Celiac Disease and Associated Fructose Malabsorption

Celiac Disease and Associated Fructose Malabsorption



I had been following a strict gluten free diet, and had recently been diagnosed with lactose intolerance. In order to quickly eliminate any residual symptoms, and to kick start the healing of my small intestine I was following a completely raw vegan diet, eating only raw fruits, vegetables and seeds. However, the diet had quite the opposite effect, and my gastrointestinal (GI) symptoms went into overdrive. After every meal I had nausea, severe abdominal swelling / bloating, abdominal pain, diarrhoea, headaches, and lethargy. The symptoms were similar to having consumed gluten, but I was on a strict gluten free diet, so I was absolutely certain that it couldn’t be gluten. Although the physical symptoms were the same, I was experiencing additional psychological symptoms. At the time I thought I was just feeling defeated and dejected, but it progressively worsened, to the point of severe mood swings, anxiety and depression.

Fructose malabsorption was a condition I had heard of, but I only had a vague idea what it was and I certainly didn’t know anyone who had it. It wasn’t until a chance discussion with a friend did I realise that it’s a condition closely associated with celiac disease. As I found out more, I dawned on me that my symptoms were most likely a result of fructose malabsorption, and the mood swings and depression were caused by an imbalance of Tryptophan in my body from excess fructose. Within a week of implementing a low fructose diet all of my GI and psychological symptoms had disappeared. I felt so much better, physically and mentally.

Predictably, neither my doctor or dietician even suggested fructose malabsorption as a possible cause, despite my ongoing GI symptoms. I admit, at this stage I am completely self-diagnosed and my symptoms are self-managed. I am still trying to decide whether to undergo the necessary hydrogen breath test to formally diagnose fructose malabsorption.

My journey with fructose malabsorption is still in its infancy, I am still learning how to manage and balance this condition along with celiac disease and lactose intolerance. In order to give myself the best chance of health and happiness I have tried to find out as much as I can about the condition. 


Fructose is a simple monosaccharide or carbohydrate3, 2  found in many plants and fruits4 and is commonly referred to as fruit sugar. In a healthy individual, the fructose is absorbed in the small intestine and an enzyme (fructose 1-phosohate aldolase), produced in the liver, converts the fructose to fructose-1-phosphate, which is further metabolised to glyceraldehyde-3-phosphate2. This metabolism of sugars is the primary energy generating mechanism in the body2

There are two very distinct types of fructose malabsorption, Hereditary Fructose Intolerance (HFI) and fructose malabsorption2. Both are metabolic disorders and often incorrectly described as fructose allergies2, 1. HFI is an inherited metabolic condition, and is NOT associated with celiac disease.

Fructose Malabsorption

Fructose malabsorption is where ingested fructose is not absorbed in the small intestine and subsequently enters the large intestine2, 3, 5.  Residing bacteria in the large intestine rapidly ferment the sugars to acids and gases, predominately hydrogen, methane and carbon dioxide2, 3, 1, 4. The gases released from the bacteria are the causes of the GI symptoms and include diarrhoea, severe abdominal swelling/bloating, abdominal pain , flatulence2, 1, 5 heartburn, headaches, tiredness and lethargy, mood swings, anxiety, disturbed sleep patterns1, 4 and craving of sweet foods1.  As with lactose intolerance, fructose malabsorption can occur in celiac patients1, 4 due to the damaged villi in the small intestine no longer being capable of absorbing fructose.

Tolerance Levels

The threshold for symptoms varies greatly amongst individuals1, some having issues with less than 1 gram of fructose, while others can tolerate 10 grams1 or 20 grams without problems2, 4. Once fructose has been ingested, after the immediate symptoms of stomach pain, abdominal bloating and cramps, it can take up to three days for your body to break down the fructose, during which time you may experience symptoms such as mood swings, disturbed sleep and tiredness1. It has also been suggested that fructose malabsorption may underlie the GI symptoms seen in many Irritable Bowel Syndrome (IBS) patients3, 4 where these symptoms are often misdiagnosed as IBS1. There is limited information on fructose malabsorption in the UK yet it is estimated that 30-40% of Europeans may suffer from it2, 4. If you suffer from IBS, it may be worth asking your doctor for fructose malabsorption and lactose intolerance testing.


Fructose malabsorption can be diagnosed using the hydrogen breath test 2, 3, 1, 4. Hydrogen is not a natural by-product of digestion, but is produced by the large intestine with the introduction of fructose. Hydrogen can be detected in the breath of a fructose intolerant individual within 1 hour of ingesting fructose on an empty stomach2. The test is typically performed after a 14 hour fast.


The treatment for fructose malabsorption is a fructose free diet or a low fructose diet, depending on the individuals tolerance threshold2. FODMAP is an acronym for Fermentable Oligo-, Di- and Mono-saccharides And Polyols1, 5. It has been suggested that following a low FODMAP diet is the best way to manage fructose malabsorption1

Australian researcher Dr Sue Shepherd5 developed the low FODMAP diet in 1999 where she proved that limiting dietary FODMAPs was an effective treatment for IBS and it is now accepted as the most effective dietary treatment for IBS5 and fructose malabsorption6. Foods that contain a high fructose to glucose ratio are considered FODMAPs6. A few examples, but by no means exhaustive, of food sources for each of the FODMAPs are listed below taken from the Shepherd Works website5, 7:

  • Monosaccharides (Excess Fructose): Honey, Apples, Mango, Pear, Watermelon, High Fructose Corn Syrup, Corn Syrup Solids
  • Oligosaccharides (Fructans): Artichokes (Globe), Artichokes (Jerusalem), Asparagus, Beetroot, Chicory, Dandelion leaves, Garlic (in large amounts), Leek, Onion (brown, white, Spanish, onion powder), Raddicio lettuce, Spring Onion (white part), Wheat (in large amounts), Rye (in large amounts), Inulin, Fructo-oligosaccharides.
  • Disaccharides (Lactose): Milk, ice cream, custard, dairy desserts, condensed and evaporated milk, milk powder, yoghurt, margarine, soft unripened cheeses (e.g. ricotta, cottage, cream, marscarpone).
  • Galacto-Oligosaccharides (GOS): Legume beans (e.g. baked beans, kidney beans, bortolotti beans), Lentils, Chickpeas.
  • Polyols: Apples, Apricots, Avocado, Cherries, Longon, Lychee, Nectarines, Pears , Plums, Prunes, Mushrooms, Sorbitol (420), mannitol (421), xylitol (967), maltitol (965) and Isomalt (953).

Consumption of foods containing an equal proportion of fructose and glucose, or more glucose than fructose, will facilitate the absorption of  fructose. However, the inclusion of any sorbitol in the same meal, will act to lower fructose tolerance62. Some fruits high in sorbitol are: apples, apricots, gooseberries, grapes (raisins), strawberries, raspberries, plums, peaches and juices from all these fruits2, 4. Non carbohydrate sweeteners such as aspartame, acesulfam K, saccharin, cyclamate, thaumatin do not appear to cause any problems for individuals with fructose malabsorption2

There is very little data currently available regarding nuts, nut butter, coconut, dark chocolate and cocoa powder but they are likely to contain fructans6.  The leader in FODMAP analysis at Monash University in Melbourne have indicated that pistachios, flaxseeds, almonds and hazelnuts are also FODMAPs6.

It is recommended to eat little and often, five small meals a day, to help maintain a constant blood sugar level1. It is important not to overload on ‘safe’ FODMAP fruits, i.e. those deemed to have a safe fructose to glucose ratio. As this will increase the overall quantity of fructose within the meal, and may cause GI symptoms6. Not every food containing fructose causes symptoms within individuals with fructose malabsorption3 so it is important that you establish your personal tolerance levels. This will ensure that you do not exclude foods from your diet unnecessarily8. A good starting point would be to avoid foods containing excess fructose, dietary sources of fructans and maintain a low fructose load7. The majority of gluten free and other ‘free from’ foods contain ingredients incompatible with a FODMAP diet, so finding a balance can be difficult. 

Do you suffer from fructose malabsorption? I’m still learning so I’d love to hear your experiences.

You can now listen to this post as a Podcast directly below:

Medical Disclaimer


  1. Fructose Intolerance, Irritable Bowel Syndrome, and the FODMAP Diet. http://ndnr.com/web-articles/gastrointestinal/fructose-intolerance-irritable-bowel-syndrome-and-the-fodmap-diet/
  2. Fructose Intolerance/Malabsorption and HFI. http://www.food-info.net/uk/intol/hfi.htm
  3. Biolab Medical Unit. Nutritional and Environmental Medicine. http://www.biolab.co.uk/index.php/cmsid__biolab_test/Breath_hydrogen_&_methane_-_Fructose_intolerance
  4. Gastroenterology Consultants – A Family of Healing Partners. Fructose Intolerance. http://www.gastroconsultantsqc.com/services/diseases/fructose-intolerance/
  5. Low FODMAP Diet. Shepherd Works. http://shepherdworks.com.au/disease-information/low-fodmap-diet
  6. Fructose Malabsorption, FODMAPs and the Paleo Diet. http://www.eat-real-food-paleodietitian.com/paleo-diet-and-fodmap.html
  7. Shepherd works. Fructose Malabsorption. http://shepherdworks.com.au/disease-information/fructose-malabsorption
  8. Figureate, Food, Nutrition and Fitness. Accredited Practising Dietitians. http://www.figureate.com.au/main/page_side_nav_food_intolerancefodmaps.html 

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