Psyllium, also referred to as Asian Psyllium (Plantago ovata), is a soluble fiber supplement that has been studied for its effects on various digestive disorders, including diverticulosis and diverticulitis. The primary rationale for its use in diverticular disease is its ability to increase stool bulk and soften stool, which may help reduce colonic pressure and the risk of further diverticula formation or symptomatic flare-ups. Several clinical guidelines and studies support the use of a high-fiber diet, including supplemental psyllium, for the management and prevention of diverticular disease complications. For example, a randomized trial published in Diseases of the Colon & Rectum (1995) found improvement in symptoms with fiber supplementation; however, the evidence for psyllium specifically in the acute phase of diverticulitis (inflammation and infection) is limited, and fiber is generally reintroduced after the acute episode resolves.

Major gastroenterology guidelines (such as those from the American Gastroenterological Association) recommend dietary fiber for patients with diverticular disease to reduce symptoms and prevent recurrence, often citing psyllium as a well-tolerated option. Nonetheless, while the bulk of evidence supports fiber for diverticular disease overall, direct high-quality evidence specifically for psyllium in diverticulitis (rather than diverticulosis or chronic symptoms) is less robust, hence the rating of 3. Psyllium is not recommended during acute diverticulitis with significant inflammation, but may be beneficial in chronic management or prevention.