A poorly fermented gel from psyllium seed husk increases excreta moisture and bile acid excretion in rats

Psyllium seed husk (PSH) increases stool output and lowers blood cholesterol levels in humans. PSH and three fractions isolated from it were meal-fed to colectomized rats and fermented in vitro to test the hypothesis that viscous, gel-forming fraction B was responsible for these physiological actions. Control rats were fed 50 g/kg cellulose. The concentration of each PSH fraction in the test meals was equivalent to its concentration in PSH. Yields of the fractions were: A, 171; B, 575; and C, 129 g/kg of PSH. The wet weight and moisture content of ileal excreta (IE) from rats fed test meals containing PSH or fraction B were greater than those measured in excreta from rats fed meals containing cellulose or the other two PSH fractions. Total bile acids in IE did not differ between rats fed PSH or fraction B and were greater in these groups than in the other groups. Fraction A was not fermented during 3 d of incubation; fraction B was poorly fermented, with approximately 30% of the constituent sugars disappearing; and fraction C was rapidly and nearly completely fermented. These results indicate that the gel-forming fraction we isolated from PSH is the physiologically active component of the husks.