Effect of phytase on zinc absorption from a millet-based porridge fed to young Burkinabe children

Abstract

Fortifying cereal staples with zinc is a strategy for increasing zinc intake in young children in developing countries. However, phytic acid (PA) naturally present in cereals strongly decreases zinc absorption. A stable-isotope zinc absorption study was conducted in young children to investigate the ability of the PA-degrading enzyme phytase to improve zinc absorption, when added to a cereal porridge immediately before consumption. Fractional absorption of zinc (FAZ) was estimated in 35 young healthy Burkinabe children using the double-isotopic tracer ratio method with 67Zn as oral tracer and 70Zn as intravenous tracer, in a crossover design. The test meals were: (a) a millet-based porridge containing 1.4 mg total zinc (native plus 1 mg added as ZnSO4) with a PA:Zn molar ratio of 7.7; (b) the same porridge with the enzyme phytase (20.5 phytase units (FTU)) added immediately before consumption. The exchangeable zinc pool (EZP) was determined as a potential measure of long-term zinc intake in 20 of the 35 children and compared with FAZ. Mean FAZ increased from 9.5±3.4 to 16.0±5.1% (P<0.0001), when phytase was added to the meal. The mean EZP was 3.6±0.5 mg/kg. There was no correlation between the EZP and FAZ values for either of the two test meals. Adding phytase immediately prior to consumption of a zinc-fortified cereal-based complementary food can improve zinc absorption in young children.