The objective of this study is to compare the quantity of Zn absorbed from an accurately weighed quantity (~100 g) of minimally milled control maize (~15 µg Zn/g maize), from biofortified maize (~30 µg Zn/g) and from the same control maize that has been fortified (total level of ~60 µg Zn/g) when fed to young children age 24-36 months whose major habitual food staple is maize.

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.

Inclusion Criteria:

• Children age 24 to 36 months
• Maize meal accounts for at least 75% energy intake
• Able to consume 100 g maize flour/day
• Clinically healthy (stunting is acceptable)
• Lives in target community

Exclusion Criteria:

• Children with chronic or other known chronic disease
• If children are receiving zinc-fortified products, these products will need to be withheld for 2 weeks prior to the study