SUMMARY
New property of vitamin A and B-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 interaction of vitamin A or b -carotene with the inhibitors of iron absorption, from a basal breakfast containing bread from either 100 g of precooked corn flour or 100 g of white wheat flour, 50 g of cheese and 10 g of margarine. Bread was labeled with either ⁵⁵Fe or ⁵⁹Fe. This bread was made from 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 concentrations of coffee was practically the same, while the iron absorption from the breakfast prepared from wheat flour decreased from 6% when the breakfast was given alone, to less than 2% when it was given with different concentrations of coffee. The only ingredient present in precooked com flour and not in wheat flour was vitamin A This difference encouraged the authors to perform further experiments using precooked com and wheat flours fortified only with ferrous fumarate. These studies demonstrated that vitamin A inhibits the effect of the polyphenol and partially inhibits the effect phytate on iron absorption. HPLC and spectrophotometric studies demonstrated an interaction between vitamin A and iron. Other experiments, which included 100 volunteers, were performed to test the effect of vitamin A and b -carotene on iron absorption from com, wheat and rice. The presence of vitamin A increased iron absorption up to 3 times for rice, 2.4 times for wheat and 1.8 times for como b - carotene increased absorption almost 3 times for the three cereals tested, showingthat both compounds were capable ofpreventingthe inhibitory effect of phytates on iron absorption. This information suggest that vitamin A and B-carotene form a complex with ¡ron keeping it soluble in the intestinallumen and preventingthe inhibitory effect of phytates and polyphenols on iron absorption.

Key words: Iron, vitamin A, b -carotene, humans, phytates, polyphenols.



Recibido: 17/08/1999
Aceptado: 17/01/2000

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