July 14, 2003 -- A sugar that's naturally found in many fruits and is the main ingredient in a commonly used sweetener may be responsible for "unexplained" flatulence, bloating, pain, and other gastrointestinal symptoms in many people.
A new study, published in the June issue of the American Journal of Gastroenterology, suggests that fructose intolerance is a common yet underrecognized cause of digestive problems in some people. And the more fructose they consume, say researchers, the more likely they are to have problems.
An Abundant Sweetener
Fructose is a sugar abundant in honey and fruits such as apples, peaches, pears, and oranges. It's also the main ingredient in high-fructose corn syrup used in hundreds of juices, sodas, condiments, snacks, and other foods.
The problems occur because in many people fructose is not easily absorbed by the body. Fructose is usually absorbed in the small intestine, but for those with fructose intolerance, some travels to the colon, where bacteria ferment the fructose. This causes the release of hydrogen and methane gases, which cause pain, bloating, flatulence, and diarrhea.
Table sugar does not cause this reaction because it also contains glucose, which aids in the absorption process.
In their two-year study, researchers at the University of Iowa Carver College of Medicine studied 183 patients with unexplained digestive symptoms including flatulence, abdominal pain, belching, and altered bowel habits. None of the study participants were previously diagnosed with any digestive disorders.
Fructose Intolerance Test
Each participant completed questionnaires and took a test after drinking a solution containing the amount of fructose found in three glasses of apple juice, called a fructose breath test. The breath test measures the amount of hydrogen and methane gases produced in the intestines.
Researchers report that three in four patients experienced digestive symptoms after consuming the fructose solution. And among those testing positive on the fructose breath tests, nearly 90% had elevated levels of hydrogen while 11% had higher-than-average levels of methane.
These findings come as no surprise to two experts familiar with fructose intolerance.
"The fact that fructose is poorly tolerated has been known for long time," says Peter Beyer, RD, LD, of the University of Kansas Medical Center. "But what has happened in the last few decades is that fructose intake in the U.S. has increased as portion sizes have increased. As a result, likely so have these symptoms."
Last October, Beyer presented his own research at the annual meeting of the American College of Gastroenterology indicating that 60% of his study participants with no known digestive problems were found to be fructose intolerant at intake levels half of those used in this study's fructose solution. Beyer, who was not involved in the new research, suggests that doctors routinely give fructose breath tests in patients with unexplained digestive symptoms.
"I don't want to give the impression that people will double over in pain or have recurring diarrhea from drinking a glass of apple juice or having a soda," he tells WebMD. "But it can trigger symptoms in many people with no diagnosed [digestive] condition. And the more fructose they consume, the more problems they may have. These effects may be more severe and apparent in those with irritable bowel syndrome or other known [digestive] disorders."
Only 'Scattered Awareness'
Phil Jaffe, MD, spokesman for the American College of Gastroenterology and associate professor at the University of Connecticut School of Medicine, says that fructose intolerance has earned "scattered awareness" among his colleagues over the past decade but remains underdiagnosed.
"I don't think 75% of my patients who have bloating and discomfort are fructose intolerant, but it probably is a significant number," he tells WebMD. He routinely screens his patients for fructose intolerance.
"Not only was this study well done, but this is an important clinical issue because lots of people with bloating, gas, and other symptoms don't have a good handle on why they have these symptoms," says Jaffe, who also was not involved in the study.
"Unless you are specifically screened for fructose intolerance, you may not know it can be a cause of problems. And fructose is in virtually all processed foods because it is cheaper to use than cane sugar."
Both experts advise that if you notice digestive problems soon after eating, you should see your doctor about getting a fructose breath test. In addition to limiting high-fructose foods, spacing the amount consumed can help you side-step symptoms.
"The issue isn't that you are not able to absorb fructose entirely, it's that you are unable to absorb it in high amounts," says Jaffe. "So if you have a piece of fruit, wait a few hours before you have another if you are among those with these symptoms. If you have small amounts at a time, even if you have malaborption problems, it's likely that you'll better tolerate fructose. But life is too short to eliminate all those high-fructose foods from your diet."