Is There a Link Between Fructose Intolerance and IBS?

Fructose is a type of sugar found in fruits, vegetables, and honey. Fructose is also found in high-fructose corn syrup, which is an artificial sweetener used in sodas, canned fruits, and packaged desserts. In some people, ingesting foods that contain this type of sugar causes unpleasant digestive symptoms, like bloating, abdominal discomfort, and diarrhea.

A fruit spread on a table
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Research suggests that this condition, called fructose intolerance, may contribute to or even cause the symptoms of intestinal distress seen in some patients with irritable bowel syndrome (IBS). In fact, the identification of fructose intolerance is a key component of the theory behind the use of a low-FODMAP diet for IBS.

Overview of Fructose Intolerance

Fructose intolerance occurs as a result of the sugar fructose not being fully absorbed in the small intestine. As a result, the undigested fructose makes its way into the large intestine where it is set upon and fermented by intestinal bacteria. This metabolism of fructose causes unwanted gas, bloating, diarrhea, and stomach pain.

Fructose intolerance is a markedly different condition than hereditary fructose intolerance, a genetic disorder typically diagnosed in infancy.

Research on the Connection to IBS

Research backs up the identification of fructose intolerance as a cause of intestinal distress, as well as its possible link to IBS.

One small study made a comparison between healthy individuals and people who were self-identified as suffering from fructose intolerance based on the fact that they experienced bloating and flatulence after eating certain fruits. The self-identified patients had higher breath hydrogen levels and did experience more bloating and flatulence as a result of drinking the fructose solution than did healthy individuals.

Another study that looked specifically at fructose intolerance in 80 adults diagnosed with IBS found that up to one-third of patients with suspected IBS had dietary fructose intolerance.

Interestingly, of these 80 patients, 26 participated in a follow-up assessment one year later. On follow-up, 14 of these patients reported that they were able to comply with a fructose-restricted diet, and these participants experienced significant improvement in the symptoms of pain, belching, bloating, indigestion and diarrhea. The patients who did not comply with the fructose-restricted diet continued to have symptoms.

Diagnosing Fructose Intolerance

Fructose intolerance is typically diagnosed by the hydrogen breath test, which measures the amount of hydrogen in the breath following the ingestion of a fructose solution.

Of note, the fructose intolerance breath test is similar to the lactose intolerance test, except that your breath is analyzed for hydrogen gas after consuming fructose dissolved in water (and not a lactose-containing beverage).

With the fructose intolerance breath test, a high level of hydrogen gas in your breath indicates that the fructose in the solution has been fermented by bacteria in the large intestine. This suggests that your small intestine is having difficulty absorbing the fructose.

Unfortunately, the hydrogen breath test is not completely reliable. It can show a positive result even if you don't have malabsorption. While some say the test is still valuable, others point out its unreliability.

Differential Diagnoses

In addition, small intestinal bacterial overgrowth (SIBO) is a possible diagnosis when the hydrogen breath test is positive. Your doctor must determine whether that SIBO or fructose intolerance is the proper diagnosis to describe your condition. The diagnosis of SIBO can be confirmed with a hydrogen breath test analyzed after drinking a sugar solution containing glucose or lactulose (not fructose).

A Word From Verywell

The idea that fructose intolerance may cause IBS in some people is still being teased out. That said, whether or not you have been diagnosed with IBS, if you are experiencing gastrointestinal symptoms after eating fructose-rich foods, it's reasonable to consider fructose intolerance as a possible explanation.

In addition to keeping a food diary, you may want to talk to your doctor about undergoing a hydrogen breath test. If diagnosed with fructose intolerance, an elimination diet or a low-FODMAP diet can be helpful.

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