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Dietary Fiber May Not Protect Against Diverticulosis After All

High Fiber and Diverticulosis

The standard diet therapy prescribed for a patient diagnosed with diverticulosis is typically a high-fiber diet which has been shown in some studies to reduce symptoms and the likelihood of developing an inflammatory state known as diverticulitis. However, researchers with the University of North Carolina at Chapel Hill School of Medicine have found the consuming a diet high in fibrous foods does not benefit patients and may actually increase risk.

Within the large intestine, people can develop a weak spot in the lining that bulges into a pouch, most commonly in the lower portion known as the sigmoid colon. Each pouch is known as a diverticulum; multiple pouches are called diverticula. The condition of having diverticula is called diverticulosis. About 10% of Americans older than 40 have diverticulosis and the risk increases with age.

Most people with diverticulosis do not have any discomfort or symptoms, however some may experience crampy pain in the lower abdomen, bloating or constipation. But when the diverticula become inflamed, pain can become severe. Diverticulitis can also lead to infection, bleeding, small tears (perforations) or blockage of the colon.

Observationally, the dominant theory about what causes diverticular disease has been the adoption of a low-fiber diet. It was noted in the early 1900s in the United States that when processed foods were introduced, the American diet became lacking in fiber and the incidence of diverticulosis and diverticulitis increased. Increasing the amount of fiber in the diet is promoted as a way to soften the stool and lower the pressure inside the colon so that bowel contents can move through more easily.

But unfortunately, this commonly-held belief has never been rigorously studied, notes Anne Peery MD, a fellow in the gastroenterology and hepatology division of UNC. Dr. Peery conducted a study of more than 2,000 people, aged 30 to 80 years, who had undergone outpatient colonoscopy at UNC Hospitals between 1998 and 2010. Participants were interviewed about diet, bowel movements, and level of physical activity.

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“We were surprised to find that a low-fiber diet was not associated with a higher prevalence of asymptomatic diverticulosis,” said Dr. Peery. In fact, those with the lowest fiber intake were 30 percent less likely to develop diverticula than those with the highest fiber intake. The study also found that constipation was not a risk factor and that having more frequent bowel movements also increased risk. Compared to those with fewer than seven bowel movements per week, individuals with more than 15 bowel movements per week were 70 percent more likely to develop diverticulosis.

But don’t change your diet yet. “While it is too early to tell patients what to do differently, these results are exciting for researchers,” said Peery. “Figuring out that we don’t know something gives us the opportunity to look at disease processes in new ways.”

Recommended foods for preventing diverticular disease include whole-grain breads and cereals, fruits such as apples and pears, vegetables including peas, spinach, and squash, and dried beans. Increasing fluid intake may also be beneficial.

The UNC study appears in the February 2012 issue of the Gastroenterology, a journal of the American Gastroenterological Association.

Source References:
UNC Health Care, Diets high in fiber won't protect against diverticulosis. Monday, January 23, 2012.
National Digestive Diseases Information Clearinghouse (NDDIC), National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), US Department of Health and Human Services; “Diverticulosis and Diverticulitis”

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