Objective: To measure intestinal absorption and red blood cell incorporation of ferritin iron in healthy women with or without non-ferritin iron competitors
Design: 73 healthy women received 0.5 mg radiolabeled ferritin iron on 4 specific days over a 15 day period either by itself or with varying amounts (4.5 mg to 49.5 mg) of iron from ferrous sulphate, ferrous sulphate with ascorbic acid or hemoglobin. Some of the iron capsules were enteric coated and others not. Their iron status was measured prior to day 1 of the study and then again at day 14 and day 28 to determine the amount of radiolabeled ferritin iron that had been incorporated into red blood cells.
Rat intestinal segments were perfused with radiolabeled ferritin iron and compared with perfusion of a chelated form of ferric iron in order to compare absorption rate and mechanism.
Results: Nine times concentrations of ferrous sulphate and heme iron had no effect on the absorption of ferritin iron for the women. Enteric coated ferritin iron capsules had superior absorption to the non-enteric coated ferritin and ferrous sulphate capsules. Ferritin iron in the rat intestine was absorbed more slowly than with ferric iron.
Conclusions: Ferritin iron is absorbed by different pathways and mechanisms than both iron salts and heme iron. Inhibition of ferritin iron absorption only occurs when relatively large (greater than 10x) amounts of other iron sources are in competition in the digestive tract. The slower absorption rate and intact protein cage of the ferritin iron help protect the intestinal lining from free radical damage.