Fructose malabsorption: when fruits and vegetables are unhealthy
“Pregnant belly”. That was the most accurate way I could describe how my stomach used to look after eating. Not more than a couple of hours after a meal, my abdomen was swelling to more than twice its normal size and the pain in my belly was intense. It would often last for days and despite all my best efforts to track my diet, I was unable to identify any food triggers.
In fact, the foods he was eating seemed to have completely unpredictable effects. I could eat an apple and whole grain cereal with milk for breakfast one day and have little to no problems, and the next day the same foods would give me pain and bloating in full force. The only common denominator that I could identify was the food itself.
The less I ate, the better I felt, so I began to eat as little as possible in an effort to control the pain. She often avoided social situations due to the unpredictability and potential pressure to eat, and she was losing weight. Fast. At 5’5 “I went from 130 pounds to less than 110 in a relatively short time. It became clear to me that this was not a sustainable lifestyle. The rapid weight loss, combined with a trip to the emergency room one night with The worst pain I had ever experienced prompted me to seek the help of the gastrointestinal specialist, Dr. Martin Hahn.
Dr. Hahn was instrumental in finding the source of my abdominal pain and bloating. He listened carefully to my history and symptoms and ruled out all disorders one by one: celiac disease, lactose intolerance, bacterial overgrowth, gastroparesis, gallbladder dysfunction, and the list went on. But after more than a year of testing, everything that could have caused my symptoms came back negative. Meanwhile I kept losing weight. Another doctor offered a second opinion: Try antidepressants for pain, as the cause of the pain is unknown. That was not enough for me, I wanted to discover the source of the pain and not just mask it.
Fortunately, Dr. Hahn didn’t give up on me. As we continued to work together to rule out all functional causes, as well as the most likely food allergies, Dr. Hahn encouraged me to do my own dietary research. After all, food seemed to be the only common factor in my symptoms. Not long after I stumbled upon something I had never heard of before: fructose malabsorption. The symptoms matched mine and the trigger foods were many of the foods I ate. Could this be the answer to my digestive upset?
At that time, there was no reliable evidence of fructose malabsorption. Today, some doctors advocate the use of a hydrogen breath test, similar to the lactose intolerance test, but the accuracy is still debated. Dr. Hahn encouraged me to try reducing the alleged trigger foods and see what happens. I took his advice and took the first step on my personal path to a healthy diet and lifestyle.
Fructose is a simple sugar found naturally in fruits and sweeteners like honey, and also in artificially high amounts in high fructose corn syrup. In normal individuals, fructose is absorbed from the small intestine, but in those with fructose malabsorption it is only partially absorbed. Any unabsorbed fructose travels to the large intestine, where it is rapidly fermented by bacteria. The by-products of fermentation cause varying degrees of gas, bloating, abdominal pain, constipation or diarrhea depending on the individual.
Fructose is generally well absorbed when the same amount of glucose is available at the same time. It appears that transporters that facilitate the absorption of fructose in the intestine can be up-regulated in the presence of glucose. That means free fructose can be safely consumed as long as it is balanced with an equal or greater amount of glucose. (This is not the case with hereditary fructose intolerance, a life-threatening condition in which you cannot consume fructose.)
For example, simple white table sugar (sucrose) is generally safe in moderation for people with fructose malabsorption because it contains equal proportions of glucose and fructose. In contrast, honey and high fructose corn syrup contain much more fructose than glucose per serving, so they are not safe. Supplemental glucose can be taken to compensate for excess free fructose and facilitate absorption.
However, fructose is not always in its free form. It also exists widely in the food supply in the form of fructans. Fructans are long chains of fructose with a glucose “tail” at the end. Humans do not have the enzymes to digest fructans, but the bacteria in our large intestines do. Fructans pass directly to the large intestine, where bacteria digest them into fructose molecules. Although technically not malabsorption, as the area of absorption is completely overlooked, it has the same effect, resulting in more substrate for bacterial fermentation. Fructans can be found in wheat, brown rice, garlic, onions, and many other common plant foods.
One of the biggest challenges of living with fructose malabsorption is food labeling. Many of the trigger foods are whole foods that are sold without packaging. Even if they were labeled, the necessary information would probably not be included. For example, an apple’s label might list total sugars and dietary fiber, but it would not tell the consumer that the apple contains more fructose than glucose, or that it contains sorbitol, which aggravates the effects of fructose malabsorption.
There are some lists available that detail the proportions of sugar in various foods, but they often conflict. I chose to use the lists as a guide, taking them with a grain of salt. Between the lists and a healthy dose of trial and error, I have established some personalized and effective eating guidelines for myself. My weight is stable, I can go out to eat at restaurants or friends’ houses, and I no longer avoid all social events due to the unpredictable stomach pain.
Fructose malabsorption can occur in anyone whose fructose intake exceeds their absorption capacity. It is different for each person. The level that works for me may be too much for someone else. Some foods may be safe one day and not the next, depending on the total fructose and fructan load of other foods consumed that day.
While no standard cut-off has been established, children generally have a much lower threshold than adults, and those with IBS may find that their symptoms are exacerbated by excess fructose, as the symptoms are often similar. The general rules of thumb for those experiencing symptoms of fructose malabsorption are to minimize free fructose and avoid fructans.
Now, instead of restricting my food intake, I have been able to develop my own safe and healthy way of approaching food. Eating at home is always safer because I know for sure what all my meals contain. I translate almost all recipes into my own special substitution language. “Wheat Berry Salad with Roasted Tomatoes and Asparagus” translates to “[safe grain] with [safe red vegetable] Y [safe green vegetable]. “This has made cooking and eating a much more creative (and less painful!) Experience.
Living with fructose malabsorption is still challenging at times, but I am grateful for what I have learned from it. Home cooking and clean eating are valuable skills, plus I am much more able to relate to the growing community of people with food allergies and sensitivities. By sharing our common experiences, we have the power to help each other and those around us achieve healthier and happier lives.
(C) 2013 Dawn Oulton