Fructose Intolerance & Lactulose

Many people with irritable bowel syndrome, celiac disease or other functional gut disorders also have fructose malabsorption. Also called dietary fructose intolerance, it shouldn't be confused with hereditary fructose intolerance, a rare and serious genetic disorder that warrants the elimination of all sources of fructose. With fructose malabsorption, fructose need to be limited according to your individual tolerance to prevent symptoms of abdominal distension, abdominal pain, cramping, diarrhea, constipation and flatulence.

Lactulose Hydrogen Breath Test

Lactulose is a sugar that is not naturally present in the foods but that can be recommended by doctor as a laxative. Lactulose is not digested and is used to do the first test done to diagnosed fructose malabsorption. On the day of the test, you will be give a dose of lactulose, and your breath will be analyzed every 20 to 30 minutes during the 2 to 3 following hours. Lactulose is not digested in humans, and this test serves at determining whether you produce more of the gas hydrogen or the gas methane in your breath.

Testing for Fructose Malabsorption

On a separate day, you can be tested for fructose malabsorption by following the same protocol used with the baseline test done with lactulose but using fructose instead. Depending on the type of gas produced with the lactulose test, the lab will measure the levels of either hydrogen or methane in your breath. The same test can also be done with lactose and sorbitol to identify a malabsorption of these other types of short-chain fermentable carbohydrates.

Foods to Avoid

If you are diagnosed with fructose malabsorption, you will need to avoid foods that contain a high amount of fructose or that contain more fructose than glucose. Stay away from fruits such as apples, pears, mangoes, peaches and watermelon and sweeteners such as honey, high-fructose corn syrup and agave syrup. Read the ingredient list carefully to ensure the foods you choose do not contain these foods. Fructans, which are a molecule made of a chain of fructose, can also cause problems for fructose malabsorbers and are found in wheat, rye and vegetables that include onions, leeks and garlic.

Safe Foods

Foods with a equal amounts of glucose and fructose or containing more glucose than fructose are usually safe for people with fructose malabsorption, especially if consumed in small quantities. Stick to low-fructose fruits such as grapefruit, oranges, kiwifruit, strawberries, blueberries and bananas and use sweeteners such as maple syrup or any type of regular sugar. If fructans also are a problem for you, your best bet is to stick to wheat-free or gluten-free grain products and vegetables such as green beans, red bell pepper, zucchini, lettuce and celery.