pubs.acs.org/JAFC Published on Web 05/29/2009 © 2009 American Chemical Society 5250 J. Agric. Food Chem. 2009, 57, 5250–5256 DOI:10.1021/jf900698x Dietary Inulin Supplementation Does Not Promote Colonic Iron Absorption in a Porcine Model JANNINE K. PATTERSON, † MICHAEL A. RUTZKE, ‡ SUSAN L. FUBINI, § RAYMOND P. GLAHN, ‡ ROSS M. WELCH, ‡ XINGEN LEI, ) AND DENNIS D. MILLER* ,† † Department of Food Science and § College of Veterinary Medicine and ) Department of Animal Science, Cornell University, Ithaca, New York 14853, and ‡ Robert W. Holley Center for Agriculture and Health, United States Department of Agriculture/Agricultural Research Service (USDA/ARS), Ithaca, New York 14853 Prebiotics may enhance iron bioavailability by increasing iron absorption in the colon. Anemic pigs fitted with cecal cannulas were fed a low-iron diet with or without 4% inulin. Over 7 days, pigs were administered 1 mg of 54 Fe in the morning feed followed by cannula infusion of 0.5 mg of 58 Fe to measure total and colonic iron absorption, respectively. Whole blood was drawn prior to the initial dosing and 14 days thereafter for hemoglobin concentration and stable isotope ratio analyses. The prebiotic role of inulin was confirmed by increases in lactobacilli and bifidobacteria with reductions in clostridia using terminal restriction fragment length polymorphism (TRFLP). Total iron absorption was 23.2 ( 2.7 and 20.7 ( 3.5% (mean ( SEM; p > 0.05), while colonic iron absorption was 0.4 ( 0.1 and 1.0 ( 0.2% (mean ( SEM; p > 0.05) in inulin-fed and control pigs, respectively. These results show that the colon does not make a significant contribution to total iron absorption in iron- deficient pigs and that inulin does not affect iron absorption in the colon. KEYWORDS: Inulin; prebiotics; iron absorption; pig; stable isotopes INTRODUCTION Iron deficiency is currently the most prevalent nutritional deficiency worldwide (1, 2) and is associated with impaired physical work performance, poor immune function, impaired cognitive development, poor pregnancy outcomes, and possibly irreversible developmental delays in infants and toddlers (2-6). While many factors can contribute to iron deficiency, low bioavailability of dietary iron is widely considered to be a major cause (3, 7, 8). Currently, food fortification and distribution of iron supplements are the most effective strategies for combating iron deficiency (9, 10). However, compliance in taking iron supplements is often poor because of gastrointestinal upset. Also, low bioavailability from diets high in phytates and polyphenols may limit the effectiveness of fortification. Therefore, increasing the bioavailability of intrinsic dietary iron rather than fortifying food or giving iron supplements may represent a more viable alternative. Recent reports have suggested that prebiotics may enhance iron absorption (3, 11). Prebiotics, such as inulin, are nondigestible carbohydrates that, in humans, pass through the stomach and small intestine largely undigested and accumulate in the large intestine, where they promote a favorable enteric microbiota through the selective enhancement of beneficial bacterial populations, such as bifido- bacteria and lactobacilli, at the expense of pathogenic or oppor- tunistic populations, such as clostridia, enterobacteria, and proteolytic bacteroides species (12, 13). Prebiotics are currently being advocated as a therapeutic/preventative measure for many intestinal and extra intestinal diseases and disorders, including inflammatory bowel disease, diarrhea, and metabolic syndrome, and may also have applications in mineral nutrition (14-17). While several studies have demonstrated an enhancing effect of inulin and fructo-oligosaccharide prebiotics on calcium absorp- tion, their impact on iron absorption remains to be fully elucidated (18-21). Because the prebiotic effect is mediated through microbial fermentation in the large intestine, we hy- pothesized that inulin enhances iron bioavailability by increasing iron absorption in the large intestine. We therefore used a porcine model to determine the contribution of the small and large intestine to iron absorption from diets with or without supple- mental inulin. MATERIALS AND METHODS All experiments were performed according to National Rese- arch Council (NRC) guidelines and with prior approval of the Cornell University Institutional Animal Care and Use Committee (Protocol 2005-0089). Experimental Diets. Table 1 details the composition of the experi- mental diets. The basal diet was a corn-soy ration replete in all nutrients according to NRC recommendations for pigs (22 ), with the exception of iron, because no inorganic iron was added to the diet. The composition of the inulin diet was identical to that of the basal diet, with the following exception: inulin (Raftilose Synergy I, Orafti) was added at a dose of 40 g/kg diet at the expense of corn starch, which was present at this level in the basal diet. *To whom correspondence should be addressed: 119 Stocking Hall, Cornell University, Ithaca, NY 14853. Telephone: (607) 255-2895. Fax: (607) 254-4868. E-mail: ddm2@cornell.edu. Downloaded by US DEPT OF AGRI MASTER on July 16, 2009 Published on May 29, 2009 on http://pubs.acs.org | doi: 10.1021/jf900698x