Psyllium, a soluble fiber derived from the husks of Plantago ovata seeds, is commonly used to promote bowel regularity and improve digestive health. Its use in diverticulitis is supported primarily in the context of diverticular disease or diverticulosis (the presence of diverticula without inflammation), rather than during acute diverticulitis (inflammation or infection of diverticula). The rationale is that a high-fiber diet, including fiber supplements like psyllium, can increase stool bulk and decrease colonic pressure, which may help prevent the formation of new diverticula and reduce symptoms such as constipation.

Several guidelines and clinical reviews, including those from the American Gastroenterological Association, recommend a high-fiber diet for patients with diverticulosis to help prevent disease progression and recurrence of symptoms. Psyllium is often highlighted because it is well-tolerated and effective at increasing fiber intake. However, strong evidence specifically for psyllium in acute diverticulitis is lacking; in fact, during flare-ups, a low-fiber or clear liquid diet is often recommended until symptoms resolve.

Overall, psyllium’s use in diverticulosis is supported by moderate scientific evidence for symptom management and prevention, but its use during acute diverticulitis is not recommended. The evidence rating of 3 reflects moderate support, primarily for prevention and management in the absence of active inflammation, rather than as a treatment for acute diverticulitis.