Letzte Aktualisierung am 11. December 2023 von Dr. Michael Zechmann-Khreis
Fructose intolerance: symptoms
In intestinal fructose intolerance, the GLUT-5 transporter probably does not function properly or too few such transporters are present. This means that the fructose cannot be absorbed via the small intestine. It remains in the intestine and is transported to the next section of the intestine, the large intestine. In the large intestine, various bacteria then metabolize the fructose into gases such as hydrogen (H2) ,CO2 and also into short-chain fatty acids. The hydrogen does not cause any symptoms, but is used for diagnosis with an H2 breath test. TheCO2 leads to flatulence and abdominal pain. The short-chain fatty acids create an osmotic gradient (i.e. an imbalance in the local water balance) and thus a penetration of fluid into the intestinal lumen, which leads to watery diarrhea as a symptom of fructose intolerance. Some types of bacteria are more likely to produce methane. This “paralyzes” the intestines, resulting in constipation , which is also a symptom of intestinal fructose intolerance.
The most common symptoms of fructose intolerance can therefore be
- Diarrhea / constipation
- Abdominal pain
Many other symptoms can also occur. These include:
- Reflux & heartburn | Facebook group on this topic
- Vomiting – rare
- Fatigue – frequent
- Depressive moods (NOT depression!) – frequent
- Headaches (including migraines) – frequent
- Dizziness – rare
The severity of the symptoms varies greatly and can vary from day to day. day vary. One day you can handle a few strawberries, the next The next day you get diarrhea. If you have fructose intolerance, the trick is to slowly adapt to the new to feel your body and learn to listen to your body.
You should do this in conjunction with a competent and state-certified nutritionist!
Time delay of the symptoms
Another problem is the time delay of the symptoms. Some patients report that symptoms do not appear until 24-48 hours after consuming fructose, with a maximum of 24 hours usually passing. The symptoms never occur immediately after consumption, as the fructose must first reach the intestine. This takes approx. 10-20 minutes.
Fructose intolerance. Treatment
If you forget about your diet or simply go overboard, you will be plagued by the usual symptoms of fructose intolerance. A few tricks can help here – depending on the individual. You can place hot-water bottles on your lower abdomen, drink yarrow, fennel, caraway or other decongestant teas. If you get heartburn, you can also counteract this with suitable medication or teas. Nausea can also be treated with appropriate medication. Please always discuss these measures with your doctor. He will work with you to find the right medication. Ginger tea is low in fructose and helps against nausea, for example.
Of course, it is important not to go overboard in the first place or to avoid the symptoms from the outset. If you get diarrhea, it is advisable to use soft toilet paper and to lubricate the anus with a skin cream or wound healing ointment after a bowel movement.
Basic treatment of intestinal fructose intolerance
You should take a break for 2-4 weeks after the diagnosis. Fructose is completely avoided here. After a test phase in which you approach your individual tolerance limit, the permanent diet begins. This permanent diet should be possible without major restrictions. It is important never to completely avoid sugar or sugar alcohols, as this only exacerbates the problem. You should always push your limits and test your tolerance again and again.
Intestinal cleansing – Fasting
Intestinal cleansing is a good way to make your own body “fit” again after the diagnosis and to rehabilitate any intestinal colonization. In any case, your doctor should decide whether this sanitation is gentle or needs to be “prepared” with antibiotics! Regular fasting or detoxification, i.e. an annual fructose fast of around 2 weeks, improves the well-being of most people affected.
The glucose trick helps with fructose intolerance
The absorption of fructose is significantly improved by the simultaneous absorption of glucose. As glucose facilitates the absorption of fructose in the small intestine (although it should be noted that this varies from person to person and depends on a number of variables – for example, the total fructose per day must be taken into account), the intake of glucose can improve the tolerance of fructose-containing foods.
The most important thing here is that glucose is absorbed very quickly. is absorbed, whereas fructose remains in the intestine for a relatively long time. The This means that if you consume 1g of fructose and 1g of glucose, you already have after a short time a fructose surplus is present, since the glucose was recorded more quickly. It is therefore advisable to consume more glucose than fructose intake.
Caution: This trick should only be used rarely – and after the grace period – as excessive consumption of glucose has negative effects on insulin levels and other nutritional factors.
Enzyme for ingestion
There is now also help for intestinal fructose intolerance: the enzyme xylose isomerase (often also called glucose isomerase ). This enzyme converts fructose into glucose in the small intestine, but also glucose into fructose. In principle, the “glucose trick without glucose” is used here, as the fructose eaten is converted to glucose and then absorbed. The enzyme has the property of always wanting to establish a balance between fructose and glucose. This means that if equal amounts of both sugars are present, it no longer converts fructose. However, as glucose is absorbed very quickly, there is no equilibrium in the intestine and almost all the fructose can be metabolized. In theory, however, this also means that an additional intake of glucose would suppress the effect. But the glucose is absorbed so quickly that even then there is an imbalance. This means that if you take this enzyme, you don’t need any more glucose.
Recommended intake and products
Important: The enzyme is deactivated from approx. 60°C, which means you should do not open the capsules and stir them into hot food, or on vacation in the hot car! It is best to take 1-4 capsules directly before a meal rich in fructose without chewing and with plenty of water. Please always refer to the package leaflet of the respective product.
Why take an enzyme for a transport protein problem?
Fructose is transported through the small intestinal mucosa by the transport proteins GLUT-5, among others. If these transporters are missing or do not function properly, the fructose reaches other parts of the intestine, is digested by the bacteria living there and the typical symptoms occur. The orally ingested xylose isomerase intervenes beforehand and converts the fructose into glucose in the small intestine, which can then firstly also be absorbed via other transport mechanisms (GLUT-2, SGLT-1) and secondly sets the “glucose trick” in motion.
Do these remedies also help with sorbitol intolerance?
No, as described above, fructose is converted into glucose and vice versa. However, sorbitol is not metabolized. Therefore, these products do not help if you have a sorbitol intolerance. In the case of pure fructose intolerance, sorbitol can also lead to problems, as it impairs fructose absorption. This means that the little bit of fructose that someone with fructose intolerance could absorb is not absorbed, but if no fructose is present because it has been converted by xylose isomerase, sorbitol – in small amounts – does not cause any problems, even if you are fructose intolerant. This is because there is no fructose involved and small amounts of sorbitol, without having fructose in the intestine at the same time, are not a problem with fructose intolerance.
1) Rainer Klinke, Hans-Christian Pape, Stefan Silbernagl (eds.): “Lehrbuch der Physiologie”, 5th edition. Thieme, Stuttgart 2005
2) Zechmann, M; Masterman, G; “First aid after diagnosis: fructose intolerance”, Berenkamp Verlag, 2017; 5th edition