I had never heard of fructose malabsorption until my gastroenterologist diagnosed me with it about three years ago. This is probably not surprising being that is not a well-known digestive disorder even though it is estimated that 30-40% of people suffer from it. Unfortunately, it took about six years from my initial complaint to my physician until I was properly diagnosed. Part of the reason it took so long was that many of the symptoms of fructose malabsorption are similar to other digestive disorders, such as irritable bowel syndrome, lactose intolerance, Crohn’s disease, ulcerative colitis, and celiac disease. In my attempt to prevent someone else from waiting six years to be diagnosed, below is some information on fructose malabsorption, its symptoms, and diagnostic tests.
Fructose malabsorption occurs when the small intestine is unable to absorb all of the fructose we consume into the bloodstream to be processed and used by our body. It is not certain what prevents the proper absorption of fructose, but studies indicate that it may be due to the limitation of how much fructose can be transported at one time by GLUT5. GLUT5 is a protein located in the walls of the small intestine known to transport fructose from the intestinal lumen into the bloodstream. If the small intestine is unable to absorb the fructose, the fructose combines with water and moves into the large intestine where bacteria feeds off of it, resulting in fermentation. This produces carbon dioxide, hydrogen, methane, and short-chain fatty acids, which can lead to bloating, distension, abdominal pain, change in motility, which can then result in diarrhea or constipation and cramping. Additionally, there may be growth of a mucosal biofilm, which can lead to inflammation. Other possible symptoms are abdominal pain, nausea, vomiting, reflux, fatigue, brain fog, joint pain, nutritional deficiencies, weak nails, and depression. The inflammation and nutritional deficiencies can cause the brain fog, fatigue, and joint pain. It can also lead to weight gain. The depression may be due to the presence of fructose in the large intestine resulting in the degradation of tryptophan, an amino acid that is important in the production of the neurotransmitter serotonin, which is a known mood enhancer. My specific symptoms were bloating, gas, constipation, cramps, nausea, brain fog, fatigue, joint pain, weak nails, weight gain, vitamin D deficiency, and pain behind my eyes. I only found one reference about the pain behind my eyes and when I mentioned it to my doctor he said it can happen but it is extremely rare. Lucky me!
The best way to figure out if you have fructose malabsorption is a hydrogen breath test. To help your doctor determine if a hydrogen breath test should be performed, it is recommended to maintain a list of what you eat, how you feel after you eat specific foods, and your bowel movement afterwards. Physicians may also want to perform other tests to eliminate other possibilities such as lactose intolerance, bacterial overgrowth, or cancer. When I was going through tests to figure out what was causing my digestive issues, I had an ultrasound, CAT scan, colonoscopy, and two breath tests before it was discovered that fructose malabsorption was the culprit.
The hydrogen breath test is used to assay for fructose malabsorption, lactose intolerance, and bacterial overgrowth. If one absorbs fructose properly, the body should not produce much or any hydrogen. If one has fructose malabsorption, then the bacteria in the large intestine will produce hydrogen and methane after ingesting fructose. The hydrogen and methane will move through the bloodstream and then into the lungs. Doctors can monitor the levels of these two gases present in your breath via gas chromatography. The test involves breathing into a balloon type bag. The air from the bag is then injected with a syringe into a gas chromatograph to establish a baseline. The patient then drinks a solution of fructose and breathes into the bag every fifteen minutes over a total of 2 to 3 hours. A certain level of hydrogen or methane indicates that one has fructose malabsorption. There can be false results, some patients do not release hydrogen from their lungs, and some do not contain hydrogen-producing bacteria in their intestine. However, right now, the breath test is the best available way to diagnose fructose malabsorption. Another way would be to eliminate the trigger foods and see if the symptoms go away. One step further would be to then reintroduce fructose and other trigger foods to see if the symptoms return.
Having fructose malabsorption does require a change in one’s diet. My doctor recommended that I work with a nutritionist to learn about the low FODMAP diet and I was put on a vitamin D supplement. The low FODMAP (fermentable oligo-, di-, monosaccharides and polyols) diet, was designed by Dr. Sue Shepherd for patients with irritable bowel syndrome. The diet includes foods that contain fructose, fructans, which are chains of fructose and found in onions, garlic, and wheat, galactans, which are chains of the monosaccharide galactose and found in kidney beans and chick peas, polyols, which are also known as sugar alcohols used as a sweetener, and lactose, which is found in dairy products. After working with a nutritionist and some trial and error, I now have a good understanding of what I can and cannot eat. I still have some bad days when I feel sick but I can usually tie it back to something I ate and I know how to heal my stomach to get back to normal.
Being sick for so long is difficult both physically and psychologically, which is why being diagnosed as soon as possible is so important. If you think you may have fructose malabsorption, start keeping a food log and talk to your doctor about the hydrogen breath test.
Do you have fructose malabsorption? How do you manage your symptoms?
1. Däbritz, J et. al (2014) Significance of hydrogen breath tests in children with suspected carbohydrate malabsorption. Biomed Central, 14(59): 1471-2431
2. Wilder-Smith, C.H., et. al (2013) Fructose and lactose intolerance and malabsorption testing: the relationship with symptoms in functional gastrointestinal disorders. Alimentary Pharmacology and Therapeutics, 37: 1074–1083
3. Lozinsky, A.C., et. al (2013) Fructose malabsorption in children with functional digestive disorders. Arquivos de Gastroenterologia, 50(3): 226-230
4. Jones, H.F., et. al, (2010) Intestinal fructose transport and malabsorption in humans. Am J Physiol Gastrointest Liver Physiol, 300: G202–G206
5. Gibson, P.R. et. al, (2007) Review article: fructose malabsorption and the bigger pictureAlimentary Pharmacology & Therapeutics, 6. http://www.webmd.com/digestive-disorders/news/20030714/fructose-may-cause-digestive-problems
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