Psyllium fiber is commonly recommended as part of the dietary management of diverticular disease, especially for preventing symptomatic flare-ups after an acute episode of diverticulitis has resolved. The rationale for its use is based on its ability to increase stool bulk and soften stool, thereby reducing colonic pressure and the risk of further diverticular complications. Several clinical guidelines, including those from the American Gastroenterological Association, suggest a high-fiber diet for patients with diverticulosis to reduce symptoms such as constipation and to potentially decrease the risk of recurrence of diverticulitis, although direct evidence for prevention of recurrent diverticulitis is limited.

Scientific studies demonstrate that psyllium (a soluble fiber) improves stool frequency and consistency, and some small trials have shown reductions in symptoms in patients with diverticular disease. However, high-quality, large randomized controlled trials specifically evaluating psyllium for diverticulitis prevention or treatment are lacking. Most recommendations are based on the established benefits of fiber for general colon health and extrapolated from observational studies showing lower prevalence of diverticular disease in populations with high-fiber diets.

In summary, while the direct evidence for psyllium in diverticulitis is moderate, its use is scientifically justified by its well-established effects on bowel habits and indirect evidence suggesting benefit for diverticular disease overall.