New property of vitamin A and beta-carotene on human iron absorption: effect on phytate and polyphenols as inhibitors of iron absorption

One hundred and seventy four human subjects were studied to find out the in teraction of vitamin A or beta -carotene with the inhibitors of iron absorp tion, from a basal breakfast containing bread from either 100 g of precooke d corn flour or 100 g of white wheat flour, 50 g of cheese and 10 g of marg arine. Bread was labeled with either Fe-55 or Fe-59. This bread was made fr om commercially flours fortified with iron as ferrous fumarate and vitamins . It was noticed that the percentage of iron absorption from the breakfast prepared with precooked corn flour given alone and with different concentra tions of coffee was practically the same, while the iron absorption from th e breakfast prepared from wheat flour decreased from 6% when the breakfast was given alone, to less than 2% when it was given with different concentra tions of coffee. The only ingredient present in precooked corn flour and no t in wheat flour was vitamin A This difference encouraged the authors to pe rform further experiments using precooked corn and wheat flours fortified o nly with ferrous fumarate. These studies demonstrated that vitamin A inhibi ts the effect of the polyphenol and partially inhibits the effect phytate o n iron absorption. HPLC and spectrophotometric studies demonstrated an inte raction between vitamin A and iron. Other experiments, which included 100 v olunteers, were performed to test the effect of vitamin A and beta -caroten e on iron absorption from corn, wheat and rice. The presence of vitamin A i ncreased iron absorption up to 3 times for rice, 2.4 times for wheat and 1. 8 times for corn. beta -carotene increased absorption almost 3 times for th e three cereals tested, showing that both compounds were capable of prevent ing the inhibitory effect of phytates on iron absorption. This information suggest that vitamin A and beta -carotene form a complex with iron keeping it soluble in the intestinal lumen and preventing the inhibitory effect of phytates and polyphenols on iron absorption.