Fructose, the simple sugar found in honey, fruits and some soft drinks, may be to blame for unexplained stomach ailments like cramps, gas and diarrhea.

This sugar is the main sweetener used in Western diets, say a group of researchers at the University of Kansas Medical Center, but some people lack the ability to absorb fructose properly.

They believe the dietetic ingredient is responsible for a host of common gastrointestinal complaints, so they are urging doctors to use fructose breath tests as a diagnostic tool for unexplained abdominal maladies.

Their study suggests that fructose malabsorption affects a significant number of healthy adults.

Gastric woes arise when the fructose travels down the digestive tract into the colon, where some bacteria use the sugar as a food source and consequently flourish. In the process, hydrogen gas is released and may cause pain, bloating and diarrhea.

During their research, the investigators fed their subjects 25 grams of fructose -- the equivalent of a 12-ounce can of soda sweetened with high fructose corn syrup -- and then gathered breath samples.

Testing revealed an abnormal level of hydrogen gas in almost half of the participants. On another occasion, after the subjects had dined on 50 grams of fructose, about three-quarters of them exhaled high levels of hydrogen. If the sugar was digested normally, the gas would be absent from their breath.

"When given levels of fructose commonly consumed in the Western diet, a significant number of our subjects had both objective and subjective evidence of fructose malabsorption, meaning that the breath analysis showed hydrogen in excess of 20 parts per million, and they had symptoms like gas and diarrhea," says Peter Beyer of the University of Kansas Medical Center.

He believes physicians should add breath analysis for fructose intolerance to their diagnostic test reservoir.