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Background: Calcium fortification of maize has been achieved for millennia in Central America by the process of nixtamalization. Bioavailability of calcium is, however, compromised by phytate, which is present in large quantities in maize kernels and is only modestly reduced by nixtamalization. Objective: The objective was to compare the absorption of calcium from tortilla meals prepared from low-phytate maize with that from meals prepared from maize with typical phytate content. Design: At 1-mo intervals, 5 healthy adult women were fed 2 test meals of [approximately equal to] 140 g tortillas in lieu of breakfast. On one occasion, the tortillas were prepared from maize with [approximately equal to] 60% phytate reduction, and, on the other occasion, they were prepared flora the matching isohybrid wild-type maize. Beginning midway through the test meal, [44.sup.C]a (0.3 mg/kg body wt) was administered in water as an extrinsic label; [42.sup.C]a (0.06 mg/kg body wt) was administered intravenously immediately after the test meal. Isotope ratios of [42.sup.C]a to [43.sup.C]a and of [44.sup.C]a to [43.sup.C]a were measured by inductively coupled plasma mass spectrometry in urine collected as an 8-h pool from the period 16-24 h after intravenous tracer administration and prepared by the oxalate precipitation method. Fractional absorption of calcium was determined by using a dual-isotope ratio technique. Results: Mean fractional absorption of calcium from tortillas prepared from the low-phytate maize (0.50 [+ or -] 0.03) was significantly (P = 0.003) greater than that from tortillas prepared from the control maize (0.35 [+ or -] 0.07). Conclusion: The increase in the quantity of calcium absorbed could be of practical importance for calcium nutriture when the intake of dairy products is limited. KEY WORDS Maize, phytate, low-phytate maize alleles, tortillas, calcium absorption

Background: Corn masa flour is widely consumed in Central America and is therefore a potentially useful vehicle for iron fortification. Objective: The goal was to evaluate the bioavailability of iron from meals based on corn tortillas and black bean paste that were fortified with ferrous fumarate, ferrous sulfate, or NaFeEDTA and to investigate the potential of [Na.sub.2]EDTA to increase the bioavailability of iron from ferrous fumarate. Design: With use of a crossover study design, iron bioavailability was measured in Guatemalan girls aged 12-13 y by a stable-isotope technique based on erythrocyte incorporation 14 d after intake. Results: Geometric mean iron bioavailability from test meals fortified with ferrous fumarate was 5.5-6.2% and was not improved significantly by the addition of [Na.sub.2]EDTA at molar ratios of 1:1 relative to fortification iron or to the total iron content of the fortified corn masa flour. Geometric mean iron bioavailability from test meals fortified with ferrous sulfate was 5.5% and was significantly higher in test meals fortified with NaFeEDTA (9.0%; P = 0.009, paired t test). Conclusions: The bioavailability of iron from ferrous fumarate was not improved by the addition of [Na.sub.2]EDTA, contrary to what was previously shown for ferrous sulfate in other cereal-based meals. However, the bioavailability of iron from the test meal was significantly enhanced when NaFeEDTA replaced ferrous sulfate. These results support the use of NaFeEDTA in the fortification of inhibitory staple foods such as corn masa flour. Am J Clin Nutr 2002;75:535-9. KEY WORDS Iron bioavailability, stable isotopes, ferrous fumarate, corn tortillas, [Na.sub.2]EDTA, disodium ethylenediaminetetraacetate, NaFeEDTA, sodium iron ethylenediaminetetraacetate, girls, Guatemala, corn masa flour