The quantity of zinc absorbed from wheat in adult women is enhanced by biofortification

Abstract

Biofortification of crops that provide major food staples to large, poor rural populations offers an appealing strategy for diminishing public health problems attributable to micronutrient deficiencies. The objective of this first-stage human study was to determine the increase in quantity of zinc (Zn) absorbed achieved by biofortifying wheat with Zn. Secondary objectives included evaluating the magnitude of the measured increases in Zn absorption as a function of dietary Zn and phytate. The biofortified and control wheats were extracted at high (95%) and moderate (80%) levels and Zn and phytate concentrations measured. Adult women with habitual diets high in phytate consumed 300 g of 95 or 80% extracted wheat as tortillas for 2 consecutive days using either biofortified (41 mg Zn/g) or control (24 mg Zn/g) wheat. All meals for the 2-d experiment were extrinsically labeled with Zn stable isotopes and fractional absorption of Zn determined by a dual isotope tracer ratio technique. Zn intake from the biofortified wheat diet was 5.7 mg/d (72%) higher at 95% extraction (P < 0.001) and 2.7 mg/d (68%) higher at 80% extraction compared with the corresponding control wheat (P = 0.007). Zn absorption from biofortified wheat meals was (mean +/- SD) 2.1 +/- 0.7 and 2.0 +/- 0.4 mg/d for 95 and 80% extraction, respectively, both of which were 0.5 mg/d higher than for the corresponding control wheat (P < 0.05). Results were consistent with those predicted by a trivariate model of Zn absorption as a function of dietary Zn and phytate. Potentially valuable increases in Zn absorption can be achieved from biofortification of wheat with Zn.

FIGURE 1

Consort diagram depicting randomization scheme.

FIGURE 2

Two-dimensional plot of measured absorption data and prediction curves derived from a trivariate model of Zn absorption as a function of dietary Zn and phytate intake (5). Prediction curves for the mean daily phytate intakes of each of the 4 conditions are shown. The zero phytate curve is provided for reference. Also shown are the mean ± SD measured Zn absorptions for each of the 4 study women who consumed 95% (n = 14) or 80% (n = 13) extracted control and Zn-biofortified wheat. In each case, the measured absorption agreed very well with the model's prediction (Table 1).