Plantain seed husks expand and become mucilaginous when wet, especially those of "P. psyllium", which is used in common over-the-counter bulk laxative and fiber supplement products such as Metamucil. "P. psyllium" seed is useful for constipation, irritable bowel syndrome, dietary fiber supplementation, and diverticular disease. Plantain has been consumed as human food since prehistory. For example, archaeological recovery along California's Central Coast has demonstrated use of this species as a food since the Millingstone Horizon. In particular, tender young plantain leaves can be eaten raw, and older leaves can be cooked. The seeds can be cooked like rice.