An unfermented gel component of psyllium seed husk promotes laxation as a lubricant in humans

Am J Clin Nutr. 2000 Sep;72(3):784-9. doi: 10.1093/ajcn/72.3.784.


Background: In addition to increasing stool weight, supplements of psyllium seed husk produce stools that are slick and gelatinous.

Objective: Our purpose was to test the hypothesis that a gel-forming fraction of psyllium escapes microbial fermentation and is responsible for the characteristics that enhance laxation.

Design: Fifteen healthy adults consumed controlled diets for two 7-d periods, one of which included 8.8 g dietary fiber provided by 15 g/d of a psyllium seed husk preparation. All stools were collected and evaluated and diet was monitored throughout.

Results: Psyllium significantly increased the apparent viscosity of an aqueous stool extract, stool moisture, and wet and dry stool weights. A very viscous fraction, not present in low-fiber stool and containing predominantly 2 sugars that are also found in abundance in psyllium husk, was isolated from psyllium stool.

Conclusions: In contrast with other viscous fibers that are fermented completely in the colon, a component of psyllium is not fermented. This gel provided lubrication that facilitated propulsion of colon contents and produced a stool that was bulkier and more moist than were stools resulting with use of comparable amounts of other bowel-regulating fiber sources.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Carbohydrates / analysis
  • Cathartics / pharmacology*
  • Dietary Fiber / pharmacology
  • Feces / chemistry
  • Female
  • Fermentation
  • Gels
  • Humans
  • Male
  • Psyllium / pharmacology*
  • Viscosity
  • Water / analysis


  • Carbohydrates
  • Cathartics
  • Dietary Fiber
  • Gels
  • Water
  • Psyllium