Dietary inulin supplementation does not promote colonic iron absorption in a porcine model of anemia

Abstract

Anemic weaner pigs surgically fitted with cecal cannulas were fed a low iron corn-soy ration supplemented with or without 4% inulin (Raftilose Synergy, Orafti) for 5 weeks. On 7 consecutive days in week 4, pigs were administered 1mg 54Fe in the morning feed followed 6 hours later by a 0.5mg 58Fe cannula infusion to measure total and colonic iron absorption, respectively. Whole blood was drawn prior to the initial dosing and 14 days thereafter for hemoglobin measurement and stable isotope detection using mass spectrometry. After 5 weeks, pigs were euthanased to isolate lumen content from the jejunum, ileum, cecum, and proximal, mid and distal colon for microbial profiling using terminal restriction fragment length polymorphism (TRFLP). The prebiotic role of inulin was confirmed by increases in lactobacilli and bifidobacteria with concomitant reductions in clostridia and enterobacteria in all 4 large intestinal compartments of inulin-fed pigs compared to controls. Surprisingly, a similar prebiotic effect also occurred in the jejunum. Hemoglobin levels were similar between both diet groups. Total iron absorption was 25.8 ± 3.4 and 16.0 ± 2.4% in inulin supplemented and control pigs, respectively (P > 0.05), while colonic iron absorption was 0.4 ± 0.1 and 0.2 ± 0.1%, respectively (P > 0.05). These results suggest that the colon does not make a significant contribution to total iron absorption in anemic individuals.