Effect of casein phosphopeptides on zinc and calcium absorption from bread meals

Animal studies suggest that casein phosphopeptides (CPP), formed by proteolytic digestion of casein, have a positive effect on Ca availability. The aim of this study was to investigate the ability of CPP to improve Zn and Ca absorption from phytate-containing bread meals. Secondly, it was tested whether the Ca content of the meal influenced the effect of CPP on Zn absorption from a high-phytate meal. Zn and Ca absorption from single model meals was determined by extrinsic labeling with 65Zn and 47Ca and measurement of whole-body retention. Thirty-one healthy adults (19-30 y) divided into three groups received one of three meal types based on white-wheat rolls with different phytate and Ca content: A: low-phytate/high-Ca (n = 10), B: high-phytate/high-Ca (n = 10) and C: high-phytate/low-Ca (n = 11). Each individual received the same meal type at three different occasions with 0, 250 and 1000 mg CPP added. CPP had no effect on Zn absorption: A: 14.3 +/- 4.4% (mean +/- SD) (0 mg CPP), 16.7 +/- 6.6% (250 mg CPP) and 16.0 +/- 8.8% (1000 mg CPP); B: 7.0 +/- 1.6%, 7.7 +/- 3.0% and 8.0 +/- 2.6%; C: 7.7 +/- 2.5%, 7.0 +/- 2.3% and 6.5 +/- 1.6%, respectively. Addition of 1000 mg CPP reduced fractional Ca absorption from meal A: 33.8 +/- 7.1%, 30.5 +/- 6.3% and 25.9 +/- 8.7% (p < 0.05), whereas CPP had no effect in meal B: 29.3 +/- 8.3%, 27.0 +/- 7.4% and 27.6 +/- 11.0%. However, the absolute quantity of Ca absorbed was unaffected. In conclusion, Zn and Ca absorption from these meals were not significantly influenced by the addition of CPP, Ca addition could not explain the failure of CPP to improve Zn absorption.