Fructose Malabsorption: A Very Frequent Problem

8 Apr 2018

How often do we suffer from gas, bloat, nausea, cramping and diarrhea or know of someone with similar symptoms? At least one in every eight people suffer from these symptoms on a rather regular frequency. While the causes of these symptoms can be caused by a number of reasons such as celiac disease (gluten allergy), giardia, pancreatic insufficiency, inflammatory bowel disease, H. pylori gastritis, lactose intolerance and the like, many of us suffer from an intolerance/malabsorption to fructose. We cannot absorb this sugar in the small intestine so it passes into the colon where our bacteria ferment it and generate the symptoms.

It is unclear how many of us suffer from fructose malabsorption but it is more common than one might think. I see many patients complaining of symptoms like those listed above. Some studies suggest that as many as 40% of us do not absorb this sugar. I find one to two individuals weekly who suffer from this malady. While I have a bit of a biased group of patients that I am testing, my results show at least 90% of my symptomatic individuals suffer from fructose malabsorption.
Fructose, also known as fruit sugar, is incompletely absorbed in many of us for unclear reasons. Because of this, when we eat a couple slices of watermelon, or a banana or apple and get a “bellyache,” fructose is typically the cause of our symptoms. Likewise; honey, fruit juices, high fructose corn syrup or sugar- sweetened beverages can cause the same symptom complex.

A test has been developed to see if we are suffering from fructose malabsorption. This is a breath test where the patient breathes into a bag and has it analyzed for hydrogen and methane production after ingesting a prescribed dose of fructose. If we adequately absorb the fructose, none of it makes its way into the colon where it would generate symptoms from bacterial fermentation and gas production of the sugar. Likewise; if we do not absorb fructose, the colon fermentation will generate one or both of these gases that can then be detected in our breath because they rapidly diffuse from the colon into the bloodstream, are carried to the lungs and are then expired in our exhaled breath. The breath test can accurately measure these expired gases if our colonic bacteria are fermenting the fructose and generating the gases.

If you look at the diagram below of three different fructose breath test results, you will see a rise in the gas production a short time after fructose is ingested. Often, symptoms that I listed above will also ensue and there is immediate reinforcement of symptom reproduction with fructose malabsorption in the patient’s mind. Some people will only generate a small amount of gas and symptoms, as seen on the left, while the others will generate a massive amount as seen on the far-right individual result.

So, if you suffer from what many health care providers label as irritable bowel syndrome but no one can figure out why, consider whether your symptoms could be due to fructose malabsorption. Once you know that you suffer from this malady, you can then make dietary changes to diminish your symptoms. The big five sources of fructose include: honey, table sugar, high fructose corn syrup, many fruits and fruit juice. There are also a few vegetables that contain higher levels of fructose. These include: sugar beets, sweet potatoes, sweet corn and sweet peas. Reducing these sources of fructose can make fructose malabsorbers feel much better long term.

Dr. M. Frank Lyons
References: Fructose Exposed, MF Lyons, 2010; Lyons Lifestyle, MF Lyons, 2016.