What is Fructose Malabsorption? Is It The Same As Fructose Intolerance?

By Amy Burkhart MD, RD

Fructose malabsorption may be causing your stomach problems. What is it? Is it the same as fructose intolerance? The internet may have you wondering. Let’s clear up the confusion..

Fructose is in many foods

Fructose is a sugar found in many foods such as fresh fruits and honey, high fructose corn syrup, and many processed foods. It is also a component of plain table sugar and some vegetables.

People with fructose malabsorption can not digest fructose

Some people cannot completely absorb fructose in their small intestine-the beginning part of the digestive tract. The undigested fructose is then carried to the colon, where our normal bacteria rapidly devour it. In the process, the bacteria produce gases that cause the intestine to swell. This is experienced by the person as bloating, cramping, gas, and distention. Diarrhea may also occur due to the undigested particles of fructose.

Fructose intolerance is VERY different from fructose malabsorption.

Hereditary fructose intolerance occurs in infants, is genetic, and can lead to severe health problems such as liver disease, seizures, and mental retardation. The names are similar, but the entities are VERY different. There is no cure for hereditary fructose intolerance, but it is manageable. A fructose-free diet is followed for life. The confusion occurs because fructose malabsorption is at times referred to as DIETARY fructose intolerance. To eliminate confusion, the term hereditary fructose intolerance should be used.

It mimics other conditions

The symptoms of other disorders, such as celiac disease and non-celiac gluten sensitivity (NCGS), can be very similar to fructose malabsorption symptoms. Thus, the diagnoses’ may often be confused or difficult to make. Fructose malabsorption can also mimic lactose/milk intolerance, IBS, SIBO, IBD, FODMAP intolerance, and more.  Fructose malabsorption (FM) may also be seen with celiac disease or NCGS and should be considered in these patients who are already on a gluten-free diet yet have ongoing symptoms. It needs to be thought of intentionally, or it is easy to miss.

Symptoms depend on amount eaten

The onset of symptoms can occur at any age.  Some people can tolerate much more fructose than others. The most common symptoms are bloating, gas, cramping, and diarrhea. When diarrhea occurs over prolonged periods, nutrient deficiencies and their symptoms may appear. The most common nutrients affected are folic acid, zinc, iron, tryptophan, calcium, vitamin c, and e. Elevated blood levels of amylase and lipase enzymes from the pancreas- may also be seen. Some people may also experience fatigue, headaches, brain fog, mood changes, and constipation.

A breath test is used to check for FM

The standard test done to evaluate for fructose malabsorption is called a Fructose Malabsorption Breath Test. This is a simple test that can be done in the office and requires no blood to be drawn. Some patients choose to start with a fructose elimination diet instead of a breath test. This is best done in conjunction with a dietitian familiar with fructose malabsorption to assure the diet is initiated properly, and adequate nutrition is maintained during the elimination period. If fructose malabsorption is the problem and the diet is done correctly, it often yields good results. If the elimination diet does not yield clear results and fructose malabsorption is still considered, the breath test should be performed.

The treatment for fructose malabsorption is a low-fructose diet.

The diet limits foods containing high amounts of fructose.

Some examples of high-fructose foods include fruit, sweeteners, honey, juices, high-fructose corn syrup, and corn syrup solids.

A complete LOW FRUCTOSE DIET HANDOUT is found here,

The Low FODMAP diet lowers fructose intake

The  Low FODMAP diet is most commonly used for IBS and SIBO and other digestive disorders such as inflammatory bowel disease. The low FODMAP diet does limit fructose, but it also eliminates other sugars/carbohydrates. It is much more restrictive than the low fructose diet. It will help fructose malabsorption, but it typically is more limiting than a person with fructose malabsorption needs.

Low FODMAP diet 

FODMAP stands for “ Fermentable, oligo-di and monosaccharides and polyols.”

A low FODMAP diet eliminates:

1. Lactose-the milk found in cow, sheep, and goat milk
2. Fructose- eg. apples, figs, pears, watermelon
3. Fructans– A form of fructose found in wheat and vegetables. The most common vegetables are onions and garlic. Other common fructans are inulin and fructooligosaccharides (FOS). These are found in many probiotics and “nutrient fortified” foods.
4. Galactans– a carbohydrate found in beans, pistachios, cashews
5. Polyols– A sugar alcohol. The most common are the artificial sweeteners sorbitol, xylitol, and mannitol.

Everyone has a different tolerance level for fructose

If you have fructose malabsorption, it is recommended to eliminate fructose for 4-6wks. And then re-introduce fructose-containing foods one at a time every four days. Each individual will find their own tolerance level for dietary fructose. If your symptoms have subsided on a low fructose diet and they return upon reintroduction of food. You have found your sweet spot! The best news is you may have also found the answer to your digestive woes!

• Fructose Malabsorption And Irritable Bowel Syndrome (IBS)- https://pubmed.ncbi.nlm.nih.gov/32122419/
• Fructose Breath Test And IBS-https://pubmed.ncbi.nlm.nih.gov/31113646/
• Fructose Malabsorption In Inflammatory Bowel Disease-https://pubmed.ncbi.nlm.nih.gov/32643952/
• Effects Of Low Lactose, Or Fructose Or Low Sorbitol On The Microbiome-https://pubmed.ncbi.nlm.nih.gov/32643952/
• Histamine In Functional Bowel Disorders-https://pubmed.ncbi.nlm.nih.gov/32643952/