The Effect of Psyllium Husk on Intestinal Microbiota in Constipated Patients and Healthy Controls. The Effect of Psyllium Husk on Intestinal Microbiota

Psyllium is a widely used treatment for constipation. It traps water in the intestine increasing stool water, easing defaecation and altering the colonic environment. Given the key role of the microbiota we aimed to assess the impact of psyllium on fecal microbiota. We performed two randomised, placebo-controlled, double-blinded trials comparing 7 days of psyllium with a placebo (maltodextrin) in 8 healthy volunteers and 16 constipated patients respectively. We measured the patients’ GI transit, fecal water content, SCFA and the stool microbiota composition. While psyllium supplement had a small but significant effect on the microbial composition of healthy adults (increasing Veillonella and decreasing Subdoligranulum), in constipated subjects there were greater effects with increased Lachnospira, Faecalibacterium, Phascolarctobacterium, Veillonella and Sutterella when compared to baseline, whereas the levels of uncultured Coriobacteria and Christensenella were decreased. We found several taxa to be associated with altered GI transit, SCFAs and fecal water content in these patients. Significant increases in three genera known to produce butyrate, Lachnospira, Roseburia and Faecalibacterium, correlated with increased faecal water. In summary, psyllium supplementation increased stool water and this was associated with significant changes in microbiota, most marked in constipated patients