Dietary fructose, fat linked to irritable bowel syndrome

October 14, 2003 in Gastrointestinal Health, Nutrition Topics in the News

Dietary fructose, fat linked to irritable bowel syndrome

Findings from two separate studies suggest that both fructose and fat in the diet may contribute to symptoms of irritable bowel syndrome (IBS).

IBS -- not to be confused with inflammatory bowel disease that includes ulcerative colitis and Crohn's disease -- affects up to 15 percent of Americans. Symptoms are varied and can include diarrhea, bloating and constipation. The cause is often not clear.

Researchers from the University of Iowa Hospitals and Clinics in Iowa City previously found that 30 to 58 percent of patients with IBS symptoms, particularly those with diarrhea, were fructose intolerant. In the group's latest study involving 80 patients with IBS, 30 were found to be fructose intolerant.

To see whether a fructose-restricted diet would help curb IBS symptoms, the team gave these 30 patients written and oral instructions about eliminating fructose from their diet. After one year, 26 were available for follow-up interviews regarding their compliance with the dietary recommendations, and their IBS symptoms.

For the 54% of patients who complied with the fructose-restricted diet, bowel symptoms such as abdominal pain, bloating, and diarrhea, declined significantly. In some cases, abdominal pain was completely gone. Those people who stopped the fructose-restricted diet did not see any improvement in IBS symptoms.

In the second study, scientists from the Mayo Clinic and Foundation in Rochester, Minnesota, attempted to tease out the dietary factors that may explain some of the symptoms of IBS or indigestion (dyspepsia). They identified 102 subjects with IBS or dyspepsia and 119 healthy "controls" to serve as a comparison group, and had them complete the Harvard Food Frequency Questionnaire (HFFQ). A subset of 53 cases and 58 controls kept a diet diary for one week.

Compared with controls, patients with IBS or dyspepsia consumed a higher proportion of fat in their diet, and a lower proportion of carbohydrates. According to the diet diaries, patients suffering from IBS or dyspepsia also ate less sugar than healthy controls.

There were no significant between-group differences in protein, fiber, iron, calcium, niacin, or vitamins B1, B2, B6, B12, C, D, or E. They say future studies are needed to determine whether fat intake causes gastrointestinal symptoms.

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