Fructose is a sugar commonly found in fresh fruit, honey, sugar, vegetables or fructose syrup used as an additive in processed foods. Fructose is absorbed in the small intestine. Some people are unable to completely absorb fructose, a phenomenon known as fructose malabsorption.

Nowadays many people suffer from fructose malabsorption as a result of intestinal dysbiosis or a very high fructose intake. Fructose malabsorption is not to be confused with fructose intolerance which is an inherited condition affecting children and causing severe health problems, such as liver conditions, convulsions and even mental impairment.

Undigested fructose is carried to the colon where the gut bacteria “gobble” it up. They produce a lot of gas which causes bloating, cramps and flatulence. Diarrhea may also occur. All these symptoms are not indicative of this condition as they may also occur in other food intolerances, such as non-coeliac gluten sensitivity and coeliac diseases.

Besides, fructose malabsorption may display symptoms similar to lactose intolerance and may occur in combination with lactose intolerance or a coeliac disease or both. Fructose malabsorption, and similarly lactose intolerance, coeliac diseases or non-coeliac gluten sensitivity, occur in association with the so-called Irritable Bowel Syndrome.

 Foods with a high fructose content include:

• Fruits: apple, pear, mango, peach, watermelon
• Honey
• Sweeteners: fructose sweeteners (high fructose corn syrup, corn syrup solids), concentrated fruit juices
• Foods with high fructan content (a form of fructose present in vegetables): wheat, onion, garlic, leek

Fructose malabsorption symptoms

Symptoms may start to occur at any age, their severity depending on the fructose intake. Some people tolerate a higher amount of fructose. The most common symptoms are those mentioned above: bloating, gas, cramps and diarrhea.

If diarrhea lasts longer than normal and its cause is not early and correctly diagnosed, other specific nutritional deficiencies may occur. The most common are related to folic acid, zinc, iron, tryptophan, calcium and vitamin C. As a result, patients may also experience symptoms associated with such deficiencies:

• Gastro-oesophageal reflux
• Chronic fatigue
• Headaches
• Constipation
• “Brain fog”
• Depression
• Anxiety

How can it be correctly diagnosed?

The standard test used to correctly diagnose fructose malabsorption is a hydrogen breath test which measures expired hydrogen concentrations. Unfortunately, this test is not largely available in Romania and, as a result, fructose malabsorption and lactose intolerance remain largely undiagnosed and cause other nutritional deficiencies in the long run.

How can it be treated?

1. Fructose malabsorption can be treated by switching to a low-fructose diet. The consumption of foods with high fructose or fructan content is thus drastically limited. The specific diet is a diet low in FODMAPs (Fermentable Oligo-Di-Monosaccharides and Polyols);

2. Bowel regeneration and rehabilitation – depending on the triggering cause, this method uses antibiotics (if needed) and probiotics in order to help rebalance gut flora. The treatment requires medical supervision.

3. Xylose Isomerase, a new generation enzyme produced in Austria. It converts fructose into glucose and alleviates digestive discomfort. This enzyme must not be used by diabetics and patients suffering from inherited fructose intolerance.

Is this a lifelong diet?

A strict diet is recommended for four to six weeks. Then, foods containing fructose will be reintroduced into the diet (one at every four days) and symptoms will be monitored. As already mentioned above, individuals tolerate fructose to different degrees. Therefore, careful monitoring is required in order to determine how they respond to treatment. Based on the patient’s response, particular foods may be included in or removed from their diet on a medium or long term.

An article by Dr. Alina Cernea