The effect of lactose on the intestinal absorption of calcium and zinc in the rat during maturation

Lactose facilitates the intestinal absorption of several minerals and trace elements in postweanling rats. There is no information in the literature on the effect of lactose on the process of absorp-tion in suckling rats. Because soy and elemental formulas are nonlactose-containing diets, the role of lactose in facilitating the intestinal absorption of minerals is of considerable nutritional importance. We studied therefore, the effect of water (control), lactose, sucrose, and glucose on the intestinal absorption and tissue uptake of calcium and zinc in the suckling (14-15 day old) and adolescent (42-43 day old) rats. Our results indicate that absorption of calcium and zinc was significantly greater in the suckling than in adolescent rats (P < 0.01). Lactose enhanced significantly the absorption and tissue uptake of calcium and zinc in the adolescent rats compared to control and other sugars. In the suckling rats lactose had no effect on the intestinal absorption or tissue uptake of calcium and zinc compared to control and other sugars. The possible mechanism(s) responsible for our findings are discussed. Speculation: Lactose enhances the intestinal absorption of minerals in the adolescent but not in the suckling rat. This finding may be related to differences in the permeability of the intestinal membranes, which occurs during maturation.