Plantago seed

Psyllium seeds are comprised of dietary fibre which, when mixed with water forms a gel-like mass that works as a mild laxative. This gel-like mass subsequently moves down a patient's digestive system and makes stools softer by increasing their water contents. At the same time psyllium seed lubricates the intestine, which improves the transit of stools. Moreover, as the presence of the gel-like mass increases the stool bulk it also increases the tension and/or the stretch stimulus in the bowel wall which serves to trigger bowel movements.

The dietary fibre of which psyllium husk is comprised is fermented to various degrees by bacteria in the colon, resulting in production of carbon dioxide, hydrogen, methane, water, and short chain fatty acids, which are absorbed and brought into the hepatic circulation. In humans, such fibre reaches the large bowel in a highly polymerized form that is fermented to a limited extent, resulting in increased fecal concentration and excretion of short chain fatty acids.