Studies in Iron Transportation Andmetabolism . Iv . Observations on the Absorption of Iron Fromthe

Most of the problems of iron therapy which have troubled physicians during the past half century are fundamentally traceable to our ignorance of the mechanism by which iron is absorbed from the intestinal tract. Had that mechanism been understood, the discussions centering about the relative efficacy of inorganic and organic iron preparations would not have occurred, and hematologists would not now be troubled by the clinical observation that simple ferrous salts are apparently utilized more completely for hemoglobin formation than are the complex ferric salts, such as iron and ammonium citrate (5 to 11 inc.). Adequate experimental analysis of the factors involved in iron absorption has been delayed by the lack of a method sufficiently dependable to measure immediate absorption from the intestinal tract. Investigators have been forced to utilize indirect procedures which measure: (1) the difference, in a given period of study, between the amount of iron ingested and the amount excreted in the urine and feces (12, 13); (2) the amount of iron which "disappears " from an isolated segment of intestine (14); or (3) the total increase in circulating hemoglobin resulting from the therapeutic administration of iron in various forms. From the hemoglobin increase is then calculated the percentage of iron that has been utilized (15, 16, 17). The first of these three approaches is open to the objection that no account can be taken of