Effect of genetically modified, low–phytic acid maize on absorption of iron from tortillas

Abstract

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the phytic acid content of foods by genetically modifying their capacity to synthesize phytic acid (4; V Raboy et al, unpublished observations, 1994).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without affecting the total phosphorus content of the grain or the health of the plant (V Raboy, K Young, P Gerbasi, unpublished observations, 1994).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 ...

Effects of aqueous soaking on the phytate and mineral contents and phytate:mineral ratios of wholegrain normal sorghum and maize and low phytate sorghum

“…The mineral contents of the WS and WM grains (Table 6) were similar to previously reported values for sorghum: P (FAO, 1995;Glew et al, 1997), Fe (FAO, 1995Matuschek ,t al., 2001), Zn (FAO, 1995), Ca (FAO, 1995Kruger et al, 2013) and Mg (FAO, 1995;Glew et al, 1997), and maize: P (FAO, 1992;Spencer et al, 2000), Fe (FAO, 1992;Umeta et al, 2005), Zn (FAO 1992;Beiseigel et al, 2007;Mendoza et al, 1998;), Ca (FAO, 1992Mendoza et al, 2001;) and Mg (FAO, 1992;Mendoza et al, 2001). However, the mineral contents of the RTS and RNTS were higher than the reported ranges for sorghum.…”

The Maize Low-Phytic Acid Mutant lpa2 Is Caused by Mutation in an Inositol Phosphate Kinase Gene

“…Low-phytic acid grain and legume in feed could reduce phosphorus pollution to environment and reduce amount of phosphorus supplementation required in animal feeds (Ertl et al, 1998). Such grain would also offer more available Fe and Zn for human nutrition (Mendoza et al, 1998).Low-phytic acid mutants have been generated by mutagenesis in maize, rice, barley, and soybean (Rasmussen and Hatzack, 1998;Larson et al, 2000;Raboy et al, 2000;Wilcox et al, 2000) and used in genetic breeding (Raboy et al, 2001). Two types of recessive mutants affecting seed phytic acid are known.…”

“…Low-phytic acid grain and legume in feed could reduce phosphorus pollution to environment and reduce amount of phosphorus supplementation required in animal feeds (Ertl et al, 1998). Such grain would also offer more available Fe and Zn for human nutrition (Mendoza et al, 1998).…”

Variability in phytic acid content in barley grain.

“…V lidské výživě je nutné posuzovat roli PA ze dvou hledisek -jako silný antioxidant snižuje riziko vzniku civilizačních chorob a v podobě prekursoru derivátu inositolu plní vý-znamné fyziologické funkce. Na druhé straně je jednou z význam-ných příčin deficience železa a zinku ve stravě a zejména v oblastech s převahou potravin ve formě obilovin a luštěnin hlavní příčinou minerálních malnutricií (Manary et al, 2000;Mendoza et al, 1998). Fytátový fosfor se navíc spolu s odpady při výkrmu drůbeže, prasat a ryb stává významným zdrojem znečištění povrchových vod (Raboy, 2001), a tedy životního prostředí.…”