Background: Genetically modified, low-phytic acid strains of maize were developed to enhance mineral absorption, but have not been tested previously in humans. Objectives: We evaluated the mineral and phytic acid contents of a low-phytic acid "flint" maize (LPM, the lpa-1-1 mutant) and its parent, wild-type strain (WTM) and measured iron absorption from tortillas prepared with each type of maize and from a reference dose of ferrous ascorbate. Design: Proximate composition and mineral and phytic acid contents were measured by standard techniques. Iron absorption from tortillas was evaluated by using the extrinsic tag method and was measured as the incorporation of radiolabeled iron into the red blood cells of 14 nonanemic men 2 wk after intake. Results: The phytic acid content of LPM was 3.48 mg/g, Ϸ35% of the phytic acid content of WTM; concentrations of macronutrients and most minerals were not significantly different between strains. Iron absorption results were adjusted to 40% absorption of ferrous ascorbate. Iron absorption was 49% greater from LPM (8.2% of intake) than from WTM (5.5% of intake) tortillas (P < 0.001, repeated-measures analysis of variance). Conclusion: Consumption of genetically modified, low-phytic acid strains of maize may improve iron absorption in human populations that consume maize-based diets.Am J Clin Nutr 1998;68:1123-7. KEY WORDSIron, iron absorption, iron deficiency, phytic acid, corn, maize, tortilla, men INTRODUCTIONNonheme iron from cereals and other plant sources is poorly absorbed because of the presence of inhibitors of iron absorption, such as phytic acid, tannins, and selected dietary fibers, which irreversibly bind iron in the intestinal lumen (1-3). One possible approach to improving iron absorption is to reduce the phytic acid content of foods by genetically modifying their capacity to synthesize phytic acid (4; V Raboy et al, unpublished observations, 1994). Recent experiments indicate that much of the phytic acid in maize and other cereals can be removed through genetic engineering without affecting the total phosphorus content of the grain or the health of the plant (V Raboy, K Young, P Gerbasi, unpublished observations, 1994). This offers great promise for human trace mineral nutrition, especially in populations that are primarily dependent on plantderived diets.Before promoting the large-scale production of low-phytic acid grain for human consumption, it is necessary that we determine whether a reduction in phytic acid content affects other components of the grain and whether low-phytic acid mutants do indeed have the expected effect on mineral absorption from mixed diets consumed by humans. We therefore conducted several laboratory analyses of the nutrient content of low-phytic acid and unmodified strains of maize and completed a clinical study of the effect of substituting the low-phytic acid maize on the absorption of nonheme iron from maize tortillas. The studies were conducted with maize tortillas because this is the most common form in which maize is ...

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Summary The reduction of phytic acid content in grains by genetic manipulation is a novel approach to increase mineral absorption from food based diets. Low phytic acid corn (Zea mays), rice (Oryza sativa), barley (Hordeum vulgare) and soybean (Gycine max) genotypes have been generated and mineral absorption has been evaluated. Genetically modified low phytic acid plants could be a novel contribution to the reduction of micronutrient malnutrition and animal waste phosphorus. Nevertheless, additional research needs to be done to understand the molecular biology and genetics of phytic acid accumulation during seed development, the negative and positive roles of dietary phytic acid in human health and the feasibility and effectiveness of the sustainable implementation of this approach at the community level.