Fructose malabsorption, also known as "dietary fructose intolerance," is a digestive disorder where the absorption of fructose is impaired by deficient fructose carriers in the cells of the small intestine. This results in an increased concentration of fructose in the entire intestine.
Carbohydrates are single sugars, or two sugars bound together, or thousands of sugars bound together called starch, or millions of sugars bound together called fiber. Fructose is a simple sugar. No carbohydrate can pass from your intestines into your bloodstream until it is broken down into a single sugar. For example, milk contains a double sugar called lactose that must be broken down into two single sugars before it can be absorbed into your bloodstream. Fifty percent of people on this earth get gas, cramping and diarrhea when they drink milk. To break the double sugar called lactose into the single sugars, your intestines must produce an enzyme called lactase. If your intestines do not produce lactase, you cannot split the double sugar into single sugars, and the double sugar cannot be absorbed in your upper intestines, so it passes to your colon, where bacteria ferment it to form gas, cramping and diarrhea.
Fructose is a single sugar that is absorbed much more slowly than another sugar called glucose. Most of the fructose in you intestines is converted to glucose and then absorbed into the bloodstream. The fructose that is absorbed goes directly to your liver where it is converted to glucose. Some people have intestines that do not convert fructose to glucose rapidly. Therefore, the fructose is not absorbed in the upper intestinal tract and it passes to the colon where bacteria ferment it to form gas, cramping and diarrhea.
This condition is found in about 30-40% of the population of Central Europe, and around half of these have symptoms resembling Irritable Bowel Syndrome.
This condition is common in patients identified to be suffering symptoms of Irritable Bowel Syndrome, although occurrence in these patients is not higher than occurrence in the normal population. Patients with fructose malabsorption often fit the profile of those with Irritable Bowel Syndrome.
Hereditary Fructose Intolerance (HFI) is a potentially fatal condition in which the liver enzymes that break up fructose are deficient. HFI is not the same as fructose malabsorption. HFI is usually diagnosed in young children and is considered very serious because it can cause damage to the liver and kidneys.