Instead of increasing the risk for the digestive disorder diverticulitis , as has long been suspected, these foods may actually lower risk of the condition, according to findings from the first large study to address the issue.
The study was published Tuesday in TheJournal of the American Medical Association.
About a third of Americans will develop small pouches of the colon, a condition known as diverticulosis , by the time they reach age 60; two-thirds have the pouches by age 85.
Most people with diverticulosis experience no symptoms, but as many as one in four will develop diverticulitis, a potentially serious condition characterized by intense pain in the lower, left side of the abdomen and possible nausea , vomiting, cramping, and bleeding, according to the National Institutes of Health.
Since at least the 1950s many doctors have advised patients who have diverticular disease to restrict nuts, corn, popcorn -- and even vegetables with seeds like tomatoes -- on the theory that the indigestible components of these foods would lodge in the pouches, causing symptoms.
"It is not exactly clear where this idea came from because there are no studies showing this to be the case," researcher Lisa L. Strate, MD, MPH, tells WebMD. "It just became a part of medical lore."
Using data from an ongoing Harvard School of Public Health study of male health professionals, Strate and colleagues were able to examine the association between eating nuts, corn, and popcorn and diverticular disease.
Their analysis included 47,228 study participants who were between the ages of 40 and 75 at enrollment and had no history of diverticulosis, diverticulitis, or related diverticular complication.
All the men completed detailed questionnaires every few years designed to examine the foods they ate and their health status.
Nuts, Seeds, and Diverticulitis
During 18 years of follow-up, there were 801 cases of diverticulitis diagnosed and 383 cases of diverticular bleeding.
Men who ate nuts, corn, or popcorn frequently were found to have no greater risk for developing diverticulitis or diverticular bleeding than men who rarely ate the foods.
In fact, men who ate nuts at least twice a week had a 20% lower risk of diverticulitis than men who ate nuts less than once a month; men who ate popcorn at least twice a week had a 28% lower risk.
No association was seen between diverticulitis and eating corn, and no association with diverticular bleeding was seen with any of the foods. Also, no association was seen between the foods and development of uncomplicated diverticulosis.
"For decades people have been told that eating these foods increases complications associated with diverticular disease, but our results suggest they don't," Strate says.
Dallas-based gastrointerologist Lawrence R. Schiller, MD, tells WebMD that he no longer recommends that his patients with diverticular disease restrict any foods, including nuts, corn, and popcorn. But he adds that many patients still avoid these foods.
Schiller is program director of the gastrointerology fellowship program at the Baylor University Medical Center in Dallas.
Many doctors recommend that patients with diverticular disease eat a high-fiber diet ; nuts, corn and popcorn are high-fiber foods.
"The idea that these foods should be avoided is so deeply ingrained in people that I really don't think this study will represent the nail in the coffin," he says. "But it is very well done and a useful contribution to the literature. Now when patients ask me about this I can tell them that there is not only no evidence of harm from eating these foods, there is evidence suggesting a benefit."
By Salynn Boyles
Reviewed by Louise Chang
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