Ja. Marlett et al., An unfermented gel component of psyllium seed husk promotes laxation as a lubricant in humans, AM J CLIN N, 72(3), 2000, pp. 784-789
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 fracti
on of psyllium escapes microbial fermentation and is responsible for the ch
aracteristics that enhance laxation.
Design: Fifteen healthy adults consumed controlled diets for two 7-d period
s, one of which included 8.8 g dietary fiber provided by 15 g/d of a psylli
um seed husk preparation. All stools were collected and evaluated and diet
was monitored throughout.
Results: Psyllium significantly increased the apparent viscosity of an aque
ous stool extract, stool moisture, and wet and dry stool weights. A very vi
scous fraction, not present in low-fiber stool and containing predominantly
2 sugars that are also found in abundance in psyllium husk, was isolated f
rom psyllium stool.
Conclusions: In contrast with other viscous fibers that are fermented compl
etely in the colon, a component of psyllium is not fermented. This gel prov
ided lubrication that facilitated propulsion of colon contents and produced
a stool that was bulkier and more moist than were stools resulting with us
e of comparable amounts of other bowel-regulating fiber sources.