Availability of zinc: Loading tests with human milk, cow's milk, and infant formulas

Extract: Uptake of zinc with human milk, cow's milk and 4 infant formulas was investigated using a standard zinc loading test. Female subjects consumed 25 mg of zinc with the milk or formula, the amount of which was calculated to provide 5 gm of protein, after an 8-hour fast. Blood samples were taken prior to (base line) and at 30-minute intervals for 3 hours after consumption of zinc. Plasma zinc response was calculated as the area under the curve of change in plasma zinc from the base line value, plotted against time over 3 hours. The plasma response with human milk was significantly greater than with cow's milk and all the formulas. The response with cow's milk and a cow's milk-based formula was one-third that with human milk; responses with a soy-based and 2 casein hydrolysate-based formulas were lower. The results suggest that the bioavailability of zinc with human milk is better than with cow's milk or infant formulas. (author)