Clinical evidence of how specific fibre types might contribute to physiological effects with putative therapeutic value within the colon
| Desired colonic effects | References | ||||
| Normalise stool form | Normalise colonic transit | Minimise rapid fluctuations in luminal volume | Promote gut health | ||
| ↓ FODMAPs | ↔ Stool bulk. ↔ Stool water content (↓ when diarrhoea with high FODMAP intake). | ↔ Transit time (↑ when diarrhoea with high FODMAP intake). | ↓ Fluctuations in luminal volume within proximal colon. | ↓ Total bacteria and Bifidobacterium abundance. | 32 96 |
| Oligosaccharides | ↑ Stool bulk (minor). | ↔ Transit time. | ↑ Fluctuations in luminal volume within proximal colon. | Promotes ‘healthy’ microbiota. | 51 69 |
| Partially hydrolysed guar gum | ↑ Stool bulk. ↑ Stool water content. | Unknown. | Unknown. | Promotes ‘healthy’ microbiota. | 97 98 |
| Psyllium | ↑ Stool bulk. Normalises stool consistency. | ↔ Transit time (normalises if rapid or prolonged). | Unknown. | ↓ Hydrogen sulphide production (in vitro) Mopping effects. | 25 61–63 |
| Resistant starch | ↑ Stool bulk (minor). | Unknown. | Unknown. | Unclear. | 99 100 |
| Sterculia | ↔ Stool bulk. ↔ Stool consistency. | ↔ Transit time. | Unknown. | ↓ Hydrogen sulphide production (in vitro) Mopping effects. | 25 101 |
| Wheat bran | ↑ Stool bulk. ↑ Stool water content. | ↓ Transit time (normalises if rapid or prolonged). | Unclear (comparative data only). | Unclear. | 54 55 59 60 |
| Wheat bran+resistant starch | ↑ Stool bulk. ↑ Stool water content. | ↓ Transit time (normalises if rapid or prolonged). | Unclear. | Delivery of SCFA to distal colon. | 42 65 |
FODMAP, fermentable oligosaccharides, disaccharides, monosaccharides and polyols; SCFA, short-chain fatty acid.