High-Fiber Diet No Help for Diverticulosis

A high-fiber diet affords no protection against asymptomatic diverticulosis; in fact, it may aggravate the condition, according to a new study.

Researchers at the University of North Carolina (UNC; Chapel Hill, USA) performed a cross-sectional study of 2,104 participants, 30-80 years old, who underwent outpatient colonoscopy between 1998 and 2010. Of these, 878 had diverticulosis, and the remaining 1,226 participants served as a control group. Diet and physical activity were assessed in interviews using validated instruments to determine whether low- or high-fat diets, diets that include large quantities of red meat, constipation, or physical inactivity increase risk for asymptomatic diverticulosis.

The results showed that the prevalence of diverticulosis increased with age, but high intake of fiber did not reduce it. Comparing all participants with diverticulosis, the researchers found that those three or more diverticula were significantly more likely to have the highest intake of dietary fiber, and the quartile with the highest fiber intake had a greater prevalence of diverticulosis than the lowest. Risk increased when calculated based on intake of total fiber, fiber from grains, soluble fiber, and insoluble fiber. Constipation, however, was not a risk factor; compared to individuals with less than seven bowel movements per week, individuals with over 15 bowel movements had a 70% greater risk for diverticulosis. The study was published in the January 27, 2012, issue of Gastroenterology.

“The most widely accepted hypothesis, which we dispute, is that a high-fiber diet bulks the stools, increases colon diameter, and decreases intraluminal pressures […],” concluded lead author Robert Sandler, MD, and colleagues of the department of medicine. “Our data demonstrated no association between fat, red meat, physical activity, and diverticulosis.”

Diverticulosis is the condition of having diverticula in the colon, which are pockets of the colonic mucosa and submucosa created through weakness of muscle layers in the colon wall. These are more common in the sigmoid colon, which is a common place for increased pressure. The condition is uncommon before the age of 40, and increases in incidence after that age. The most common complication is symptomatic colonic diverticulosis, when the motility of the bowel becomes disorganized, resulting in pain in the left lower abdomen and often is accompanied by the passage of small pellet-like stools and slime which relieves the pain.

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