Fructose intolerance: when the sugar in fruits causes stomach ache
When we talk about fructose intolerance, we’re usually talking about fructose malabsorption, also called intestinal fructose intolerance. Those with this condition can't absorb the fructose in their diet through the small intestine. Instead, it’s broken down in the large intestine by intestinal bacteria. This process forms gas.
Fructose intolerance can develop at any age
The condition can be triggered by gastrointestinal diseases or medications that damage the intestines. Fructose intolerance can occur at any time of life.
Congenital metabolic disorder (hereditary fructose intolerance)
This form of fructose intolerance is very rare and is usually discovered in infancy. Those with the condition are obliged to avoid fructose as much as possible for the rest of their lives. A genetic test or tissue sample from the liver or small intestine can provide clarity.
How fructose intolerance is diagnosed
Blow here, please. Food intolerances often end in stomach pain, which makes them difficult to distinguish. A diagnosis is therefore essential. The H2 breath test has proven to be a good way to diagnose fructose intolerance. With this test, the patient drinks – on an empty stomach – a test solution containing fructose. Over a period of 2-3 hours, the hydrogen and methane content in the breath is measured at regular intervals. If the bacteria in the large intestine become active, the hydrogen and methane content in the breath increases significantly.
What is fructose?
Fructose, like glucose, is a form of carbohydrate that occurs naturally in many foods, not just fruits. With fructose – unlike glucose – the body doesn't release insulin. Its satiety signals are then lacking. However, this doesn’t mean that fructose should be avoided overall. In its natural form in fruits and vegetables, fructose isn't a problem, because when combined with other types of sugar, fructose can be better absorbed. Therefore even people who suffer from fructose intolerance can enjoy certain types of fruit. However, fructose is also used as an additive. Often a label that says “contains fructose” is paradoxically supposed to be healthy. But it’s precisely these products that don’t fill us up and cause blood sugar spikes.
Fructose isn't harmless
For a long time, fructose was considered the ideal sugar substitute for diabetes. Fructose is also cheap, which is why it’s often used in industrial products. It often appears on the ingredients list of diet and light products with the labels "less sugar” or “with fruit sweetener”. As a result, even people unaffected by the condition consume more than the recommended 35g of sugar per day.
These foods contain fructose
Fructose is often hidden in processed foods. For this reason, it’s always a good idea to look at the ingredients list. But, as the name suggests, natural fructose is also contained in fruits and vegetables. In many cases, however, it’s not necessary to give up fruit and vegetables permanently, because those with the condition can often tolerate a certain amount of sugar. Eating some fruits and vegetables will prevent any nutrient deficiency. How much of which foods is tolerated has to be checked individually with the help of a doctor or nutritionist.
Fruit with a lot of fructose
- berries in larger quantities
- dried fruit
Other foods that contain a lot of fructose
- Vegetables: artichokes, beans, broccoli, cabbage, tomatoes, onion and larger quantities of courgettes
- (Natural) sweeteners: honey, maple syrup, table sugar, corn syrup
Which fruits are well tolerated?
Bananas and tangerines are the secret winners among fruits: because they contain more glucose than fructose, they improve absorption in the small intestine. Fruits and vegetables with the same or more glucose than fructose are generally better tolerated. Fat and protein have the same effect. For this reason, the best way to enjoy strawberries is with yoghurt instead of strawberries on their own.