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Psyllium Husk Alters the Intestinal Microbiota: A Randomized Trial

11/5/2019 12:51:04 PM
psylliumPsyllium is commonly used for constipation because it retains water in the small intestine, softening the stool and increasing stool frequency. Psyllium husk also contains oligosaccharides, such as arabinose and xylose, which have limited digestibility in humans but can be metabolized by intestinal microbiota. These oligosaccharides give psyllium prebiotic potential, with effects that may include increased growth of beneficial bacteria and increased production of short-chain fatty acids (SCFAs). Although these aspects of psyllium are known, less is understood about the precise effects of psyllium husk on the intestinal microbiota.

Trial examines psyllium effects on intestinal health

In 2 randomized, placebo-controlled trials, researchers explored the effects of psyllium husk supplementation on the intestinal microbiota of healthy subjects (study 1) and those with chronic idiopathic constipation (study 2). 
Eight healthy adults took 7 grams of psyllium per day (as 14 grams of Metamucil) or a placebo for 7 days in study 1. Sixteen constipated adults took 21 grams of psyllium per day or a placebo for 7 days in study 2. Researchers measured gastrointestinal transit, fecal water content, SCFA composition, and the stool microbiota composition.

Psyllium alters microbiota, transit time

The healthy subjects and constipated patients differed significantly at baseline in microbial composition (constipated patients had higher Desulfovibrio and Adlercreutzia but lower Sutterella and Lachnospira) and the amount of fecal SCFAs (constipated patients had 2.2 times the fecal acetate).
Psyllium supplementation produced substantial changes in transit time, fecal water content, and concentration of SCFAs in both groups. Psyllium had a significant but small effect on the microbial composition of healthy adults (increasing Veillonella and decreasing Subdoligranulum). The effects on the microbial composition were much greater in constipated patients (increasing Lachnospira, Faecalibacterium, Phascolarctobacterium, Veillonella, and Sutterella and decreasing Coriobacteria and Christensenella).
The authors of the study concluded that psyllium husks introduce small but significant changes in the intestinal microbiota of both healthy and constipated patients. Without acknowledging that constipated patients received 3 times as much psyllium per day, the authors also concluded that the effects of psyllium on microbial composition are more pronounced in constipated patients. 
Jalanka J, Major G, Murray K et al. The Effect of Psyllium Husk on Intestinal Microbiota in Constipated Patients and Healthy Controls. Int J Mol Sci. 2019; 20.