Marianne Hansen

The effect of casein phosphopeptides on zinc and calcium absorption from high phytate infant diets assessed in rat pups and Caco-2 cells.

Milk and other foods of animal origin have been shown to improve zinc absorption from phytate-rich diets. The ability of milk proteins and casein phosphopeptides (CPP), the latter formed during digestion of casein, to overcome the inhibitory effect of phytate on zinc and calcium absorption was investigated. Suckling rat pups were given aqueous phytate-containing solutions, oat diet, or soy formula alone or with milk proteins or CPP added. Diets labeled extrinsically with 65Zn and 47Ca were given by gastric intubation. Absorption was determined from measurement of radioisotope activity in intestine, organs, and carcass. Addition of CPP improved zinc and calcium absorption from aqueous phytate-containing solutions and from oat diet. The effect of CPP on calcium absorption from soy formula was less pronounced. The influence of CPP on zinc absorption from aqueous phytate-containing solutions was also examined using a human colon carcinoma-derived cell line, Caco-2. Binding + uptake of 65Zn was determined after incubation with these solutions. Phytate reduced zinc binding+ uptake to 79% of the control value. Addition of 14 μmol of CPP/L increased zinc binding + uptake to 94%, whereas 36 and 72 μmol of CPP/L depressed zinc binding + uptake (75 and 39%). In conclusion, CPP improved zinc and calcium bioavailability from high phytate meals in the rat pup model. In the Caco-2 cell system, addition of 14 μmol of CPP/L showed a positive effect on zinc binding + uptake from phytate-containing solutions, whereas higher levels of CPP inhibited zinc binding + uptake.

Casein phosphopeptides improve zinc and calcium absorption from rice-based but not from whole-grain infant cereal

BACKGROUND Casein phosphopeptides (CPP) are phosphorus-rich peptide fragments of casein, assumed to contribute to the high bioavailability of calcium from milk. METHODS The effect of casein phosphopeptides on calcium and zinc absorption from infant foods was investigated. Twenty-two men and women were given single test meals extrinsically labeled with Ca and Zn. Absorption was calculated from measurements on whole-body retention of the radioisotopes. Each subject was given either rice-based cereal (n = 11) or whole-grain cereal (n = 11) on three occasions together with 250 ml water and added 0, 1, and 2 g CPP in random order. One serving of rice-based cereal contained 481 mg Ca and 1.29 mg Zn; whole-grain cereal contained 541 mg Ca and 1.77 mg Zn. One and 2 g of CPP contributed with additional 69 and 138 mg Ca, respectively. RESULTS From rice-based cereal, fractional calcium absorption was not affected by CPP addition (mean +/- SD): 16.0 +/- 4.0% (no CPP), 17.6 +/- 4.5% (1 g CPP), and 15.8 +/- 4.3% (2 g CPP), while the total quantity of calcium absorbed was significantly improved: 7 +/- 19 mg, 97 +/- 25 mg, and 98 +/- 26 mg, respectively (p = 0.0004). Fractional zinc absorption as well as total quantity of zinc absorbed were increased with addition of CPP: 19.4 +/- 9.0% (0.25 +/- 0.12 mg), 25.2 +/- 7.5% (0.33 +/- 0.10 mg) and 23.9 +/- 5.4% (0.31 +/- 0.07 mg) at the three CPP levels (p = 0.04). From whole-grain cereal, CPP had no effect on the percentage or actual quantity of calcium absorbed: 17.0 +/- 3.2% (92 +/- 18 mg), 17.2 +/- 4.5% (105 +/- 27 mg), and 15.0 +/- 4.6% (102 +/- 31 mg), respectively. Zinc absorption was also not influenced by CPP: 16.0 +/- 5.1% (0.28 +/- 0.09 mg), 15.3 +/- 3.1% (0.27 +/- 0.06 mg) and 18.1 +/- 4.4% (0.32 +/- 0.08 mg), respectively. CONCLUSIONS CPP addition improved calcium and zinc absorption from rice-based cereal, while no effect was seen from whole-grain cereal.