Psyllium seed husk are indigestible and are a source of soluble dietary fiber which may be fermented into butyrate, which is a pharmacologically active short-chain fatty acid, by butyrate-producing bacteria. They are used to relieve constipation, irritable bowel syndrome, and diarrhea. They are also used as a regular dietary supplement to improve and maintain regular GI transit. The inert bulk of the husks helps provide a constant volume of solid material irrespective of other aspects of the diet or any disease condition of the gut. Some recent research has shown they may be effective in lowering cholesterol and controlling certain types of diabetes.