Identifying Food Intolerance
by Bronwen de Klerk

You may find that you don't feel too good after eating certain foods, but if you were to go to a doctor for an allergy test for the foods you suspect are making you feel off-balance, you would probably find that they wouldn't show up as allergens. Let me explain a little more about this.

There are two different types of responses by the body's immune system when an offending food (an allergen) is eaten:

1. The more extreme type of response is the release of antibodies called IgE. This IgE antibody triggers the release of chemicals that cause allergic reactions like hayfever, sinusitis, asthma, skin rashes, gastrointestinal upsets or swelling in the face or throat. This is often an immediate and severe reaction and the culprit food would be identified in an allergy test.
   
   
2. The other type of response isn't as severe and can take anywhere from 1 hour to 3 days to show any signs. In this case the body releases antibodies called IgG. When an offending food enters the bloodstream, an IgG antibody 'tags' them. One or two of these 'tags' won't cause much of a reaction, but if a lot of the offending food is eaten, the buildup of IgG antibodies will cause symptoms. These symptoms include nausea, cramps, flatulence, sweating, skin rashes, migraines or depression. This kind of allergic reaction is more commonly termed an 'intolerance'.

The best way to work out whether you are intolerant of a certain food is to do an exclusion diet. This involves avoiding any 'suspect' foods (foods you think you may be reacting to) for a period of 15 days. Make a list of your suspect foods and try eliminating either one food type at a time, or all of them at the same time. You would also need to check food labels to ensure none of the foods on your list are some of the 'hidden' ingredients. Common suspect foods are:

Wheat, dairy, gluten grains (i.e. wheat, oats, barley and rye), citrus fruits, eggs, nuts, tea, coffee, chocolate and soya.

After the 15 day period, test by eating a pure source of the food you have eliminated e.g. if you are testing for wheat intolerance, eat a water biscuit and not bread. Follow the test as follows:

• Sit down for 5 minutes, to ensure your body is at rest, and take your resting pulse for sixty seconds.
  Record it.
• Eat more than usual of the food you are testing.
• Take your resting pulse again after 10, 30 and 60 minutes. Record these.
• Keep a record of any symptoms over the next 24 hours.

Foods that you show a IgG reaction (an intolerance) to should be avoided for 6 months. The immune cells that produce the IgG antibodies have a short-term 'memory', so after 6 months there is unlikely to be any residual 'memory' reaction to a food that's been avoided. When introducing an IgG sensitive food, try to eat it at most once every 4 days to reduce the chances of a buildup of allergen-antibodies and so lessens the chances of symptoms of intolerance.

References:
'Optimum Nutrition Before, During and After Pregnancy' by Patrick Holford and Susannah Lawson