Fructose intolerance happens when the fruit sugar fructose is poorly absorbed in the small intestine causing symptoms of diarrhoea, bloating and wind. Fructose is not fully absorbed in most people, but does not usually give rise to symptoms.  In children and some sensitive people, too much fructose and sucrose from high intakes of certain fruits produces these unpleasant symptoms.

Malabsorption of sugars

Malabsorption describe the difficulty in digesting and absorbing nutrients from foods. Fructose Intolerance refers to the suboptimal absorption of fructose, which can arise in young children due to a limited or overwhelmed transport protein system or too much fructose in the diet. Fructose is a monosaccharide (single sugar unit)  which does not need digestion by enzymes before is can be absorbed.  Ordinary sugar, called sucrose, is a disaccharide (two sugar units) and does need digesting before it can be absorbed.  Sucrose is made of one fructose unit and one glucose unit and so sugar itself may give rise to similar symptoms.

What are the symptoms?

Fructose that passes into the large intestine unabsorbed in the small intestine, is fermented by the intestinal bacteria into gases and acids.  This causes a number of unpleasant symptoms including bloating and flatulence caused by the production of gas, sometimes abdominal pain due to bloating and diarrhoea or urgent, explosive, watery stools.

Dietary treatment 

The treatment is a diet low in fructose; achieved by reducing fruit and vegetable intakes, especially fruit juices, dried fruit and honey. It is not possible to exclude fructose from the diet completely and because fruits and vegetables are part of a healthy diet, should be reintroduced in a controlled way once symptoms have completely resolved.