Fructose is known as "fruit sugar". It is present in fruits, some vegetables, honey, granulated sugar, agave syrup and high-fructose corn syrup. In the past, the human diet was lower in fructose than it is today--think of how hard it was to get honey in the wild, for example, or what a treat it would have been in the past to have fruit out of season, much less a never-ending supply of ketchup, cookies, candy and other sweets. Now it seems as though fructose is everywhere in our food supply.
Our capacity to absorb fructose is easily overwhelmed; it is almost considered normal to experience abdominal pain, flatulence, bloating or diarrhea when we overdo the amount of fruit or fruit juice we consume--many people have experienced this phenomenon. But some of us experience symptoms with much smaller intakes of fructose. And most of us overlook the impact that large portions of sugary sweets, baked goods and soft drinks can have. And what about those honey or fruit juice concentrate-sweetened energy bars? Interestingly, apples are part of the traditional BRAT diet sometimes recommended to fight diarrhea. Umm...maybe apples and apple juice aren't such a good idea for some people with diarrhea.
Diagnostic dietary fructose intolerance tests are available, but are not ordered as frequently in the US as they are elsewhere. If you suspect you don't tolerate fructose very well, try cutting back on soft drink and other sweets. Limit tomato paste. Choose small portions of fruits that are lower in fructose, such as kiwi, berries, citrus fruits, and bananas. Read labels, and avoid or limit portion sizes of foods sweetened with honey, fructose, high-fructose corn syrup, agave syrup and fruit juice concentrates. See if you feel better!
Fructose malabsorption can occur on its own, or it can be part of the larger IBS picture.The FODMAPS elimination diet in IBS--Free at Last! can help you figure out how fructose fits into your IBS scenario.
It is important to distinguish dietary fructose intolerance, described in this posting, from hereditary fructose intolerance, which is a serious, hereditary disorder requiring a truly fructose-free diet.
Click here for more details about dietary fructose intolerance and how it causes GI symptoms.