Upregulation of zinc absorption matches increases in physiological requirements for zinc in women consuming high-or-moderate-phytate diets during late pregnancy and early lactation

Authors: HAMBIDGE, K.MICHAEL - University Of Colorado; MILLER, LELAND - University Of Colorado; MAZARIEGOS, MANOLO - Instituto De Nutrición De Centroamérica Y Panamá (INCAP); WESTCOTT, JAMIE - University Of Colorado; SOLOMONS, NOEL - Center For Studies Of Sensory Impairment, Aging And Metabolism (CESSIAM); Raboy, Victor; KEMP, JENNIFER - University Of Colorado; DAS, ABHIK - Research Triangle Institute; GOCO, NORMAN - Research Triangle Institute; HARTWELL, TY - Research Triangle Institute; WRIGHT, LINDA - National Institutes Of Health (NIH); KREBS, NANCY - University Of Colorado

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/17/2017
Publication Date: 4/19/2017
Citation: Hambidge, K.M., Miller, L.V., Mazariegos, M., Westcott, J., Solomons, N.W., Raboy, V., Kemp, J.F., Das, A., Goco, N., Hartwell, T., Wright, L., Krebs, N.F. 2017. Upregulation of zinc absorption matches increases in physiological requirements for zinc in women consuming high-or-moderate-phytate diets during late pregnancy and early lactation. Journal of Nutrition. doi: 10.3945/jn.116.245902.

Interpretive Summary: Zinc deficiency is a substantial world-wide public health problem that can greatly impact both maternal and infant health. A greater understanding of the physiology of zinc nutrition and deficiency during pregnancy and lactation is required to enhance efforts to deal with this important problem. One factor that impacts the nutritional quality of foods relative to their zinc bioavailability is their seed-derived phytic acid content. In this study volunteers consumed foods prepared with “normal phytic acid” maize or with “low-phytic acid” maize. Analyzes of the amount of zinc absorbed by pregnant women from their diets during various stages of pregnancy and lactation revealed that during late pregnancy and lactation there is an up-regulation of zinc absorption by women such that dietary phytic acid has less of a negative impact on zinc nutritional status. These results advance our understanding of the physiology of zinc nutrition during pregnancy and lactation and advances our knowledge of the impact or lack thereof of dietary phytic acid on women and infants. It will thus assist the nutritional science and public health communities in developing approaches to and addressing concerns over zinc deficiency and dietary phytic acid.

Technical Abstract: Objectives: To determine the roles of host and dietary factors in matching increases in physiological requirements for zinc (Zn) during late pregnancy and early lactation in women whose major dietary staple is maize with and without phytate reduction. Methods: Subjects were 22 indigenous Guatemalan women participating in a larger study in which subjects whose major food staple was maize. Women were randomly assigned to one of two ad lib feeding groups, low phytate maize (LP, 80% reduction, n=14) or control maize (C, n=8), and completed Zn absorption studies at 8 (phase 1) and 34 (phase 2) wk gestation and 2 (phase 3) and 6 (phase 4) mo lactation. Total dietary Zn (TDZ, mg/d) was determined from duplicate diets; fractional absorption of Zn (FAZ) by a dual isotope ratio technique; total absorbed Zn (TAZ, mg Zn/d) = TDZ x FAZ. Dietary phytate intake mg/d (TDP) was measured by a FeCl3 precipitation method. Data interpretation included comparison of phase-specific TAZ with dietary Zn and phytate model-based predictions. Results: The inhibitory effect of phytate on TAZ is evident across pregnancy. However, TAZ in late pregnancy and early lactation are greater than predicted for the same intakes of Zn and phytate in non-pregnant/non-lactating (NPNL) subjects. Consequently, the TDZ necessary to absorb adequate Zn to meet the physiological requirements in phases 2 and 3 is less than that predicted for NPNL women with the same dietary phytate intake as the LP and C groups. Conclusions: These results are consistent with up-regulation of Zn absorption in late pregnancy and early lactation with diminution of phytate inhibition and which parallel increases in physiological requirements.