Zinc absorption from a low-phytic acid maize

Background: Phytic acid reduction in cereal grains has been accomplished with plant genetic techniques. These low-phytic acid grains provide a strategy for improving the mineral (eg, zinc) status in populations that are dependent on grains, including maize (Zea mays L.), as major dietary staples. Objective: The objective was to compare the fractional absorption of zinc from polenta prepared from maize low in phytic acid with that prepared from a wild-type isohybrid maize (control) after short-term consumption by adults whose habitual diet is low in phytic acid. Design: Healthy adults served as their own control subjects in a crossover design. All meals on 1 d consisted of polenta prepared from a low-phytic acid maize homozygous for the recessive low phytic acid 1-1 (lpa1-1). On the preceding or following day, all meals consisted of polenta prepared from a sibling isohybrid homozygous wild-type maize with a "normal" phytic acid content. The low-phytic acid maize contained approximate to60% less phytic acid than did the wild-type maize. All test meals were extrinsically labeled with zinc stable-isotope tracers. The fractional absorption of zinc was determined on the basis of fecal enrichment. Results: The molar ratios of phytic acid to zinc in the polenta prepared from lpa1-1 maize and the wild-type maize were 17:1 and 36: 1, respectively. The corresponding fractional absorptions of zinc were 0.30 +/- 0.13 and 0.17 +/- 0.11, respectively (P < 0.005). Conclusion: Substitution of a low-phytic acid grain in a maize-based diet is associated with a substantial increase in zinc absorption.