Dietary conditions influencing relative zinc availability from foods to the rat and correlations with in vitro measurements

Zinc availability from a series of foods was determined using 65Zn-labeled test meals fed to rats. Zinc availability relative to zinc chloride depended on the amount of the zinc source in the test meal. Zinc availability from several foods was similar to that from zinc chloride when tested in smaller amounts, but enhanced when fed in larger amounts. The range of zinc availability was similar for foods of plant and animal origin. Rats retained significantly more zinc from pork, chicken, peanut butter, egg or milk than from rice, beef, soybean flour or navy beans. Foods with intermediate zinc availability were sweet corn, whole wheat bread, cheese and oysters. Several food characteristics were examined for possible relationships with zinc availability, including the solubility or molecular size of zinc compounds after an in vitro enzymatic digestion and the contents of phytic acid, minerals, amino acids, carbohydrate and fatty acids relative to the zinc content of the food. Protein and several amino acids predicted about half of the variance in zinc availability. Following in vitro enzymatic digestion, neither zinc solubility nor the partitioning of zinc between low and high molecular weight substances was a strong predictor of zinc availability.