Ask the Doctors: Initial studies link added sugar, inflammatory bowel disease

Dear Doctor: I am 32 and just learned I have IBD. My doctor thinks the fact that, in my family, we eat a lot of sweets has something to do with it. It is genetic. Do you think it could be from too much sugar?

A. Inflammatory bowel disease, or IBD, is a term used to describe a group of disorders that arise from chronic inflammation of the digestive tract.

The most common of these are Crohn’s disease and ulcerative colitis. Though Crohn’s disease can affect any part of the digestive tract, most people experience problems in the area between the ileum, which is the end of the small intestine, and the start of the colon, or large intestine.

In ulcerative colitis, a person develops sores along the inner lining of the colon and rectum.

Ulcerative colitis and Crohn’s disease can cause abdominal pain, diarrhea, rectal bleeding, urgency to defecate, unintended weight loss and fatigue.

It’s true there’s evidence that IBD, which affects upwards of 3 million people in the United States, runs in families. Stress, diet and age also appear to play a role. Ulcerative colitis and Crohn’s disease often develop in the 20s and 30s. IBDs also are believed to arise from immune system impairment.

This brings us to your doctor linking your diagnosis to excessive sugar consumption. A study involving mice, not humans, that was published last fall in the journal Science Translational Medicine found evidence that added sugar in the diet can lead to IBD and make existing disease worse. Americans eat an estimated 65 to 70 pounds of added sugar per year, the highest rate in the world. Considering that the U.S. accounts for from one-third to one-half of all cases of IBD worldwide, it’s easy to see how the IBD-sugar connection became a subject of inquiry.

In that study, researchers looked at three groups of mice — those with a healthy gut, a group genetically predisposed to develop colitis and a group fed a compound to induce colitis. The mice were then further divided. Some received simple sugars for seven days in concentrations equivalent to a soft drink. Others had no added sugars. At the end of the week, the mice on the sugary diets developed colitis far more severe than the sugar-free mice. The gut microbiomes of all the sugar-fed mice were significantly altered, with a marked increase in bacteria that degrade the protective mucus that lines the gut.

Whether eating sugar erodes the protective mucus in the guts of humans remains unproven. But these findings are intriguing. We think cutting back would be good for your gut and your general health.

Dr. Eve Glazier is an internist and associate professor of medicine at UCLA Health. Dr. Elizabeth Ko is an internist and assistant professor of medicine at UCLA Health.