Resistant potato starches (type 4 RS) exhibit varying effects on laxation with and without phylum level changes in microbiota: A randomised trial in young adults

• High intakes of resistant potato starches had little effect on gastrointestinal symptoms.
• Resistant potato starches (type 4 RS) varied in their effects on gastrointestinal function, specifically bowel movement frequency.
• Resistant potato starches (type 4 RS) showed mixed effects on microbiota, from no significant effect to phylum shifts in microbiota.
• The results of this study suggest that certain chemically modified potato starches (type 4 RS) may be resistant to fermentation or alternatively lack resistance to digestion.

The effects of resistant potato starches on gastrointestinal (GI) function and microbiota in healthy individuals were investigated. In a 6-week, double-blind, cross-over study, subjects (N = 57; 21M; 36F) were randomised to consume 30 g fibre/d from one of three chemically modified potato starches (RS4-A, soluble, viscous; RS4-B, soluble, non-viscous; RS4-C, insoluble, non-viscous) and control in beverages for 2 weeks with a 1-week washout and daily reporting of stool frequency, Bristol Stool Form Scale (BSFS), GI symptoms and compliance. Faecal microbiota was analysed by qPCR and 16S rRNA sequencing. Stool frequency and BSFS increased only with RS4-B (P < 0.01). GI symptoms were minimal with slight increases in flatulence with all interventions (P < 0.001). There were no changes in Lactobacillus or Bifidobacteria spp. However, RS4-B decreased Firmicutes (P = 0.02) and the ratio of Firmicutes to Bacteroidetes (P = 0.01). Resistant potato starches vary in their effects on GI function, which may be related to shifts in intestinal microbiota.