Food iron absorption in man. Applications of the two pool extrinsic tag method to measure heme and nonheme iron absorption from the whole diet

Abstract

A new radioisotope method was used to measure iron absorption from the whole diet. The method is based on the concept that food iron is absorbed from 2 pools, the heme iron pool and the nonheme iron pool, which can be especially labeled with 2 radioiron isotopes given as hemoglobin and as an iron salt The purpose of this study was to test the accuracy of this 2 pool extrinsic tag method. The meals served were composed as an average of 6 wk consumption of 32 young enlisted men. The mean and total heme and nonheme iron absorption in all the 32 young men was 1.01±0.11. This figure agrees well with the mean daily losses expected for this group of subjects (1.0 mg). The conclusion can therefore be made that there are no major systematic errors in this method to measure the total iron absorption from a mixed diet. In 1 series a comparison was made of the absorption of heme and nonheme iron from the meals. A significant correlation between the absorption of the 2 kinds of iron was found. However, a much greater fraction of the heme iron was absorbed (37%) than of the nonheme iron (5%). The absorption both from breakfast and lunch was found to give a good prediction of the total daily nonheme iron absorption in 2 series. 1 series was designed compare the effect of 2 levels of iron fortification. There was a significant increase in iron absorption when the level of iron fortification of the meals was increased.