Friend Don’t Let Friends Do IgG Testing

ID-10044134Are you like me? Did some well-meaning practitioner at some point recommend IgG testing as a means to find out if you have food sensitivities? Maybe you had nagging digestive issues, body aches, fatigue, or unexplained migraines. A blood test, they said, could help us see what foods your body doesn’t work well with. Not knowing any better and desperate to get better, you fork over the money. A lot of it.

And are you also like me in that when you got the results back and took out those foods … nothing happened. Ok, maybe you felt a little more energetic by cutting out wheat or in my case, had significantly less skin inflammation by cutting out dairy, but nothing else resolved. Over time you resumed eating anything you wanted and were the same as before, minus a couple hundred bucks. So what gives?

For many years now IgG testing has gone mainstream and has especially become prevalent with many naturopaths and integrative health care practitioners. When food sensitivities are suspected, many turn to these tests without much knowledge as to how they work or their limitations.

So what is IgG testing? It’s a blood test that measures the level of IgG present in the blood in response to different types of foods. The more IgG, the more reactive your immune system is to that food, or so the theory goes.

The main problem with this? Well, IgG is not the only antibody involved in food-immune reactions. By measuring IgG, we are only capturing a piece of the immune puzzle. So even if IgG tests were accurate, we would be missing large part of the picture.

That brings me to accuracy. As I alluded to, unfortunately IgG tests are just not all that accurate. They may on occasion capture true food sensitivity reactions, but the other interesting thing is that they may be showing you foods that you have developed a good tolerance to. Tolerance you say? Isn’t that exactly the opposite of what we are testing for? Indeed. Research has shown that in many cases those with high IgG responses to certain foods are actually showing a strong tolerance for that food. It’s almost a protective mechanism, of sorts.

Now, I am certainly not the first to raise questions about the validity of these IgG tests. In fact, faculty from my own Alma Mater, Bastyr University (where I first got my IgG test done, mind you) has even written on the topic ( In their article they discuss the reliability and validity of IgG tests. They submitted multiple samples from the same person to several different labs that offer IgG tests. They found that 2 of the 3 labs had results that were different enough amongst the samples to be unreliable. There were too many variations in IgG levels for the same food with the same blood specimen to yield any clinically significant result. Surprising, isn’t it?

The next consideration is validity. What basis or standard are we using to judge whether a particular IgG level is correlated with signs and symptoms of food sensitivity? Unfortunately, no standard has been determined. What one lab may deem as a high IgG level might only be moderate to another. Each lab can determine their own standard and make clinical judgments accordingly.

The last area of concern raised by the author of this article pertains to the use of therapeutic diets that correspond with the results. Often these tests come with suggested diet plans that propose elimination and rotation diets. As we have seen previously, clearly these are based on questionable results. Also they rarely take into account “untested” foods, so there is more guesswork in terms of what foods should and should not be included in the diet. This is just one more way in which IgG tests will very likely waste a lot of your time and money.

So don’t be like me. Don’t let you or someone you know waste their money on expensive food sensitivity testing that yields questionable results at best. All those colorful graphs should go straight into the recycle bin if you ask me. Unfortunately many practitioners see it as an easy way to show or prove to their patients on paper that they need to change their diet. There are much better ways, friends.

Mediator Release Test by Oxford Biomedical is by far the best blood test out there. You can read more about that on my web site and why I recommend it exclusively. If your practitioner isn’t aware of it, tell them to check it out or simply contact me for more information.

Like I said, friends don’t let friends do IgG tests. That’s why I’m telling you.

Stay tuned for my next post on the pros and cons of elimination diets!

Image courtesy of Ambro /

About Danielle VenHuizen

Registered Dietitian, Certified LEAP Therapist