Fructose is a monosaccharide, or a type of sugar formed by a single molecule, that is naturally present in varying amounts in all fruits. Fructose is also found as a dissacharide in table sugar, bound to glucose, and other sweeteners like high-fructose corn syrup, honey and agave syrup. However, some people have a condition called fructose intolerance or fructose malabsorption that prevents them from properly absorbing fructose, resulting in a lot of gastrointestinal symptoms. A new enzyme called xylose isomeras has been developed to help people with fructose malabsorption. Fructose intolerance or fructose malabsorption shouldn't be confused with dietary fructose intolerance, a very rare genetic disorder that requires a different dietary approach.
Fructose Malabsorption
In fructose malabsorption, your symptoms are not due to an enzyme defect, but rather to a problem with the transporters required to properly absorb fructose. The consequences of poorly absorbed fructose staying in your intestines include abdominal pain, bloating, flatulence, diarrhea or constipation. Fructose malabsorption can be diagnosed with a hydrogen breath test, similar to the test used to diagnose lactose intolerance. Once diagnosed with, or if you suspect, fructose malabsorption, you will need to avoid consuming large amounts of fructose, especially agave syrup, honey, high-fructose corn syrup and high-fructose fruits like apples, pears, cherries, fruit juices and dried fruits. In addition, large amounts of sugar, which comprises both glucose and fructose, in desserts, candies or other treats can also trigger your symptoms.
Enzyme
The problem with fructose intolerance or fructose malabsorption is the fructose transporter called GLUT5 is impaired, according to the August 2007 issue of "Practical Gastroenterology." However, the SCIOTEC Diagnostic Technologies laboratory in Austria developed an enzyme called xylose isomerase that is able to convert fructose to glucose, which can easily be absorbed by fructose malabsorbers. According to this lab, this enzyme, which is found in a pill, can be taken with your fructose-containing meals to prevent your usual uncomfortable gastrointestinal symptoms. This enzyme is not recommended for diabetics or people with hereditary fructose intolerance.
Dextrose
Another way to stimulate the absorption of fructose without enzymes is by adding dextrose to your meal. Dextrose is pure glucose and glucose can stimulate the absorption of fructose via a transporter called GLUT2. If you wish to consume an apple or other foods rich in fructose, adding some glucose can help facilitate the absorption of moderate amounts of fructose, although not everyone reacts the same way and you will need to assess the effectiveness of this strategy for yourself. The downside of using dextrose is that it adds extra sugar and calories to your diet, which is not a good option for diabetics or people trying to lose weight.
Fructans, Galactans, Lactose and Polyols
It is relatively common for people with fructose malabsorption to also have problems tolerating and properly absorbing other types of short-chain carbohydrates. For example, fructose malabsorbers often have trouble with fructans, a type of sugar found in onions and wheat; galactans, a sugar found in legumes; lactose, the sugar found in milk, yogurt and cheese; and polyols, a family of sugar found in many vegetables, fruits and sugar-free products. The enzyme xylose isomerase and added dextrose do not work for these other problematic sugars. Talk to a registered dietitian for help establishing a meal plan that is suitable for your food intolerances.
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