Cruciferous Vegetable Feeding Altered Human Gut Bacterial Community Composition

Abstract

In the human gut, bacterial myrosinase hydrolyzes glucosinolates (GS), phytochemicals found in cruciferous vegetables (CRV), to bioactive isothiocyanates (ITC). Only some bacteria express myrosinase; thus, inter‐individual variation in gut microbial composition may influence ITC exposure. We hypothesized that CRV feeding would selectively alter growth of certain bacteria, thereby altering human gut bacterial community composition. We tested this hypothesis in a controlled feeding study. Fecal samples were collected from 17 participants at the end of two 14‐day feeding periods: basal diet (no vegetables) and a high‐CRV diet (basal diet + broccoli, cauliflower, cabbage and radish sprouts, 12 g/kg body weight/day). Fecal bacterial composition was analyzed by the terminal restriction fragment length polymorphism (tRFLP) method on the bacterial 16S rRNA gene. Blocked multi‐response permutation procedures analysis revealed significant community composition differences between the two diets (P=0.016 for Alu I digestion; P=0.023 for Hae III digestion) and indicator‐species analysis suggested that specific tRFLP fragments characterized each diet. A non‐metric multidimensional scaling ordination plot also showed that bacterial community response to CRV was individual‐specific. In conclusion, gut bacterial community composition was altered by CRV feeding.