Daily fiber supplementation after bariatric surgery demonstrates tolerability and influence on the fecal gut microbiome.

INTRODUCTION: This study assessed the feasibility and tolerance of a 30-day resistant potato starch (RPS) supplement in patients who recently underwent bariatric surgery and its effect on microbial production of fecal short-chain fatty acids (SCFA). METHODS: This clinical trial (ClinicalTrials.gov, identifier: NCT05653648), conducted at Dartmouth Hitchcock Medical Center, provided 30-days of RPS supplement (titration: 24 g for 15 days; 48 g for 15 days) starting 90-days post-op and assessed gastrointestinal symptoms, dietary intake (24 h recall), fecal SCFAs, and fecal gut microbiome (n = 30). RESULTS: The RPS supplement was well tolerated by participants (77% achieving consumption goal), with modest, but significant increases in self-reported gas (p = 0.004) and abdominal rumbling (p = 0.047). It was associated with an increase in the Bifidobacterium genus (LDA score >4, p < 0.001) and specifically, an enrichment of B. faecale/adolescentis (p = 0.006), one of two known primary degraders of RPS. No changes were observed in the abundance of cross-feeders or in SCFA concentrations. Alpha diversity measures were significantly lower post-RPS, and there was no change in species richness. DISCUSSION: This study demonstrated that a RPS supplement is tolerable in post-op bariatric patients and that the gut microbiome is responsive to fiber interventions. RPS increased the abundance of SCFA-producing bacteria but did not alter fecal SCFAs, likely due to competition among cross-feeders.