While occasional tummy aches may be a normal part of childhood, chronic abdominal gas pain, bloating, diarrhea, or constipation that doesn’t respond to common remedies is not. Now, researchers are proposing a possible culprit behind up to half of these puzzling cases of chronic childhood stomach upset: dietary fructose intolerance, otherwise known as fructose malabsorption.
The study, which was presented at the American College of Gastroenterology’s 75th Annual Scientific meeting, involved 245 children aged 2 to 18 with “chronic, unexplained” gastrointestinal symptoms. After testing all of them for fructose intolerance using the standard breath test–where patients drink a fructose-rich beverage and have breath samples collected at periodic intervals for several hours– the researchers found that over half of the kids tested positive for dietary fructose intolerance.
While few people have even ever heard of “fructose intolerance,” as a dietitian who works in a gastroenterology practice, I’m not particularly surprised by these results. Experts estimate that up to 30% of caucasian adults are fructose intolerant (the prevalence appears lower for non-caucasians), and in many of our patients who have been diagnosed with Irritable Bowel Syndrome, we find that fructose can be a significant dietary trigger of symptoms.
What is fructose, exactly?
Fructose is a type of sugar naturally found in fruits and honey that happens to be digested differently than other types of sugars. It can be found in foods on its own, or as a natural component of regular table sugar (a.k.a sucrose, or cane sugar), in which fructose and glucose are linked together and then split apart in the intestines in order to be digested. In a diet consisting primarily of whole, unprocessed foods, fructose naturally occurs at very low doses that are easily managed by most people. However, as more processed foods enter the diet, larger doses of fructose tend to accompany them, often in the form of an artificial sweetener called High Fructose Corn Syrup. And it’s this increased dose that appears to be testing the physiological limits of a normal digestive system to process and absorb this sugar efficiently.
National data reveal that fructose consumption has increased from 37g per day in the late 1970s to 55g per day in 1998-2004. Among adolescents, however, fructose intake reached an average about 73g per day — that’s 33 percent higher–mostly from sweetened drinks, grain-based desserts, and fruits and fruit juices.
As the data above suggest, American diets in general–and kids’ diets in particular–are loaded with fructose. Fructose is found in sports drinks, sodas, apple juice (and some other fruit juices), jelly, certain fruits, ketchup, and all sorts of packaged snacks. What’s more, when fructose intolerance is a problem, several different kinds of sugars and fiber can cause digestive problems including:
- pure fructose, of course, is the main culprit. This can be found naturally in sweeteners like honey and agave nectar, and also in the forms of regular or “cystalline” fructose, and high fructose corn syrup, added to foods and beverages
- “sugar alcohols” like sorbitol and xylitol, which are often used in sugarless gums and candies or to sweeten ”diet”/low-sugar products
- a so-called ”prebiotic” fiber called “inulin,” which is added to everything from low-fat yogurts to fiber-enriched cereals and granola bars
- and even large quantities of regular old table sugar, which can deliver a large dose of fructose, since table sugar is made up of equal parts fructose and glucose
If your child experiences chronic digestive woes and your doctor has ruled out the common culprits, consider visiting a gastroenterologist to have them tested for fructose intolerance. While different clinicians recommend many different versions of a low-fructose diet, a dietitian experienced with this condition can help your child navigate their new eating landscape and determine what foods he or she tolerates, and in what amounts.