Comparison of diets containing whole wheat versus refined wheat flour, matched for total insoluble fiber, on fecal microbiota composition in C57BL/6 mice

Our objective was to explore the impact of whole wheat flour, after controlling for the effects of insoluble fiber, on intestinal microbiota. Two AIN93G‐based diets were prepared containing 38% of energy from carbohydrate derived from either whole (WW) or refined (RF) wheat flour. Differences in insoluble fiber between the diets were matched through the addition of cellulose to the RF diet. Diets were fed to C57Bl/6 mice (12/diet) for eight weeks with feces collected at week four. The V2+V3 region of the bacterial 16S rRNA gene was amplified from fecal DNA (10 mice/diet) using tag‐encoded primers for pyrosequencing (Roche 454 GS FLX). Sequences were processed using PyroTagger to yield a sample average of 21,781 sequences and 339 operational taxonomic units (OTUs) at 97% identity. The RDP Classifier was used for taxonomic assignment for each OTU. Hierarchical cluster and principal component analysis based on the 50 most abundant OTUs segregated the samples by diet. The percent of all OTUs classified by phylum, class, order or family did not differ between diets. However, of the 50 most abundant OTUs, the relative abundance of 24 OTUs significantly differed (P<0.05) by diet. These results suggest that differences in the types of fiber and/or phenolic compounds between the two diets affect intestinal microbiota at the level of the genus/species. Funded by the General Mills Bell Institute of Health and Nutrition.