Fructose Intolerance: Symptoms, Diagnosis, Diet

Those who do not tolerate fructose well will find that it can be found in quite a few foods. Find out what triggers the discomfort and what helps.

Fructose intolerance – briefly explained

  • The common fructose intolerance is correctly fructose malabsorption. This means that the body can only take up (absorb) a limited amount at one time in the intestine.
  • The fructose intolerance typically leads to gas/bloating, abdominal pain and diarrhea if you have consumed too much of this sugar.
  • The doctor can determine the intolerance using a breath test.
  • Anyone who is sensitive to fructose must find the individual threshold from which they can consume fruit, juice and sweets without problems. A completely fructose-free diet is not recommended.
  • Hereditary fructose intolerance occurs very rarely, in which affected people can absorb fructose through the intestine, but cannot break it down, they are intolerant to fructose and have to avoid it completely. The disease is serious and mostly affects babies.

This post is primarily concerned with the common fructose malabsorption.

Intolerance, malabsorption, maldigestion, intolerance, allergy: what the terms mean

Food intolerance is a term used to express that, for example, you do not tolerate fructose well if you consume it.

If you are intolerant to food, the body cannot break down a certain substance properly because it lacks the necessary enzyme. The substance accumulates in the organism. Example: hereditary fructose intolerance.

The much more common fructose intolerance, in which people can only absorb limited amounts of fructose in the intestine at one time, is malabsorption. The fructose is metabolized normally.

Maldigestion means: food components cannot or only insufficiently be broken down and absorbed by the body. Here too, an enzyme deficiency, for example in the pancreas, often plays a role.

food allergy is an immune system reaction to certain ingredients in food.

What is fructose intolerance / malabsorption?

Fruit sugar, also known as fructose, is a simple sugar that is found in many foods and gives them their sweetness. Especially in: fruit, fruit juices, jams, honey, some syrups and in numerous finished products. Fructose is also found in table sugar (sucrose), bound to glucose, i.e. grape sugar. Even longer-chain sugar molecules sometimes consist of many fructose molecules, for example, inulin and oligofructose.

In the mucous membrane of the small intestine, there are small transport proteins that carry nutrients from the inside of the intestine into the blood. Some of them – in addition to grape sugar – also transport fructose into the body. The amount of fructose that can be transported by the transport proteins at one time is naturally limited. This means that everyone can only tolerate a certain amount of fructose. The amount at which the transport proteins reach their capacity limit and a person reacts with complaints varies greatly from person to person.

If the fructose in the small intestine is insufficiently channelled into the blood via the transporter, the fructose reaches the large intestine. The bacteria naturally resident there use them as energy suppliers and quickly break down the sugar. The resulting gases and fatty acids can trigger the typical symptoms. Some of the gases are absorbed into the blood and exhaled through the lungs. The so-called breath test can be used to measure the increase in the concentration of the gas in the breath and thus make a diagnosis.

It is estimated that up to 50 percent of the population will experience symptoms such as flatulence and diarrhea if they consume 25 grams or more of fructose at once. As studies suggest, people with irritable bowel syndrome are more likely to respond to fructose with symptoms than healthy ones.

Doctors and scientists disagree as to whether fructose intolerance is a disease or whether it is a normal process in the body that simply depends on the amount of fructose.

Hereditary fructose intolerance

Hereditary fructose intolerance occurs only very rarely and is a congenital metabolic disease. Here the body lacks a special enzyme – fructose-1-phosphate aldolase – which is why it cannot break down fructose. The sugar accumulates in the intestinal wall of the small intestine, in the kidneys and in the liver. If left untreated, this intolerance can lead to severe liver and kidney dysfunction.

The disease usually manifests itself in babies. If you consume fructose for the first time, you will react quickly after ingestion with symptoms such as vomiting, diarrhea and hypoglycaemia, which can be expressed by sweating, dizziness and cramps, among other things. The doctor can determine the intolerance through a special blood test.

Babies and toddlers who suffer from hereditary fructose intolerance must strictly forego fructose in the first years of life, as well as sorbitol and table sugar. This poses a major task for parents. As the child grows older, it may be possible, to add very small amounts of fructose as a test.

Which symptoms are typical?

Flatulence and diarrhea are the most common complaints. In addition, there are abdominal pain, bloating, belching and nausea. The symptoms are expressed differently in each person. This depends, among other things, on the amount of fructose consumed and how sensitive the intestine reacts to the sugar.

How can fructose intolerance be diagnosed?

The symptoms caused by fructose consumption are very unspecific and are similar to other conditions. For example, there may be an intolerance to lactose, irritable bowel syndrome or inflammatory bowel diseases. Sometimes diet is simply to blame e.g. onions, cabbage, legumes and an excess of whole-grain products have a flatulence effect.

Anyone who has the feeling that flatulence and diarrhea could be due to an intolerance to fructose should consult a gastroenterologist. First, this can rule out other potential causes. Second, the doctor can do a breath test.

To do this, you have to drink a certain amount of fructose solution – on an empty stomach – and then blow into a special device at certain intervals. It measures the hydrogen content in the air we breathe. Because: If bacteria break down the fruit sweetness in the large intestine, hydrogen is produced, among other things. The more fructose accumulates in the large intestine because it was only absorbed to a limited extent through the mucous membrane of the small intestine, the more hydrogen is formed and exhaled. If this exceeds a specified value and you feel your typical symptoms, then this speaks for a fructose intolerance.

However, there is also criticism of these tests. Many people with stomach problems react to a large amount of fructose because only a limited amount can be introduced into the body. However, this does not necessarily mean that they have fructose malabsorption. In addition, the result of the test depends on the concentration of the fructose solution used.

Another way is to keep a detailed food diary. Write down how many grams you eat/drink of everything and how it makes you feel. Over time you will see a pattern emerge and can simply remove those foods or try smaller amounts.

Important: A breath test with fructose should not be done in the case of hereditary fructose intolerance. This can lead to life-threatening hypoglycaemia.

Which foods contain a lot of fructose?

Foods that are high in fructose include:

  • Fruit: apples, pears, mangoes, grapes, all dried fruits, persimmons, cherries, canned fruit, fruit compote
  • Drinks: fruit juices, lemonades, ready-made iced tea, other soft drinks
  • Confectionery / sweeteners: honey, pear syrup, apple syrup, agave syrup, jam, jelly, ice cream, invert sugar, table sugar
  • Others: Muesli, muesli/energy bars, fruit yoghurt

What to do?

Those who do not tolerate fructose well should not do without fruit completely. Many health-promoting ingredients that the body needs can be found in fruits. In addition, the functionality of the transport proteins decreases if you avoid fructose too radically. This means that the already reduced intake of fructose via the intestine worsens even further. An exception is hereditary fructose intolerance, in which a complete waiver is necessary.

If you have fructose malabsorption, your doctor will advise you to change your diet. Most of the time, you will have to avoid fructose as much as possible for around two to four weeks. In a nutrition and symptoms diary, write down what you have eaten and what symptoms are occurring. These should decrease significantly due to the fructose left out.

The test phase then begins. You are slowly starting to eat foods that contain fructose again – initially those that contain little of them. For example apricot, raspberries, citrus fruits, kiwi. Over the next few weeks, try other foods that contain fructose. With the help of the food and symptoms diary, you can find out which foods you can tolerate well and which ones less well. Likewise, from what amount the intestine becomes restless.

If renouncing the fruit sweetness does not help, and you still have stomach problems, you should consult a doctor again. Other ingredients in food can also cause problems, for example, lactose (milk sugar), histamine, gluten and so-called FODMAPs. FODMAP means: Fermentable oligo-, di- and monosaccharides as well as polyols. E.g. sugar, which consists of chains of different lengths, and sugar alcohols. All of them are broken down by bacteria in the colon, which can cause gas, diarrhea, and other symptoms. FODMAPs include fructose and longer-chain fructose molecules such as fructans.  Keep in mind that there are many food allergies that can trigger gastrointestinal problems.

If you suffer from Fructose intolerance or any other food intolerance, changing your diet is paramount. Ideally, you support this process with holistic colon hydrotherapy sessions to remove any trace of the intolerant foods from the system. We will also support you on your journey and cheer you on – as we know that changing your diet can be a very difficult process.

Fructose Intolerance

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