Calcium and zinc retention from protein hydrolysate formulas in suckling rhesus monkeys.

Abstract

To determine calcium and zinc retention from infant formulas based on protein hydrolysates. Randomized, crossover. Newborn nursery at the California Primate Research Center, Davis. Suckling infant rhesus monkeys (N = 7), aged 6 weeks at the beginning of the study. Each infant received seven different formulas. Fasted infant monkeys were fed diets radiolabeled with calcium 47 and zinc 65. Retention was determined by counting whole body radioactivity immediately after dosing and 7 days after dosing. Retention of 47Ca was a mean (+/- SEM) of 79% +/- 4% from casein hydrolysate and 72% +/- 6% from the whey protein hydrolysate formula. Calcium 47 retention from hydrolysates based on whey protein/casein mixtures (a ratio of 60:40 or 50:50) was similar despite differences in protein sources and calcium content. Calcium 47 retention from two types of soy/collagen hydrolysate formula was found to be 68% +/- 6% and 59% +/- 4%, respectively, which is significantly lower than retention from casein hydrolysate. Considering the different calcium content of these formulas, total calcium retention from milk protein hydrolysates was higher than from soy/collagen products. Retention of 65Zn from milk protein hydrolysates ranged from 18% +/- 3% to 29% +/- 4% and was higher than that from soy/collagen formulas with a mean retention of 7% +/- 3% and 10% +/- 4%, respectively. Despite these differences in 65Zn retention, total zinc retention from all soy/collagen formulas was similar due to their higher zinc content. Calcium and zinc bioavailability was high from formulas based on milk protein hydrolysate, but was considerably lower from soy hydrolysates. Higher levels of calcium and zinc provided in soy hydrolysate formula compensated for the lower bioavailability and resulted in similar amounts of calcium and zinc retained.