Inhibition of intestinal iron absorption by laundry starch

The pathogenesis of iron deficiency anemia associated with amylophagia is usually attributed to dietary iron lack. However, large quantities of starch may inhibit intestinal iron absorption. Accordingly, studies were carried out to determine the effect of laundry starch on the intestinal absorption of inorganic and hemoglobin iron. In vitro, laundry starch bound 19 to 80% of the available 59FeSO4 and 34 to 68% of the available 59Fe-hemoglobin. Binding of both forms of iron was pH-dependent, with maximal binding at pH 7.0. In vivo, laundry starch significantly inhibited mucosal uptake of 59FeSO4 from isolated duodenal loops. In nonanemic rats, administration of laundry starch (100 mg) 1 hr before a 100-mug dose of 59FeSO4 significantly decreased the absorption of 59FeSO4, as compared to saline or low iron chow controls (6.2 +/- 2.0 versus 14.9 +/- 2.1 and -1.8 +/- 1.7, respectively, P less than 0.001). In anemic rats the absorption of either a 100-mug dose of 59FeSO4 or a 500-mug dose of 59Fe-hemoglobin was also significantly decreased by prior administration of laundry starch. The data obtained indicated that laundry starch (1) binds appreciable quantities of inorganic and hemoglobin iron in vitro; (2) inhibits the mucosal uptake or inorganic iron by isolated intestinal loops; (3) inhibits the intestinal absorption of inorganic iron in normal nonanemic rats, and (4) blunts the compensatory increase in inorganic and organic iron absorption in anemic rats.