What are monosaccharides?
Monosaccharides are single carbohydrate molecules often known as simple sugars. Common dietary monosaccharides include glucose, galactose and fructose.
What is fructose?
Fructose, also known as ‘fruit sugar’, is a single carbohydrate molecule falling into the monosaccharide category. Unfortunately, fructose is becoming a common problem for people as intolerances are on the increase. It has been estimated that up to 70% of people suffering from IBS may have a fructose intolerance.
What is fructose malabsorption?
In order to be absorbed and put to good use, fructose must be absorbed in your small intestine. Luckily, in the small intestine there are specific transporter proteins embedded in the intestinal wall that allow for the absorption of monosaccharides across the epithelial barrier, in order for them to enter your bloodstream and be used for energy.
However, in some people it is thought that these transporters (GLUT2 and GLUT5) may be dysfunctional. The result is that fructose isn’t absorbed and travels to the large intestine where it is not well tolerated. Fructose present in the large intestine creates a feeding ground for your gut bacteria and produces symptoms such as flatulence, bloating, pain, constipation or diarrhoea. These symptoms are commonly associated with fructose malabsorption and IBS.
Fructose is in most fruits. Do I need to avoid them all?
Fructose is indeed found in most fruits and some vegetables too., However, it is found in different quantities and in different ratios to other monosaccharides, such as glucose, which is crucial in how it affects you. Try to choose foods (in particular fruit, which is a common culprit) that has the same amount of glucose as fructose, if not more. Fructose is easier to absorb and digest when it is eaten alongside glucose. The ratio of glucose:fructose should be 1:1 or greater, or else you are likely to experience symptoms. See our list of FODMAP friendly foods to help you understand what fruit and other foods are regarded as safe.
Where is fructose found?
Fructose is found naturally in many fruit and vegetables as well as honey and some more processed sweetening agents, such as fruit juice concentrate and fructose syrups.
We have produced a more extensive list of specific foods containing fructose in our High FODMAP foods section.