Letzte Aktualisierung am 9. September 2024 von Dr. Michael Zechmann-Khreis
In intestinal fructose intolerance, the GLUT-5 transporter presumably does not function properly or too few such transporters are present. The exact cause is not yet fully understood. In any case, the fructose is not sufficiently absorbed in the small intestine, remains in the intestine and reaches the next section of the intestine, the large intestine. There, various bacteria metabolize the fructose into gases such as hydrogen (H₂₂), CO₂ and short-chain fatty acids. This is where the symptoms of fructose intolerance develop.
The hydrogen does not cause any symptoms, but is used for diagnosis by means of an H₂ breath test. The CO₂ leads to flatulence and abdominal pain. The short-chain fatty acids create an osmotic gradient, which causes an imbalance in the local water balance and thus favors the penetration of fluid into the intestinal lumen. This leads to watery diarrhea, a typical symptom of fructose intolerance.
Some types of bacteria produce methane, which “paralyzes” the intestines and causes constipation, which is also a symptom of intestinal fructose intolerance.
The most common symptoms of fructose intolerance
- Flatulence
- Abdominal pain
- Diarrhea
- Nausea
Many other symptoms can also occur. These include:
- Reflux & heartburn | Facebook group on this topic
- Tiredness, fatigue
- Depressive moods (NOT depression!) have been reported, the connections are still unclear, contrary to some internet reports
- Headaches (up to and including migraines)
- …
The severity of the symptoms of fructose intolerance varies greatly and can vary from day to day. One day you can tolerate a few strawberries, the next day they give you diarrhea. If you are fructose intolerant, the trick is to slowly approach your body and learn to listen to it.
Delayed onset of symptoms with fructose intolerance
Another problem is the time delay of the symptoms. Some patients report that symptoms only appear 24 to 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 about 10 to 20 minutes.
You can find out how to treat fructose intolerance and its symptoms here.
Sources
1) Rainer Klinke, Hans-Christian Pape, Stefan Silbernagl (eds.): “Lehrbuch der Physiologie”, 5th edition. Thieme, Stuttgart 2005
2) Zechmann, M; Masterman, G; “Erste Hilfe nach der Diagnose: Fruktoseintoleranz”, Berenkamp Verlag, 2017; 5th edition
3) Benardout, M., Le Gresley, A., ElShaer, A. & Wren, S. P. Fructose malabsorption: causes, diagnosis and treatment. Br.
J. Nutr. 127, 481-489 (2022).
4) Survey of affected persons (n=802) on the nmi portal, 2018
