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.