Dietary Fibers of Tree Nuts Differ in Composition and Distinctly Impact the Fecal Microbiota and Metabolic Outcomes .

This study aimed to evaluate and compare the effects of dietary fibers (DFs) of commercially important tree nuts (almond, cashew, hazelnut, pistachio, and walnut) on gut microbiota . Microbial compositions and short-chain fatty acids were determined using 16S rRNA sequencing and gas chromatography (GC), respectively. Neutral and acidic monosaccharides were analyzed using GC/MS and spectrophotometry, respectively. Our results revealed that cashew fibers exhibit higher butyrate formation compared to others. Accordingly, cashew fiber promoted butyric acid-producing bacteria-related operational taxonomic units (OTUs; and ) at higher relative abundances. The higher butyrogenic capacity of cashew fiber is mainly attributed to its higher soluble/total DF ratio and remarkably distinct monosaccharide composition. Additionally, nut fibers stimulated family - and -related OTUs. These findings show that although the degree of promotion is nut type-dependent, nut fibers are generally capable of promoting beneficial microbes in the colon, further suggesting that DFs of tree nuts are contributing factors to their health-promoting effects.