Irritable bowel syndrome and fructose intolerance
Article Date: August 24, 2011
Partner Site: Gastroenterology Consultants
Irritable bowel syndrome
Irritable bowel syndrome (IBS) is characterized by unexplained abdominal pain, cramping, gas, bloating along with changes in bowel habits (constipation or diarrhea). IBS is a clinical diagnosis, diagnosed by a health care provider based on patient reported symptoms. There is no definitive diagnostic test for this disorder. IBS is the most common gastrointestinal disorder and is the second most common cause for missing work (after common cold). About 1 in 5 adults meet criteria for IBS but only about 15-20% seek medical help for this condition. Patients with IBS report an impaired quality of life and their bowel symptoms represent a major barrier to their general well being.
Patients with IBS are hypersensitive to gas or stool in the bowels and have been shown to have abnormal interactions between their brain and gut. IBS is not a single disease but a collection of disorders that cause symptoms consistent with the diagnosis of IBS. While there are several possible underlying reasons for IBS, there has been increasing interest in the role of dietary factors. Dietary intolerances may cause or exacerbate the symptoms of IBS. Examples of dietary intolerances include lactose (milk sugar), fructose (fruit sugar), fructan (fructose oligosaccharide), stachyose and raffinose (sugars in beans and other legumes).
Fructose (the fruit sugar) is a simple sugar (monosaccharide) present in fruits, vegetables and processed foods containing fruit or vegetable products. High fructose corn syrup contains large quantities of fructose. It is the most common sweetening agent used in a variety of processed foods. Americans consume between 10-50 grams of fructose in their diet every day. Dietary fructose is absorbed in the small intestine by receptors in the lining of the bowel. Humans have a limited ability to absorb fructose. Studies have shown that most healthy humans can tolerate 25 grams of fructose. Patients that are unable to absorb 25 grams of dietary fructose have dietary fructose intolerance (DFI)
Dietary fructose intolerance (DFI)
Dietary fructose intolerance is the inability to absorb a ‘normal’ dose of fructose in the small intestine. Fructose that is not absorbed in the small intestine is fermented by the bacteria in the large intestine (colon). When carbohydrates are fermented, gases (hydrogen, methane, carbon dioxide, hydrogen sulfide) and organic acids are made in the colon. These products of fermentation in turn cause a variety of symptoms in patients.
- Abdominal pain
The diagnosis of dietary fructose intolerance involves two steps. A detailed dietary history is needed to see if excessive amounts of dietary fructose are being consumed. Even healthy humans can have symptoms when large amounts of fructose (that overwhelms the body’s capacity to absorb fructose) are consumed.
The next step in the diagnosis is a breath test. During the test, patients consume a standard solution of fructose and provide a breath sample (blow into a bag) every 30 minutes for 3 hours. The gas samples are analyzed for intestinal gases. This can estimate the degree of fructose absorption. Patients record any symptoms experienced during the test. A physician evaluates the gas levels and symptoms to diagnose dietary fructose intolerance.
There are two potential treatment options for dietary fructose intolerance (a) dietary modification and (b) dietary supplements
(a) Dietary modification: The cornerstone of treatment of fructose intolerance is a fructose restricted diet. This diet can be stringent and hard to follow without expert help. Many processed foods contain fructose and require careful review of food labels to understand. It is impossible to completely eliminate fructose from our diets. However, changing the amount and the timing of fructose intake, under the guidance of physicians and dieticians can be very helpful in managing symptoms. Attempting a restricted diet without expert supervision can result in other dietary deficiencies which can lead to serious health problems.
Another dietary approach can be to balance fructose intake with simultaneous glucose intake. Studies have shown that glucose intake can increase fructose absorption. However, glucose intake can add to calorie intake and weight gain in some patients.
(b) Dietary supplements: There is emerging literature on certain natural dietary supplements that can enhance the absorption of fructose. These products are currently being researched and not yet available for routine use.
Fructose intolerance and IBS
Dietary fructose intolerance is seen in up to 30- 50% of patients with IBS. In some patients it may the main cause for their bowel symptoms, while in others it may contribute to their overall symptoms. Research studies have shown that treating fructose intolerance improves symptoms significantly in patients with irritable bowel syndrome. Also, there is emerging data that controlling the consumption of FODMAPs (fermentable oligo-di-monosaccharides and polyols) in the diet can help patients with IBS. FODMAPs are a family of sugars including fructose and fructan (chain of fructose molecules with glucose). Fructans are present in wheat, onions, asparagus and several other foods. Humans lack the enzymes to completely digest these foods and some patients with IBS cannot tolerate the byproducts of fermentation.
Irritable bowel syndrome is a common bowel disorder that limits quality of life. Many patients with IBS have dietary intolerances such as fructose and fructan intolerance. Careful evaluation for these disorders will allow for dietary changes and interventions that can improve symptoms and quality of life in patients with irritable bowel syndrome.
1. Food intolerance network. http://www.food-intolerance-network.com/index.php?option=com_content&view=category&layout=blog&id=2&Itemid=14
2. Rao SS, Attaluri A et al, Ability of the human small intestine to absorb fructose http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1994910/?tool=pubmed
3. Sheperd S, Gibson P, Fructose malabsorption and IBS, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1994910/?tool=pubmed
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