Effect of caseinphosphopeptides on inhibition of calcium intestinal absorption due to phosphate

Caseinphosphopeptides (CPPs) are peptides resulting from enzyme digestion of whole casein, characterized by the presence of an aminoacid cluster, negatively charged at physiological intestinal pH, that binds cations. The aim of the present study was to compare Ca absorption through the everted small intestine of rats from CaCl2 or Ca-CPPs solutions, in absence of inorganic phosphate (Pi) or when two ratios between Ca and Pi occur. Secondly, it was evaluated whether the ion absorption could be affected by the fatty acid pattern of enterocyte membrane. Results showed that in the absence of Pi, Ca transport from CaCl2 was higher than from Ca-CPPs solutions. However, when Pi was added to the CaCl2 solution, Ca absorption decreased by 90% (Ca:Pi = 1:1) and 97% (Ca:Pi = 1:2). On the contrary, when Pi was added to the Ca-CPPs solution, Ca transport decreased only by 40% (Ca:Pi = 1:1) and 60% (Ca:Pi = 1:2). The enrichment of enterocyte membrane with n-3 fatty acids (fish oil diet) compared to control diet did not modify the effect of CPPs on Ca transport in ileum of rats. These findings demonstrate that CPPs can limit the inhibitory effect of phosphate on Ca availability and increase Ca transport across the distal small intestine. This action could be of nutritional relevance especially when the dietary intake of this mineral is lower than the recommended level or there is an unbalanced ratio Ca/Pi in diet.