IRON-ABSORPTION FROM THE WHOLE DIET IN MEN - HOW EFFECTIVE IS THE REGULATION OF IRON-ABSORPTION

Iron absorption from the whole diet, which contained a highly bioavail able form of iron, was measured for 5 d in 31 healthy men, including 1 2 blood donors. Nonheme iron in all meals was labeled with an extrinsi c, inorganic radioiron tracer added in amounts to ensure uniform Speci fic activity in all meals. Heme iron was labeled similarly by using he moglobin biosynthetically labeled with another radioiron tracer. There was a good inverse relation between total absorption and concentratio n of serum ferritin up to approximate to 60 mu g/L. In subjects with s erum ferritin > 60 mu g/L there was no relation to iron absorption. At this serum ferritin concentration, absorption decreased to a level ju st sufficient to cover basal iron losses, implying that at a serum fer ritin concentration greater than or equal to 60 mu g/L no further accu mulation of iron stores will occur by dietary iron absorption. The fin dings thus suggest that in normal subjects there is no risk of develop ing iron overload by iron absorption from the diet even if the diet is fortified. Similar findings were made previously in two studies in wo men, both of which indicated an effective control of absorption. At th e same serum ferritin concentration the absorption per kilogram body w eight was the same in men and women served identical diets with a high iron bioavailability. These new observations strongly suggest that tr anslation of serum ferritin concentration into amounts of stored iron should be made with caution and that in subjects with high serum ferri tin concentrations, other causes than increased iron stores should be considered. There was effective control of both heme- and nonheme-iron absorption but their relations to iron status were different.