Bioavailability of zinc in infant cereals

The bioabailability of zinc in three cereals was determined by a rat assay, using total femur zinc as the indicator. The basal diet contained 25% egg white solids and 0.6 microgram zinc per gram. The infant cereals were included in the diets at three graded levels to supply 3--12 microgram zinc per gram. Zinc sulphate was used as a standard source, with and without supplemental iron (185, 370, 555 microgram/g, respectively) at 3, 6 and 9 microgram zinc per gram with a view to determine the effect of excess iron on zinc availability. Added iron from sodium iron pyrophosphate was not found to have any effect on the bioavailability of zinc from zinc sulphate. The responses for the three cereals were linear but the regression lines representing them and the standard source did not have a common intercept. However, the ratio of the slope of the regression line for the test source to that of the standard indicated that the cereal containing soy protein was a better source of zinc (ratio = 0.49) than the barley cereal (9.10) or the rice cereal (0.32). These ratios did not show any correlation with the actual iron-precipitable phytate phosphorus content or the reported crude fibre content.