(P20-032-23) Dietary Fiber Utilization Depends on Fiber Physicochemical Properties and Gut Bacterial Dysbiosis

Objectives: The benefits of dietary fiber are associated with short-chain fatty acid (SCFA) production, improved gut barrier function and reduced inflammation. However, fibers differ in their health benefits with some showing adverse effects in an inflamed gut. The objective of this study is to assess the effect of fiber physicochemical properties such as rate of fermentability, solubility and structure complexity on fiber fermentation in the presence of healthy and colitis-associated bacteria.

Methods: Sixteen dietary fibers with low and high solubility and complexity and low, medium, and high fermentability were used in in vitro fermentation with healthy human gut bacteria. SCFAs were quantified using a GC-FID. Gas production (GP) was measured by syringe displacement. Resistant Maltodextrins (RMD), Pectin (HMP), Inulin (ChIn), and Wheat Bran (WB) were selected for a second in vitro fermentation using colitis-associated bacteria. 16S rRNA gene sequencing was performed using V3-V4 primers.

Results: Fiber fermentation with healthy human fecal sample showed that the fermentation rate was high for fibers such as Oat bran and Potato starch despite their low solubility. However, psyllium husk with a higher solubility showed a lower fermentation rate. HMP and ChIn resulted in a higher amount of SCFAs and GP, whereas, WB had lower levels of SCFAs and GP. In contrast, when using the UC fecal sample as inoculum, HMP and ChIn showed lower levels of SCFAs and GP, suggesting that the colitis-associated bacteria were not capable of fermenting the fibers or that fiber fermentation was delayed due to the low bacterial diversity. α-and β-diversity were significantly different between the UC and healthy donors. We suggest that the diversity dissimilarity between donors generated significant differences in SCFAs and GP levels when comparing them within each fiber.

Conclusions: Physicochemical properties and bacterial dysbiosis play a significant role in fiber assimilation, physiological behavior, and metabolite production in the gut.

Funding Sources: Whistler Center for Carbohydrate Research and Ralph W. and Grace M. Showalter Research Trust Award