ZINC AND MANGANESE BIOAVAILABILITY FROM HUMAN-MILK AND INFANT FORMULAUSED FOR VERY-LOW-BIRTH-WEIGHT INFANTS, EVALUATED IN A RAT PUP MODEL

The bioavailability of zinc and manganese from diets used for very low birthweight infants was investigated in a rat pup model using radiois otopes. The effect of protein source and content and of pasteurization was evaluated, and two different approaches for evaluation of zinc an d manganese bioavailability in the rat pup model were compared. Zinc a nd manganese bioavailability from the studied human milk and infant fo rmula for very low birthweight infants was high. Liver uptake of Zn-65 from labeled premature infant diets in sucklings rat pups was 26-29%, and absorption calculated as the difference between administered dose and nonabsorbed activity 6 h after oral intubation was 93-95%. Retent ion of manganese calculated as the sum of Mn-54 retained by organs and carcass was 85-95% from human milk and premature infant formula, and absorption calculated from nonabsorbed activity was 83-88% after 6 h. Fortification of early human milk significantly increased the bioavail ability of zinc. No effect of pasteurization of human milk was found o n zinc or manganese bioavailability. Liver zinc uptake was found to be a more sensitive parameter than absorption for evaluation of diets wi th a high zinc bioavailability. Measurement of retained activity of ma nganese in carcass and organs was judged to be the preferred parameter for evaluation of diets with high manganese availability.