Submitted to: American Journal of Clinical Nutrition
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/7/2005
Publication Date: 1/1/2006
Citation: Mazariegos, M., Solomons, N.W., Hambidge, M.K., Krebs, N.F., Westcott, J.E., Sian, L., Campos, R., Barahona, B., Raboy, V. 2006. Zinc absorption in guatemalan school children fed normal or low-phytate maize. American Journal of Clinical Nutrition. v 83 p 59-64 Interpretive Summary: Low-income populations around the world depend on cereals and legumes for a major part of their diet. These foods contain high levels of phytic acid, chronic consumption of which can contribute to zinc deficiency. Zinc deficiency has adverse effects on human health, especially for children and women of child-bearing age. In rural Guatemala maize is a major food. This study evaluated the zinc nutritional status of Guatemalan children that were consuming either maize with normal phytic acid content, or a “low-phytate” maize. No large effect, statistically significant difference in the absorption of zinc from the different diets were observed. This lack of a positive effect of dietary phytic acid reduction on zinc absorption could reflect the difficulty of measuring such an effect under the experimental conditions of a rural Guatemalan village, or could reflect the fact that the actual difference in consumption of phytic acid was less than predicted based on the differences in phytic acid in the maize types used in the study.
Technical Abstract: Background: Poor bioavailability of zinc from high-phytate diets is an important contributory factor to zinc deficiency in low-income populations. Objective: The objective of this study was to determine the effect on zinc absorption of consumption of low-phytate maize. Design: The participants were apparently healthy children in the Central Highlands of Guatemala. Sixty children (20 per group) were randomized to be fed only the low-phytate maize or one of two control maizes: the isohybrid wild-type or a local maize for a 10-wk period. During the final week, fractional absorption of zinc (FAZ) for all meals during one day was measured using zinc stable isotopes with a dual isotope ratio technique based on urine enrichment data. Results: Phytate intakes (mean ± SD) for low-phytate, wild-type and local maize groups were 1536 ± 563; 2056 ± 517 and 2253 ± 687 mg/d. Corresponding zinc intakes were: 8.6 ± 2.5; 8.1 ± 2.0 and 9.7 ± 2.6 mg/d and dietary phytate:zinc molar ratios were 18 ± 5; 26 ± 6 and 23 ± 5. Corresponding FAZs were: 0.32 ± 0.07; 0.28 ± 0.07 and 0.29 ± 0.06. Total absorbed zincs (TAZ) were 2.7 ± 0.9; 2.3 ± 1.0 and 2.8 ± 1.0 mg/d. There were no significant differences among maize groups for either FAZ or TAZ. Conclusion: The absence of a significant increase in zinc absorption may be attributable to the unexpectedly limited reduction in dietary phytate and phytate:zinc molar ratio achieved with the low-phytate maize.