Psyllium, a soluble fiber derived from the husks of Plantago ovata seeds, is commonly used to manage various gastrointestinal conditions, including diverticulosis and diverticulitis. The rationale is based on its ability to increase stool bulk and soften stool consistency, which may help to reduce colonic pressure and prevent the formation of new diverticula or complications in those with diverticulosis. Clinical guidelines and reviews, such as those by the American Gastroenterological Association, suggest that a high-fiber diet—including supplemental fiber like psyllium—may reduce the risk of symptomatic diverticular disease and recurrence following mild diverticulitis. However, the quality of evidence is low to moderate, with most data derived from observational studies or extrapolated from broader research on dietary fiber. Randomized controlled trials specifically evaluating psyllium for acute diverticulitis are lacking, and fiber supplementation is generally not recommended during acute inflammation or severe flare-ups due to concerns about bowel obstruction or worsening symptoms.

Therefore, while psyllium is not typically used to treat acute diverticulitis, it is often recommended as part of long-term management to help prevent recurrence or progression of diverticular disease. The evidence for its effectiveness is modest, justifying a rating of 2 out of 5.