Diagnosis of fructose malabsorption

What is the H2 fructose breath test?

The H2 fructose breath test is a medical diagnostic procedure to determine fructose malabsorption. This occurs when the small intestine cannot fully absorb fructose, causing it to enter the large intestine where it is fermented by bacteria. This often leads to symptoms such as bloating, abdominal pain and diarrhea.

What is the difference between fructose and fructan intolerance?

• Fructose malabsorption: Refers to the insufficient absorption of fructose in the small intestine. The excess fructose passes into the large intestine, where it causes discomfort.
• Fructan intolerance: Refers to fructans, a group of carbohydrates consisting of several fructose molecules. The body cannot digest fructans, which is why they are fermented by intestinal bacteria and cause symptoms similar to those of fructose malabsorption.

However, an H2 fructose breath test cannot directly differentiate between fructose and fructan intolerance. While fructose causes detectable hydrogen levels in the breath in the test, fructans are often diagnosed by an elimination diet.

Foods containing fructose

Foods with a high fructose content that can cause symptoms in the case of fructose malabsorption:

• Fruit: apples, pears, mangoes, watermelon, grapes
• Juices: apple juice, grape juice, pear juice
• Honey and agave syrup
• Soft drinks and sweetened lemonades with fructose-glucose syrup
• Sweets and processed foods with added fructose

Fructan-containing foods

Fructans are mainly found in certain vegetables and cereals:

• Vegetables: Onions, garlic, leeks, asparagus, artichokes
• Cereals: wheat, rye, barley
• Pulses: lentils, chickpeas
• Some processed foods with wheat or inulin as an ingredient

When is an H2 fructose breath test useful?

An H2 fructose breath test is recommended if the following symptoms occur after eating foods containing fructose:

• Flatulence
• Abdominal pain
• Diarrhea
• nausea
• Feeling of fullness

The test is particularly frequently carried out on patients with irritable bowel syndrome or chronic digestive complaints.

How does the H2 fructose breath test work?

The test measures the hydrogen content (H2) in the breath after ingesting a defined amount of fructose. The procedure is as follows:

1. Appear fasting
2. Basic breath sample: A first breath sample is taken.
3. Drink fructose: A standardized fructose solution is ingested.
4. Regular breath samples: breath samples are taken at regular intervals over 2-3 hours.
5. Evaluation: An increased H2 value in the breath indicates fructose malabsorption.

Preparation for the test

To ensure that the results are as reliable as possible, patients should observe the following:

• The day before: do not consume any flatulent foods (e.g. pulses, onions, cabbage) or carbonated drinks.
• 12 hours before the test: Do not eat anything, only drink water.
• No antibiotics or probiotics in the last two weeks: These can falsify the test result.

What do the test results mean?

• Positive test: An increased H2 concentration in the breath indicates fructose malabsorption. This means that the body is not absorbing enough fructose, which can lead to symptoms.
• Negative test: No increased H2 concentration means that fructose is absorbed normally.

Treatment and diet for fructose and fructan intolerance

If fructose malabsorption or fructan intolerance is diagnosed, the following measures can help:

• Low-fructose diet: avoid foods with a high fructose content such as apples, pears, honey or industrially sweetened products.
• Low-fructose diet: Reduce high-fructose foods such as wheat, onions, garlic and certain vegetables.
• Test individual tolerance: Small amounts of fructose or fructans are often tolerated, especially in combination with other food components.
• Nutritional advice: Professional advice helps to ensure a balanced diet despite restrictions.