34 (Stage 2) weeks gestation and at 2 (Stage 3) and 6 months lactation (Stages 4). Fractional absorption of Zn (FAZ) was determined by a dual isotope ratio technique and dietary Zn (TDZ) from duplicate diets; TAZ = TDZ x FAZ. Phytate intake was measured by FeCl3 precipitation.
Dietary Zn intake did not differ between stages; mean (SD) = 11.9 (3.7); 77% of dietary Zn was derived from tortillas. Mean FAZ varied between 0.24 in early pregnancy to 0.39 in early lactation and the TAZ ranged between 2.6 and 5.1 mg Zn/d. The trend is suggestive of phytate effect in TAZ for Stages 1 and 4, but not in Stages 2 and 3. Increase in TAZ in Stages 2 and 3 matched increase in physiological requirements.
These results may explain why clinical/epidemiological evidence of adverse maternal/offspring effects of apparently low Zn intakes of poorly bioavailable Zn are not observed consistently.