Components of fiber impair iron absorption in the dog

We have demonstrated previously that semipurified components of fiber bind ferrous iron in vitro. The present studies examined the possibility that these same fibers would decrease absorption of iron by the canine small bowel. Healthy and anemic dogs were studied chronically. Two preparations were needed; soluble components of fiber were tested by continuous perfusion of a duodenojejunal segment of approximately 100 cm, insoluble components were tested in Thiry-Vella fistulae of jejunum (25 cm). The results confirm that, 1) anemic dogs absorb iron more efficiently than do healthy animals, and 2) that there is a slight, but significant, decrease in iron absorption during the 4 to 6 h of an acute experiment. To obviate problems of interpretation because of the latter point, all studies featured a control period, before and after, the test period. Lignin and psyllium mucilage were potent inhibitors of iron absorption, pectin less so, and cellulose was without effect in this system. The results in vivo correlate well with the binding of iron in vitro.