The elimination diet is the “gold standard” for identifying food sensitivities, but data suggest that eliminating foods identified using IgG food allergy testing in certain conditions may result in significant symptom improvement.
The role of IgG-mediated reactions causing allergic symptoms continues to be debated. Some practitioners feel that Type 1 IgE-mediated reactions are the only “true” food allergies. IgG food allergy testing, or delayed hypersensitivity testing, remains controversial.
In theory, since IgG can trigger a powerful protective response to protect the body from what it perceives as a threat, it is possible that food-induced IgG will cause the release of inflammatory chemicals and cause health symptoms. But, we commonly have low levels of anti-food IgG in our bloodstreams and do not react to them. So, the presence of anti-food IgG, even at high levels, doesn't necessarily mean that the food is causing the reaction. It may even be that an increase in anti-food IgG might indicate a recovery of an IgE-mediated allergy and not that the body views the food as a threat.
IgG-mediated food allergy is complicated. However, data suggest that eliminating foods identified using IgG antibody food testing in certain conditions such as, irritable bowel syndrome (IBS) can result in significant symptom improvement.
There is no standardized IgG testing – different labs may produce different results. There can be false positives (the test indicates you are food sensitive, but you really aren’t) or false negatives (the test indicates you are not food sensitive, but you really are). If you’ve eliminated a food or food component from your diet, for example gluten, for months the test will indicate that you are not sensitive to gluten containing foods. This is only because you’ve removed it from your diet and the body is no longer reacting to it, but you still may really be sensitive to gluten.
Interpretation of the test is important when identifying food sensitivities, but there is limited standardization here also (both with labs and practitioners). As stated above, the mere presence of anti-food IgG doesn't mean that it is causing your symptoms. If IgG testing indicates a reaction to multiple foods in one food group or many foods overall it usually means your gut health is compromised (i.e. “leaky gut”) instead of food sensitivities. An elimination diet may well be indicated, but figuring out why you have “leaky gut” (the root cause of the problem) is critical.
What should you do? If available and practical, practitioners use IgG antibody blood testing to compare with other pieces of the clinical picture and to have some sort of starting point for an elimination diet based on likely food “allergy” candidates. Testing may help to confirm food sensitivity in the context of the full clinical picture. However, test results may result in you eliminating foods unnecessarily. None of the allergy tests alone (IgE or IgG antibody testing) are sufficiently accurate to identify the specific foods that are triggering symptoms.
The elimination diet and challenge is the gold standard for identifying IgE-mediated and IgG-mediated (delayed hypersensitivity) food sensitivities. A comprehensive elimination diet is very difficult and and testing may be useful to help give you a starting point for a modified elimination diet plan, especially if you have IBS.
**Remember that determining what kind of food sensitivities you have is only the first step in healing. You must also look into why your immune system is reacting to these foods which is key to determining the root cause of your symptoms or health condition.
This is general guide to IgG food allergy testing. Many different types of food sensitivity tests are currently on the market and a full review of those tests is beyond the scope of this page. Many practitioners report good success with different types of food sensitivity testing, but overall, this type of testing remains controversial. The clinical interpretation of the test results appears key to the usefulness of the test. Check out my references for more information.
The elimination diet and challenge is the “gold standard” for identifying food sensitivities. A comprehensive elimination diet is very difficult and if it doesn’t seem like something you can do and you are willing to pay out of pocket for testing, IgG food allergy testing (or other food sensitivity tests) may help you to identify foods that you may be sensitive to and ultimately assist in your healing process.
Some references: Joneja, JV Dealing with Food Allergies, 2003; Vickerstaff Health Services, Diagnosis of Food Allergy FAQ sheet 2007, http://www.allergynutrition.com/index.php; Mullin GE, Swift KM, Lipski L et al. Testing for food reactions: The good, the bad and the ugly. Nutrition in Clinical Practice 2010;25,192-8
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