Dietary phytate reduction improves zinc absorption in Malawian children recovering from tuberculosis but not in well children

High dietary phytate content that compromises zinc nutriture is thought to be a major problem among children of the developing world. Zinc stable isot ope techniques permit the quantitative assessment of the effect of phytate reduction on zinc homeostasis. We tested the hypothesis that zinc absorptio n would be increased in Malawian children fed a reduced-phytate corn-plus-s oy diet compared with a standard high phytate diet. Twenty-three children h ospitalized in Blantyre, Malawi, were enrolled. Children were selected from those recovering from tuberculosis and from well children (those with mino r injuries, those awaiting elective surgery or healthy siblings). Children received a diet of corn-plus-soy porridge (either low phytate or high phyta te) for a period of 3-7 d and then participated in a zinc stable isotope st udy. The study included the administration of oral and intravenous zinc sta ble isotopes and 7-d collections of urine and stool. The diet was maintaine d throughout the duration of specimen collection. Zinc isotopic enrichments in urine and stool were measured, and zinc fractional absorption, total zi nc absorption, endogenous fecal zinc, net zinc retention and size of the ex changeable zinc pool were calculated. Among the 14 children recovering from tuberculosis, dietary phytate reduction resulted in higher fractional abso rption (0.41 +/- 0.14 versus 0.24 +/- 0.09, mean +/- 10 SD, P < 0.05) and t otal zinc absorption (169 +/- 55 versus 100 +/- 46 <mu>g/(kg d), P < 0.05). No effect of phytate reduction was seen in the well children (n = 9). Phyt ate reduction did not decrease the absolute endogenous fecal zinc, but it d id decrease it relative to total absorbed zinc. These preliminary results i ndicate that phytate reduction may be beneficial in improving zinc nutritur e in groups with increased zinc requirements who consume a cereal-based die t.