Confirmation of calcium absorption and femoral utilization in spontaneously hypertensive rats fed casein phosphopeptide supplemented diets

Abstract

Caseinophosphopeptides (CPP) have been shown to enhance calcium solubility and absorption from ligated segments of rat small intestine but there are few data in regard to the effect on calcium balance and utilization. This study evaluated the effect of supplementing casein and soy diets with CPP on FER, in situ paracellular calcium absorption, 24 hr calcium balance and mineralization in spontaneously hypertensive rats (SHR). Two principal phosphopeptides, α en-(1–21) and β-(1–25) casein were identified in the CPP by peptide sequencing following isolation by HPLC. Animals were fed 20% casein, and soy protein isolate diets, as well as casein and soy protein diets supplemented with 3% CPP. Animals fed CPP-soy protein diets exhibited an improved (P<0.05) FER, compared to soy fed counterparts. Soluble 45Ca and absorption from the ligated loop were also significantly (P<0.05) greater in animals fed the CPP supplemented soy diet, albeit calcium balance was not altered. The 24 hr balance study also indicated greater urinary Ca excretion in CPP-casein fed animals which resulted in a similar Ca balance to casein, soy and CPP-soy fed animals. Femur ash weight and Ca content were lower in soy fed animals and not significantly improved in animals fed diets supplemented with CPP. A similar response in femur bending failure energy was observed in animals fed soy and CPP-soy diets. Animals fed soy diets also exhibited relatively lower Mg apparent absorptions and femoral Mg content than counterparts fed the casein diet, however these differences were not significant. These results indicate that CPP-supplementation of soy diets although enhancing calcium solubility and paracellular absorption in situ, had little effect on apparent absorption and utilization in rats with an adequate calcium intake.