Food intolerance

Food intolerance is difficulty digesting certain foods and having an unpleasant physical reaction to them. Dr Mark Austin is here to describe these reactions and their causes in further detail. 

What are the main signs of a food intolerance?

The main symptoms of food intolerance are:

• abdominal pain
• diarrhoea
• nausea and/or vomiting
• bloating, burping or flatulence
• nasal congestion
• tingling or itching in the mouth
• mouth ulcers
• eczema
• difficulty swallowing

What tests are available?

A number of companies provide food intolerance tests, but these tests are not based on scientific evidence or recommended by dieticians or the British Dietetic Association. These tests are either a finger prick test or blood test measuring potential allergy proteins in the blood. 

The best way of trying to identify food intolerances or sensitivities is to complete a food diary monitoring symptoms following the ingestion of particular foods. These foods can then be removed from the diet and later reintroduced whilst monitoring symptoms.

With the food diary, write down which food groups are eaten, symptoms suffered after eating these foods and when these symptoms happen.  The next step is to embark on an elimination diet cutting out one of the problem foods one at a time. The elimination diet needs to continue for at least 2-6 weeks.

What are the main causes of food intolerance?

The commonest causes of food intolerances are dairy or lactose intolerance. This suggests that the body cannot digest lactose - a sugar found naturally in milk, yoghurt and soft cheeses. 

Some people may also have trouble digesting wheat, Symptoms are classically bloating, cramps and possibly diarrhoea, all of which generally occur hours after eating. Other abdominal symptoms can be caused by fermentation of simple sugars found in milk and certain fruits and vegetables. These can be addressed by initiating a low FODMAP diet with the help of a dietician.

What are the most common food intolerances?

Food allergies in adults include fish, shellfish, nuts, milk, eggs and peanuts. These are often a reaction of the immune system. The immune system mistakenly recognises proteins found in food as allergens. These then trigger an immune-mediated reaction resulting in wheezing and itching with rapid onset and can be life-threatening. 

What is the difference between food intolerance and food sensitivity?

Food intolerance does not generally involve the immune system or manifest an allergic reaction, nor are they usually life-threatening. It will generally happen a few hours after eating food. It usually requires eating a normal amount of the problematic food rather than just a trace of it.

Food sensitivity (or allergies), on the other hand, occur as a result of the immune system overreacting to a certain protein. It only takes a small amount of a problematic food to trigger an allergic reaction.

Gluten intolerance is a good example, it causes abdominal pain and bloating following eating a reasonable amount of wheat. Those with coeliac disease who are allergic to gluten only need to eat a trace of gluten before they suffer significant symptoms.

For further information about food intolerance, or consultation about your own digestive problems, visit Dr Austin's Top Doctors Profile.