Effects of Dietary Fiber Supplementation on the Gut Microbiota and the Bowel Function in Healthy Adults: A Randomized Controlled Trial

Dietary fiber modulates the gut microbiota and improves the bowel function. However, its broader systemic effects in healthy adults remain unclear. This randomized, dou-ble-blind, placebo-controlled trial evaluated the effects of 4-week dietary fiber supple-mentation on the gut microbiota composition, the bowel-related quality of life, and secondary outcomes including sleep and skin condition. A total of 105 healthy adults received either placebo foods (2.2 g/day total fiber, 1.2 g/day fermentable fiber) or fi-ber-enriched foods (8.2 g/day total fiber, including 6.4 g/day fermentable fiber). The gut microbiota was assessed using 16S rRNA sequencing, and outcomes included stool diary, JPAC-QOL, OSA-MA, skin questionnaires, and fecal organic acids.