Understanding food intolerance & sensitivity

Intolerances to food are more common than true allergic reactions to food, particularly for adults. They are sometimes called food sensitivities or food intolerances.

Food intolerance is different to food allergy. Unlike food allergies, food intolerances do not involve the immune system and do not cause severe allergic reactions, known as anaphylaxis.

Food intolerance can be caused by chemicals that are found naturally in foods or by chemicals that are added to foods.  The only way to find the foods responsible for food intolerance is to follow an elimination diet and challenge procedure carefully supervised by an Accredited Practising Dietitian (APD).

There are many different symptoms of food intolerance.  These may include:

  • Hives (or rashes) and/or swellings
  • Headaches and migraine
  • Stomach and/or bowel upsets
  • Sinus and/or breathing problems.

Understanding food intolerance

People who have food intolerance react to chemicals which either occur naturally in food or are added to foods during processing. Different people will tolerate different amounts of chemicals and larger amounts cause stronger symptoms.

The amount of the chemical which causes symptoms is called the ‘dose threshold’. Some people have a high dose threshold to all food chemicals and may never have symptoms after eating foods.

Some people have a low dose threshold to food chemicals and can have unpleasant symptoms after eating foods containing a particular chemical.  This type of problem is very similar to the way that some people have side effects to certain medications.

More than one type of chemical may cause symptoms so a person may react to many different types of foods. Some foods contain the same chemicals and a person can react after eating a variety of foods that contain the same chemical. This is because the chemical slowly builds up in the body until the dose threshold is reached. It also explains why the same food does not cause symptoms every time it is eaten.

Food intolerances often run in families, suggesting a genetic predisposition. Sometimes food intolerance only affects a person after a sudden change in diet or after an illness.

Natural chemicals that may cause a reaction include:

  • Salicylates
  • Amines
  • Glutamates.

Food additives that may cause a reaction include:

  • Preservatives
  • Artificial food colours
  • Flavour enhancers e.g. MSG.
An Accredited Practising Dietitian (APD) uses an elimination diet and challenge procedure to investigate food chemical intolerance to find the chemicals responsible for symptoms. If you are experiencing symptoms from a chemical found in a food containing nutrients essential to a healthy diet, an APD can advise on the best replacement foods to ensure you still give your body the best nutrition.