Understanding Fructose & Fructose Malabsorption
IBS Awareness Month, Week 3
Fructose malabsorption and IBS
Fructose malabsorption can occur in people with or without Irritable Bowel Syndrome (IBS).
About 1 in 3 people experience symptoms of IBS have fructose malabsorption.1 The effect of fructose malabsorption is exaggerated in people with IBS compared with those without IBS.1,2
What is fructose and where is it found?
Fructose is a Monosaccharide (a type of simple carbohydrate) that occurs naturally in a variety of foods. It is found as free fructose in honey, certain fruits (such as apples, pears and mangoes).3,4
Fructose is sweet to taste, and it is a common ingredient that is often added to many American food products in the form of high-fructose corn syrup (HFCS). In the USA, you can find HFCS in many soft drink and processed food products.
How is fructose digested in the gut?
Fructose is absorbed in our small bowel, however, generally humans have a limited absorptive capacity for fructose.3
Fructose malabsorption occurs when the small bowel incompletely absorbs fructose.1 Similar to other FODMAPs, the unabsorbed fructose combines with water and is rapidly propelled into the large bowel, where gut bacteria ferment fructose to carbon dioxide, hydrogen, and short-chain fatty acids. This produces a laxative effect and causes rapid gas production, leading to distention, bloating, abdominal discomfort, and increased gut motility.1
Interestingly, fructose absorption is coupled with that of glucose (another simple carbohydrate found in many type of grain products, fruits and vegetables). Glucose facilitates fructose absorption in the gut. Excess fructose refers to the fructose in excess of glucose in food. To prevent or reduce symptoms, research has suggested that the optimal ratio of glucose-to-fructose in food for people with fructose intolerance to be 1:1.1,2,5 Foods that contain large amount of excess fructose can lead to malabsorption problems that are often exacerbated in people with IBS.2
This infographic may help you to understand the glucose-to-fructose ratio:
How is fructose intolerance tested and diagnosed?
Fructose intolerance refers to the presence of fructose malabsorption and the associated reoccurrence of the unpleasant gastrointestinal symptoms.
The best way to determine the presence of fructose intolerance is to undergo dietary fructose elimination and re-introduction with an Accredited Practising Dietitian (Australia) or a Registered Dietitian (US, UK, etc…).
The breath hydrogen and methane test is also available as an investigation test to detect fructose malabsorption. When accompanied by gastrointestinal symptoms, fructose intolerance may be indicated when hydrogen and methane levels of breath meet a certain criteria following the oral consumption of standard dose of fructose.3
However, small intestinal bacterial overgrowth (SIBO) can also be a cause for unexplained gastrointestinal symptoms therefore it should be considered before confirming a diagnosis of fructose intolerance.
What is prevalence of fructose malabsorption and intolerance?
There are two forms of fructose intolerance – Hereditary fructose intolerance and Incomplete fructose absorption.
Hereditary fructose intolerance (HFI) is a rare metabolic disease caused by the absence of an enzyme called aldolase B. In people with HFI, ingestion of fructose causes low blood sugar levels and the build-up of dangerous substances in the liver.6
Incomplete fructose absorption is the more common form of fructose intolerance when our small bowel malabsorbs fructose as discussed earlier. In this blog, fructose intolerance refers to incomplete fructose absorption.
According to the Food Intolerance Institute of Australia, up to 1 in 3 people have some level of sugar intolerance – most common one being fructose.2 It is difficult to determine the exact prevalence of fructose intolerance in the general population because fructose intolerance is still relatively new to be researched.
Among the US populations, it is suggested that a rise in fructose consumption has led to a rise in fructose malabsorption and intolerance.4
Which food are high in fructose?
Although reducing consumption of fructose can reduce occurrence of the unpleasant symptoms in people with fructose intolerance, it is unnecessary to eliminate all food containing fructose because the concern is only the consumption of food containing fructose in excess of glucose.
Rather, those affected should reduce intake of foods that are high in excess fructose that trigger their symptoms, and replace them with alternatives that they tolerate better.
Below we have listed some examples of foods that are high in excess fructose and also some examples of foods containing glucose in balance with, or in excess of, fructose:
The percentages of fructose per serve of each food items listed in the above table, are tested as shown in the FODMAP Friendly App.
The degree of fructose malabsorption hence the upper tolerable quantity of fructose in the diet may vary from person to person. An Accredited Practicing Dietitian or other FODMAP trained expert should be consulted in order to help develop an appropriate and nutritionally adequate diet plan.
It should also be noted that the foods that are low in fructose can still contain other FODMAPs. If you have IBS and want to be 100% sure which particular FODMAPs are in your food, use the FODMAP Friendly App as a guide!
About the next blog…
We’ll help you navigate food ingredient labels so that you’ll be able to spot high fructose ingredients that are commonly found in the food supply. We’ll also provide a tasty low FODMAP low fructose recipe!
Thanks for reading!
References:
- Shepherd SJ, Gibson PR. Fructose Malabsorption and Symptoms of Irritable Bowel Syndrome: Guidelines for Effective Dietary Management. J Am Diet Assoc. 2006 Oct;106(10):1631-9.
- The Food Intolerance Institute of Australia. Fructose Intolerance – Frequently Asked Questions [Internet]. Australia: foodintol; 2010 [updated 2017 Aug 22; . cited 2018 Apr 10]. Available from: https://www.foodintol.com/fructose-intolerance
- Amy F, Satish SCR. Dietary fructose intolerance, fructan intolerance and FODMAPs. Curr Gastroenterol Rep. 2014 January ; 16(1): 370
- Montalto M, Gallo A, Ojetti V, Gasbarrini A. Fructose, trehalose and sorbitol malabsorption. Eur Rev Med Pharmacol Sci. 2013;17 Suppl 2:26-9.
- Marie EL, Suzanne MS. Fructose Malabsorption and Intolerance: Effects of Fructose with and without Simultaneous Glucose Ingestion. Crit Rev Food Sci Nutr. 2011 Aug; 51(7): 583–592.
- National Center for Advancing Translational Sciences. Hereditary fructose intolerance [Internet]. US: NIH; 2015 [updated 2015 Aug 20; cited 2018 Apr 16]. Available from: https://rarediseases.info.nih.gov/diseases/6622/hereditary-fructose-intolerance
Eat with Confidence!
