Food Allergy & Intolerance Tests

Lactose, a disaccharide, is not normally absorbed directly from the gut, but is broken down into glucose and galactose by the enzyme lactase. If the lactase is absent (or insufficient for the dietary load of lactose), then non-absorbed lactose will be the pass into the lower small intestine and the colon. This may result in diarrhoea with cramps and flatulence, the symptoms of the condition known as “lactose intolerance”, which is not an allergic condition but a digestive problem.

In such cases, the lactose, on reaching the large bowel is fermented by colonic bacteria producing hydrogen and sometimes methane.  These gasses pass across the gut wall into circulation and are exhaled in the breath.

This test requires the collection of breath samples after avoiding dietary fibre, resistant starch, complex carbohydrates and dairy products for 24 hours, followed by an overnight fast.  An initial breath sample is collected, the patient then consumes 25G of lactose (supplied with the test kit) and then further breath samples hourly for three hours.  A negative test will return very low levels of hydrogen and methane throughout, whereas a patient with lactose intolerance will exhibit raised levels of breath gasses when the lactose reaches the colon, as illustrated in the sample report which can be viewed below.

Test datasheet: Lactose Intolerance datasheet

Sample report:  Lactose Intolerance Breath Test sample report

Patient instruction sheet:  Lactose Intolerance Breath Test patient instructions.

Fructose is a simple monosaccharide found in many plant foods and is widely used as a sweetening additive in the form of fructose corn syrup, a mixture of glucose and fructose. Its consumption has risen in recent years.

Non-absorbed fructose produces gastrointestinal symptoms in the large bowel when metabolised by colonic bacteria, which may be a cause of recurrent abdominal pain. It has also been suggested that fructose malabsorption may underlie the gastrointestinal symptoms seen in patients with irritable bowel syndrome (IBS) [2].  Genetic mutations can increase an individual’s susceptibility.

Breath testing is the method of choice for the diagnosis of fructose intolerance.  25 g of fructose is the cut-off dose to investigate fructose malabsorption, with a positive breath test at this dose suggesting poor fructose absorption capacity.  This low level may be regularly consumed in the daily diet, resulting in frequent symptoms of fructose malabsorption [4].

Fructose malabsorption should be considered in subjects with unexplained gastro-intestinal symptoms, especially after consumption of fruit and fruit drinks. Fructose malabsorption may also contribute to the symptoms of IBS.

Test datasheet: Fructose Intolerance datasheet

Sample report:  Fructose Intolerance Breath Test sample report

Patient instruction sheet:  Fructose Intolerance Breath Test patient instructions.