Fructose is a sugar found naturally in fruits, honey and some syrups. Fructose is also a basic component in table sugar (sucrose), and it's used to sweeten many processed foods and beverages. In addition, sorbitol — a sugar alcohol — interferes with fructose during normal digestion and should be avoided. So if you have fructose intolerance, you should avoid foods that contain fructose and sucrose as well as sorbitol. The phrase "fructose intolerance" is a general term that describes two possible conditions:
Hereditary fructose intolerance: People with hereditary fructose intolerance, a rare genetic disorder, lack an enzyme that breaks down fructose. This serious disorder, which is usually diagnosed at a young age, can lead to liver and kidney damage.
Fructose malabsorption: People with fructose malabsorption have difficulty digesting fructose. This is a less serious disorder because it doesn't result in liver or kidney damage. But it can cause abdominal pain, gas, bloating and diarrhea.
Fructose malabsorption is found in up to 30% of the population.
This condition is common in patients identified to be suffering symptoms of Irritable Bowel Syndrome (IBS), although occurrence in these patients is not higher than occurrence in the normal population. Conversely, patients with fructose malabsorption often fit the profile of those with IBS. A small proportion of patients with both fructose malabsorption and lactose intolerance also suffer from celiac disease.
Fructose is absorbed in the small intestine without help of digestive enzymes. Even in healthy persons, however, only about 25-50g of fructose per sitting can be properly absorbed. Persons with fructose malabsorption may absorb less than 25g per sitting. In the large intestine, fructose that hasn't been adequately absorbed osmotically reduces the absorption of water and is metabolized by normal colonic bacteria to short chain fatty acids and the gases hydrogen, carbon dioxide and methane. This abnormal increase in hydrogen is detectable with the hydrogen breath test.
The physiological consequences of fructose malabsorption include increasing osmotic load, providing substrate for rapid bacterial fermentation, changing gastrointestinal motility and altering the profile of normal bacteria in the gut. These effects are additive with other short-chain poorly absorbed carbohydrates such as sorbitol.
- Bloating (from fermentation in the small and large intestine)
- Diarrhea and/or constipation
- Stomach pain (as a result of muscle spasms, the intensity of which can vary from mild and chronic to acute but erratic)
- Vomiting (if great quantities are consumed)
- Early signs of mental depression
Restricting dietary intake of free fructose and/or fructans may provide symptom relief in a high proportion of patients with functional gut disorders.
Low Fructose/Fructan Diet
Foods that should be avoided by people with fructose malabsorption include:
- Foods and beverages containing greater >3g of fructose per serving
Foods with high fructose-to-glucose ratio:
Foods rich in fructans including:
- Wheat-containing products
- Foods containing sorbitol, present in some diet drinks and foods and other polyols (sugar alcohols), such as erythritol, mannitol, and other ingredients that end with -tol, commonly added as artificial sweeteners in commercial foods.
A low fructose diet can be difficult to understand, therefore at Gastroenterology Consultants we offer consultation and education from an in-house Registered Dietician.