Psyllium seed is a type of dietary fiber that is derived from the plant Plantago ovata. Psyllium husk is the outer layer of the seed that contains the highest amount of dietary fiber. Psyllium has a number of beneficial properties, including being a good source of soluble fiber, which can help to regulate blood sugar levels and lower cholesterol levels. Psyllium is also effective at absorbing water and expanding in the stomach, which can help to relieve constipation.