EVIDENCE-BASED ANSWER
A diet high in fiber (particularly fruit and vegetable fiber) and low in fat and red meat may help to decrease the risk of symptomatic diverticular disease (strength of recommendation [SOR]: C, case-control studies and a large prospective cohort study). For people with diverticular disease, a diet high in fiber might decrease the risk of complications (SOR: C, case series). No studies have evaluated the effect of nut and seed avoidance.
CLINICAL COMMENTARY
Recommend natural sources of fiber for diverticulosis
David M. Schneider, MD
Sutter Santa Rosa Family Medicine Residency Program
“Conventional wisdom” dictates that physicians recommend a high-fiber diet to prevent symptoms in patients who are found to have diverticuli on endoscopic or radiographic studies, or who are diagnosed clinically with diverticulitis. Although there is a relative paucity of data, the clinical evidence, as set forth in this review, supports this practice. Insoluble fiber, and cellulose in particular, appears to be especially helpful.1
I tend to recommend natural dietary fiber in the form of vegetables and whole grains (primarily insoluble fiber), as well as legumes (soluble fiber to help reduce cholesterol and blunt glucose absorption). No studies are available to endorse the advice to avoid seeds and nuts; a survey of colorectal surgeons showed that half believed eating these foods made no difference in the disease course.2
It is noteworthy that acute diverticulitis is treated with clear liquids and a low-fiber diet during the exacerbation. This therapy is based on experience and conventional wisdom, and while there is no convincing evidence to support it, I still adhere to this recommendation.
Evidence summary
Approximately 60% of people living in Westernized countries who are older than 60 years will develop diverticulosis of the colon. Colonic diverticuli are thought to develop from an increase in intraluminal pressure. This pressure can be caused by colonic motility abnormalities, but a low-fiber diet can also result in a smaller stool mass and a less distended colon, thereby increasing intraluminal pressure.3
Because of strong epidemiological evidence that people from cultures with high-fiber diets are far less likely to develop diverticulosis than are people who live in cultures of low-fiber diets, it has been assumed that a diet high in fiber can prevent diverticulosis.4 Many small, uncontrolled studies have also investigated the effect of high-fiber diets and supplements on symptoms of diverticulosis and prevention of diverticulitis episodes.
One large, prospective study of 47,888 male health professionals gathered baseline dietary information in 1986. In 1990 and 1992, follow-up questionnaires asked the subjects if they had been diagnosed with diverticular disease in the interim, and whether they had symptoms of diverticulitis. The study showed a strong inverse relationship between fruit and vegetable fiber intake and risk of symptomatic diverticular disease. It also demonstrated a direct relationship between fat intake, particularly red meat, and symptomatic diverticular disease. For men in the highest quintile of total fat intake and lowest quintile of total fiber intake, the relative risk (RR) of diverticular disease was 2.35 (95% confidence interval [CI], 1.38–3.98) compared with men in the highest quintile of total fiber intake and lowest quintile of total fat intake. Men in the highest group of red meat intake and lowest quintile of fiber intake had a RR of 3.22 (95% CI, 1.46–7.54) compared with men with the lowest red meat intake and highest dietary fiber intake. In this study, cereal fiber did not reduce the risk of symptomatic diverticular disease.1
Two small randomized crossover studies evaluated the benefit of dietary fiber supplementation on symptomatic diverticular disease, with conflicting results (TABLE).5,6 One study found that sterculia gum with an antispasmodic, a high roughage diet, and bran tablets all improved symptomatic diverticular disease, with bran tablets associated with the greatest improvement.5 Another study found no significant differences between psyllium, bran, and placebo in reducing symptomatic diverticular disease.6 However, the amount of total fiber supplementation for each treatment regimen was less than in other studies.