The role of vitamin A on the inhibitors of nonheme iron absorption: preliminary results

The interaction of vitamin A and inhibitors of iron absorption from a basal breakfast containing bread from either 100 g of precooked maize flour or 100 g of wheat flour + 50 g of cheese + 10 g margarine was studied. These breads were labeled with either 55Fe or 59Fe. This basal breakfast was given alone on the first day of the study, and a beverage containing coffee or tea at different concentrations was administered with this breakfast on the following days. In the first three experiments performed, the bread was made from commercially available flours, fortified with iron as ferrous fumarate and vitamins. It can be noticed that whereas the iron absorption from the breakfast containing wheat bread was significantly reduced when given with different concentrations of coffee beverages, the bioavailability of iron from the breakfast containing precooked maize bread remained the same in spite of being administered with increasing concentrations of coffee beverages. The only ingredient present in precooked maize bread and not in wheat bread was vitamin A. In the other experiments, iron and vitamin A were added to the non-fortified precooked maize flour in our laboratory. In presence of vitamin A, nonheme iron absorption from the basal breakfast containing either coffee or tea was not statistically different from the breakfast without coffee, meaning that vitamin A can overcome the inhibition of coffee and tea on iron absorption and also prevents the inhibitory effect of phytates. The high performance liquid chromatography and spectrophotometric studies seem to indicate that during the digestive process, iron and vitamin A form a new prouct or complex, that keeps iron soluble even at pH6. All these data suggest that vitamin A binds iron liberated during digestive process and acts as a quelating agent, keeping iron soluble in the intestinal lumen and preventing the inhibition of polyphenols and phytates on nonheme iron absorption.