Effect of the ratio of casein phosphopeptides to calcium (w/w) on passive calcium transport in the distal small intestine of rats

OBJECTIVE: We investigated the influence of different ratios between casein phosphopeptides and calcium (CPP/Ca) in intestinal lumen on passive Ca transport across the distal small intestine of rats in vitro. METHODS: We measured the amounts of passive Ca absorbed across the everted distal small intestine of rats with the use of radioactive Ca-45 as tracer. Four CPP/Ca ratios (5, 10, 15, and 20 w/w) and three mineral concentrations (4, 8, and 12 mmol/L) were tested on groups of six rats. RESULTS: We found a significant effect of the CPP/Ca ratio on mineral absorption (p < 0.001). The amounts of Ca absorbed increased from a ratio of 5 to a ratio of 15 and decreased with a ratio of 20, with a similar trend for every concentration tested. The more evident effect was found with the concentration of 12 mmol/L of Ca (P < 0.001 to 0.05). CONCLUSION: The positive effect of CPPs on passive Ca absorption seems to depend on the relative amounts of both species in intestinal lumen. In this study, the ratio 15 was identified as the most efficient at increasing mineral transport. This evidence might be considered before suggesting CPP as a Ca dietary integrator, although more studies in vitro and in vivo are needed. (C) Elsevier Science Inc. 2002.