Absorption of nonheme iron in ascorbic acid-deficient rats

Prior studies have shown that the absorption of dietary nonheme iron in rats is much higher and less responsive to dietary variables than in human subjects. The aim of the present study was to determine whether this dissimilarity is explained by species differences in ascorbic acid status or metabolism. Iron absorption studies were performed with normal rats and with a genetic strain that lacks the ability to synthesize the vitamin. Ascorbic acid deficiency was produced in these animals by removing supplemental vitamin C from the diet for a brief period before the study. Iron absorption was measured from meals tagged extrinsically with 59Fe and measured by whole-body counting. We studied the effect on iron absorption of adding meat, ascorbic acid, soybean, tea, or bran to the test meal. A significant but modest effect of bran on iron absorption was observed in normal rats and of ascorbic acid and tea in ascorbate-depleted animals. However, the overall sensitivity of rats to dietary facilitators or inhibitors of nonheme iron absorption was not altered dramatically by ascorbic acid depletion. The relative insensitivity of rats to dietary factors affecting nonheme iron absorption in humans is not explained by differences in ascorbic acid metabolism between rats and humans.