Fructose malabsorption is the medical term for an inability to absorb fructose, or fruit sugar. The condition was formerly known as dietary fructose intolerance, and causes symptoms similar to lactose intolerance. Individuals with the disorder typically experience gastrointestinal discomfort when fructose is passed through the intestine instead of being absorbed by the body.
In most people, 25 to 50 grams (0.88 to 1.76 ounces) of fructose are absorbed by the small intestine in one sitting. Individuals with fructose malabsorption may absorb much less than this, which leads to fermentation and an increase in bacteria and yeast in the intestine. Common symptoms of fructose malabsorption include gas and bloating, abdominal discomfort, diarrhea or constipation, and nausea. In severe cases, hypoglycemia or fatty liver may result.
The condition is often misdiagnosed as lactose intolerance because the symptoms are so similar. A hydrogen breath test is usually employed for an accurate clinical diagnosis, and stool samples may also be taken. The breath test is a non-invasive procedure often used to diagnose patients with food intolerances.
During a hydrogen breath test for fructose malabsorption, the patient breathes into a tube and the doctor takes a base reading of the hydrogen in the breath. The patient is then required to consume a small amount of fructose and retake the test in 15 to 60 minute increments for as long as three hours. The doctor uses the readings from each test to decide if a patient is affected by the condition. In most cases, if the reading rises 20 parts per million (ppm) above the lowest reading, the patient will be diagnosed with fructose malabsorption. The excess hydrogen in the breath is caused by an overgrowth of intestinal bacteria, which is caused by the fructose that cannot be absorbed by the body.
Fructose malabsorption cannot be cured, but symptoms can be managed by dietary changes. Individuals diagnosed with the disorder should avoid foods that contain high amounts of fructose such as apples, pears, fruit juices, high fructose corn syrup, coconut, honey, watermelon and raisins. Soda, dried and canned fruits, sweet wine and products sweetened with sugar alcohols such as sorbitol or xylitol should also be avoided.
Although several fruits are off-limits to sufferers of the condition, there are many safe fructose malabsorption foods, including fruit such as peaches, plums, apricots, nectarines, blueberries, blackberries, strawberries, lemons, limes, bananas and pineapple. Each individual will be different, however, and some patients may not be able to tolerate the same foods as others. A food journal can be kept to monitor which foods cause symptoms and in what quantity. The foods that trigger discomfort can then be avoided.