Participating children were randomized to receive an accurately weighed quantity of \~100g/day of either the control, fortified or biofortified study maize for 1 day.
On day 1, mothers brought their child to the health center before breakfast. All meals were extrinsically labeled with a zinc stable isotope (70Zn). Meals on this day were consumed in the presence of the research staff. The quantities of nshima or porridge prepared and eaten were accurately weighed and duplicate meals were collected for subsequent mineral analyses.
Between lunch and dinner on day 1 at the Health Center, a blood sample was collected for Hb and plasma Zn analyses and, immediately after and through the same needle, a stable isotope of zinc was intravenously administered into a forearm vein over 1-2 minutes. The family then returned home.
Morning spot urine samples were collected twice daily starting on day 5 and continuing through day 8. Once these collections were finished, the study for this child was complete.
Dietary Zn was measured from laboratory assays of the duplicate test meals. Fractional absorption of Zn (FAZ) was measured by dual isotope tracer ratio methods in urine. Absorbed Zn was calculated by multiplying dietary Zn by FAZ.
