Diet and Diverticulitis

Do you remember The Whiners on Saturday Night Live? In the early 1980s, Joe Piscopo and Robin Duke played an annoying (and hilarious) couple who complained and whined about everything. They'd arrive at a restaurant, complain loudly about their diverticulitis (pronounced diverticulitiiiiiiiis) and how nothing on the menu would do. Funny stuff. But, as it turns out, it's not medically accurate.

The idea that dietary restrictions are critical for people with diverticular disease has been called into question.

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What Is Diverticulitis?

In diverticulosis, small pouches (diverticula) develop in the colon and bulge out. The cause is not known, though the condition is thought to be more common among people with low fiber diets. And its prevalence rises with age.

If the diverticula become inflamed, it's called diverticulitis. If they bleed, it's called diverticular hemorrhage. While antibiotics may calm down diverticulitis, surgery may be needed.

It seems logical that people with diverticular disease should avoid certain foods – especially "roughage" that travels through the digestive tract largely undigested. Corn, pumpkin seeds (or any other foods with seeds), nuts and popcorn husks, for example, might get trapped in a diverticulum and cause trouble.

Yet, the recommendations that people with diverticulitis avoid these foods were based on rather little evidence. So, researchers from University of Washington School of Medicine, Seattle, decided it was high time to put the question of diet and diverticulitis to the test. Their study was published in August 2008 in the Journal of the American Medical Association. Its results seem to discredit the common dietary advice people with diverticulitis have been getting for decades.

The study included more than 47,000 men ages 40 to 75 who kept track of their food intake over 18 years. None had diverticular disease at the start of the study. Here are the results.

While this study did not look at how food choices affected existing diverticular disease, its findings do call into question the impact of diet on this common condition.

People with diverticular disease are often advised not only to avoid popcorn, nuts and corn, but also to choose a high fiber diet. However, studies assessing the relationship between dietary fiber and diverticular disease come to mixed results. So, as with avoiding nuts and popcorn, dietary fiber may matter little for people with diverticular disease.

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Why the Myth?

I certainly thought that the advice to avoid nuts or popcorn if you have diverticulitis was undeniable and based on good evidence. But I was wrong.

In fact, medical myths persist in modern medicine because we often don't question the incorrect assumptions they're based on. Other factors that contribute to medical myth survival are:

• Inertia – When things have been a certain way for a long time, it may be a matter of "everybody knows that's true." The idea of studying it may seem unnecessary or even foolish. Or, more commonly, it doesn't occur to anyone to question "conventional wisdom."

• Research funding – If someone thinks to question a common recommendation and wants to study it, they'll have to get funding to pay for the research.

  Drug companies fund research because positive findings could lead to approval of the drug by the U.S. Food and Drug Administration — and huge profits.

  The government funds research that has potential to advance science or improve health (or both). It's not easy to get funding for studies that have no obvious profit-making potential or big public health payoff. (In fact, this recent study was funded by several government-based agencies, including the Agency for Healthcare Research and Quality, the National Heart, Lung, and Blood Institute, and the National Cancer Institute.)

• Harmlessness – Having to avoid certain foods if you have diverticular disease is certainly not dangerous or harmful in any way. So the pressing need to study its accuracy may be small.

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The Bottom Line

The distinction between medical myth and fact can be difficult to make. There are many examples of "truths" accepted by mainstream medicine that turn out to be myths. Take ulcers, for example. We used to think that they were caused by spicy foods or hot tempers.

Conversely, medical myths are just one convincing study away from being transformed into fact. If a well-designed study found that spicy foods did contribute to ulcer risk after all, we might have to move that myth back into the fact column.

The idea that corn, nuts and popcorn are bad for people with diverticular disease may be a myth that modern medicine has embraced for decades. But, we should never stop questioning even long-established beliefs. And we should always be ready to learn.

When the Whiners complained about their diverticulitis, they were not just being funny. They were also expressing concerns they might have learned from doctors at the time. Now, they'd just be funny.

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Lisa L. Strate, MD, MPH, et al. "Nut, corn, and popcorn cnsumption and the incidence of diverticular disease." 2008;300(8):907-914.

Robert H. Shmerling, M.D. is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.