Calcium and zinc retention from protein hydrolysate formulas in suckling rhesus monkeys
S. Rudloff and B. Lonnerdal
Department of Nutrition, University of California, Davis 95616.
OBJECTIVE--To determine calcium and zinc retention from infant formulas
based on protein hydrolysates. DESIGN--Randomized, crossover.
SETTING--Newborn nursery at the California Primate Research Center, Davis.
PARTICIPANTS--Suckling infant rhesus monkeys (N = 7), aged 6 weeks at the
beginning of the study. Each infant received seven different formulas.
INTERVENTIONS--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.
MEASUREMENTS AND RESULTS--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. CONCLUSIONS--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.
