The U.S. Department of Agriculture recommends two cups of fresh, frozen, canned or dried whole fruits each day for most people following a 2,000-calorie diet. However, some people have difficulty breaking down fruit in their digestive tract or absorbing fructose into their bloodstream. Fructose is a type of sugar that is naturally found in fruit. Humans have a limited ability for absorbing fructose. A special protein called GLUT5 carries fructose into the small cells of the intestines, and another protein called GLUT2 takes fructose from the cells and into the bloodstream.
People with fructose malabsorption (formerly called dietary fructose intolerance) have a deficiency of GLUT5 in their intestinal cells. Bacteria in the intestinal tract break down the fructose that the body can’t absorb. The undigested fructose forms gas and often causes gastrointestinal discomfort. Symptoms may include bloating, gassy pain and diarrhea. Up to 50 percent of adults can’t absorb large amounts of fructose, and about 10 percent can’t absorb even moderate amounts of fructose.
In addition to fruit, a number of sweeteners are high in fructose. High-fructose corn syrup, honey, maple-flavored syrup, molasses, sorghum and invert sugar may also cause uncomfortable symptoms. One possible reason why fructose malabsorption rates in the U.S. are high is from the widespread consumption of beverages—such as soft drinks—sweetened by high-fructose corn syrup.
People who have fructose intolerance should limit their consumption of high-fructose foods, such as:
- fruit juices,
- peas, and
Fruits and vegetables that are lower in fructose may be easier to digest, especially when they are part of a full meal. Lower-fructose foods include:
- green beans, and
So, if you are trying to eat the recommended servings of fruit every day but have digestion issues, ask your doctor if you may have fructose malabsorption and try lower-fructose foods as an alternative.
Barb Goodman, PhD, FAPS, is a professor of physiology at the University of South Dakota.