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BACKGROUND: Evidence suggests that increased distal short-chain fatty acid (SCFA) production beneficially impacts metabolic health. However, indigestible carbohydrate availability is limited in the distal colon; consequently, microbes shift toward protein fermentation, often linked to adverse metabolic health effects. We aimed to identify specific fiber (s) that promote saccharolytic fermentation in the distal colon and thereby may (partially) inhibit proteolytic fermentation. METHODS: Potato-fiber, pectin, and inulin were studied individually and in combination against a high (predigested) protein background using an in vitro model of the colon (TIM-2) inoculated with pooled, standardized fecal microbiota from individuals with overweight/obesity. Microbiota composition and activity were assessed at different timepoints to simulate the travel throughout the colon (proximal: 0-8 h, distal: 8-24 h) and compared to a high protein (HP) control, receiving only proteins. RESULTS: Fiber addition increased total SCFA production compared to HPcontrol (52. 11 ± 1. 49 vs 27. 07 ± 0. 26 mmol) whereas total branched-chain fatty acids (BCFA; a marker for protein fermentation) production only slightly decreased (3. 31 ± 0. 10 vs 4. 18 ± 0. 40 mmol). Combining potato-fiber and pectin led to the highest total and distal SCFA production and distal SCFA: BCFA. Fiber addition attenuated HP-induced increases in several bacterial taxa including Mogibacterium and Coprococcus, independent of fiber type. Additionally, time- and fiber-specific microbial signatures were identified: inulin increased Bifidobacterium (proximal) relative abundance and pectin and/or potato-fiber increased Prevotella 9 (distal) relative abundance. CONCLUSION: The most marked increase in distal colonic SCFA production was induced by combining potato-fiber and pectin. Further research should elucidate whether this switch toward saccharolytic fermentation translates into beneficial metabolic health effects in humans.
Deuren et al. (Sun,) studied this question.