Basic nutritional investigation Effects of dietary lipid composition and inulin-type fructans on mineral bioavailability in growing rats Alexandre Rodrigues Lobo, M.Sc. a , Jorge Mancini Filho, Ph.D. a , Eliana Parisi Alvares, Ph.D. b , Maria Lucia Cocato, M.Sc. a , and Célia Colli, Ph.D. a, * a Department of Food and Experimental Nutrition, Faculty of Pharmaceutical Sciences, University of São Paulo, São Paulo, Brazil b Department of Cell and Developmental Biology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil Manuscript received March 17, 2008; accepted August 4, 2008. Abstract Objective: This study reports the effects of feeding with a combination of inulin-type fructans (ITF) and fish oil (FO) on mineral absorption and bioavailability as part of a semipurified diet offered to rats. Methods: Male Wistar rats (n = 24) were fed a 15% lipid diet (soybean oil [SO] or a 1:0.3 fish:soybean oil mixture [FSO]) and diets containing the same sources of lipids supplemented with 10% ITF (Raftilose Synergy 1) ad libitum for 15 d. Feces and urine were collected for mineral analyses during the last 5 d of the test period. Fatty acid composition was determined in liver and cecal mucosa homogenates. Liver and bone mineral analyses were performed by atomic absorption spectrophotometry. Bone biomechanical analyses were evaluated by a 3-point bending test. Results: Compared with the controls, ITF-fed rats had enlarged ceca and a significant decrease in cecal content pH (P  0.001). The apparent mineral absorption was improved in these rats, and this effect was enhanced by dietary combination with FO for all minerals except for magnesium. Addition of ITF to the diet resulted in higher bone mineral content (calcium and zinc) and bone strength, but increased bone mineral content was only statistically significant in FO-fed animals. A decrease in liver iron stores (P = 0.015) was observed in rats fed FO, considering that ITF consumption returned to levels comparable to the SO control group. Conclusion: These findings confirm the positive influence of ITF on mineral bioavailability, which was potentiated by addition of FO to the diet. © 2009 Published by Elsevier Inc. Keywords: Inulin-type fructans; Fish oil; Polyunsaturated fatty acids; Mineral absorption; Bioavailability Introduction Inulin-type fructans (ITF; fructo-oligosaccharides [FOSs] and inulin) have been studied as prebiotic non-digestible oli- gosaccharides because they modulate the composition and metabolic activity of the intestinal microbiota, favoring the growth of bifidogenic bacteria rather than other species con- sidered to be pathogenic to the host [1]. Bacterial fermentation of ITF in the large intestine has been implicated in increased intestinal absorption and bioavailability of calcium (Ca) and magnesium (Mg) in animal (rat, pig) [2– 8] and human [9 –11] studies. In humans, the effects on intestinal Ca absorption seem to occur under conditions of greater mineral demands, such as during adolescence and after menopause [9 –11]. In contrast, studies examining the effects of ITF on micromineral absorp- tion (mainly copper [Cu], iron [Fe], and zinc [Zn]) are rela- tively scarce and present contradictory results [2]. The fermentative process favors the production of short- chain fatty acids (FAs), which reduce the luminal pH and enhance mineral solubility [2,5,12]. These effects are ac- companied by modifications in the architecture of the intes- tinal mucosa, which affect the cellularity and number of crypts, mechanisms that could contribute to an increase in the absorptive surface for mineral uptake [2,3,5,12,13]. Fur- thermore, dietary ITF seems to affect intestinal mineral absorption in rats by altering intestinal tight junction per- meability and the gene expression of mineral transporters such as calbindin-D 9k (for Ca), DMT-1, ferroportin (for Fe), Alexandre Rodrigues Lobo was supported by a fellowship from Con- selho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). This study was also supported by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). A portion of this work was presented in abstract form (Ann Nutr Metab 2007;51:213). * Corresponding author. Tel.: +55-11-3091-3651; fax: +55-11-3815-4410. E-mail address: cecolli@usp.br (C. Colli). Nutrition 25 (2009) 216 –225 www.elsevier.com/locate/nut 0899-9007/09/$ – see front matter © 2009 Published by Elsevier Inc. doi:10.1016/j.nut.2008.08.002