Absorption of zinc from dietary casein phosphopeptide complex with zinc in rats given a soybean protein-based diet

The absorption of zinc (Zn) in the form of casein phosphopeptide (CPP) complex was compared with that of its chloride form in rats given a soybean protein-based diet. We prepared 67Zn complex with CPP (67Zn-CPP). Male rats were given a diet containing ZnCl2 in the preliminary period. After overnight food deprivation, they were fed a test meal labeled 67Zn-CPP or 67ZnCl2 (4 g Zn-free diet + 0.12 mg 67Zn) with 0.5 mg Dysprosium (Dy) as a fecal marker. Feces were collected for 5 d and analyzed for 67Zn isotopic enrichment and Dy concentration with an inductively coupled plasma mass spectrometer. Fecal Dy excretion closely paralleled that of 67Zn, and more than 89% of the administered Dy was recovered in the feces collected for 5 d. Moreover, the Zn source did not affect the excretion pattern of 67Zn. Since Dy and 67Zn were almost excreted within 3 d after the administration, the apparent absorption of 67Zn was calculated from the pooled data for 3 d. The source of Zn did not affect the apparent absorption of 67Zn. These results suggested that dietary Zn in the form of CPP complex did not show higher absorbability in rats.