Getting to know

The role of the food we eat is to provide essential nutrients for the normal functioning of our body. Usually these substances have to be extracted by the body from the foods we eat and the food is processed in our digestive tract. The food we eat is first transformed into a paste by chewing and then mixed with the digestive juices produced by our digestive organs. These juices contain enzymes which digest the food and release the useful nutrients (such as proteins, carbohydrates, fats etc.) that the food contains. These nutrients cross the intestinal wall and reach the blood stream which transports them around the body. There are specific enzymes which break down the sugars, the proteins or the fats contained in food. In some people, one of these enzymes is missing because their digestive organs are not capable of producing it. Consequently, the person is not able to digest the substance which would normally be broken down by that enzyme. The undigested food irritates the digestive tract and can cause inflammation of the stomach or intestine. Unpleasant symptoms (such as nausea, abdominal cramps, vomiting or diarrhoea) will occur every time the person eats that type of food. However this reaction is not an allergy because the symptoms are caused by a defect in the functioning of the digestive tract and not by an abnormal functioning of the immune system (as is the case in allergy).

An example of food intolerance is lactase deficiency. Lactase is the enzyme that breaks down lactose, the sugar in milk. People lacking this enzyme will manifest symptoms of digestive disorder every time they drink milk or eat dairy products. 

How can you find out if your symptoms are caused by an allergy or by food intolerance? 
Some of the symptoms in both diseases can be very similar. However, a doctor can identify symptoms which are specific to one or other of the two diseases and perform tests to clearly differentiate between the two diseases. For example, a person with a milk allergy will exhibit a positive allergy test to milk; in a person with milk intolerance these tests will be negative while the tests done on fragments of the intestinal lining can prove the absence of lactase.