Should I get a food sensitivity test? My clients, readers and audiences will frequently ask me. To which Ill answer that question with another question (yeah, its a Jewish thing ): what do you hope to get out of the test?

                Why do I ask this question? A couple of reasons:

  1. I cant give a straight answer.
  2. I want to see if the test that they want to get is indeed testing what they want to test.

And thats what well talk about in this newsletter the difference between food allergies, food sensitivities and food intolerances, as well as what they do and dont tell you.

Original source: here.

Food Allergies vs. Sensitivities vs. Intolerances

                These 3 terms are often used interchangeably, but they are different things. So lets give some definitions.

                Food allergies are the most well-known. Theyre severe and immediate. For instance, if you have a peanut allergy, within a matter of seconds of eating that peanut, your throat may shut. Or if you have a shellfish allergy, in a matter of minutes to hours, your skin breaks out in hives.

                Food sensitivities, by contrast are subtle and delayed. For instance, you eat gluten (found in wheat, rye and barley), and in a few days your joints are stiff. You drink milk, and the next morning, your nose is congested. Those are examples of sensitivities.

                Food intolerances are when your body doesnt have the enzymes necessary to process a certain food. For instance, with lactose intolerance, you dont have the enzyme (its called lactase) to break down lactose. Symptoms of food intolerance are usually restricted to just the digestive system, whereas the symptoms of food allergies and sensitivities are not limited to just digestion. They could be far ranging. The effects could be on your lungs, your joints, your skin, your brain, etc.

                The big difference between food allergies/sensitivities and food intolerances is that the former is an immune issue. The latter is purely a digestive issue.

Testing for Allergies vs. Sensitivities vs. Intolerances

                The testing for allergies and intolerances is pretty widely accepted by both the traditional medical community and the alternative medical community.

                Although testing for severe food allergies may not be necessary. After all, if you cant breathe after eating peanuts, do you need a test to tell you that youre allergic? Or does the absence of oxygen just kill your desire to have peanuts? The test is more for mild and moderate allergies.

                The most common test (though not the only test) for allergies is the skin prick test. Basically, a small amount of the suspected substance (pollen, food, etc.) is applied to the skin on the back of the arm. The skin on the arm is pricked with a lancet, and then you observe what happens to the skin. If it gets red, hot, bumpy and itchy, thats an allergy.

                Its a good test, but its not a perfect test, since there are false negatives (a false negative is when a test tells you that you dont have something when in fact you do). About 10-30% of results are false negatives (for food, that is. The false negative rate for things like pollen, mold, etc. is around 5%).

                The skin prick test is a gateway test for food allergies, as there are other ones if the results of the former are inconclusive.

                The test for food intolerances is a hydrogen breath test. Basically, you drink a beverage containing the suspected intolerance, and then you measure the amount of hydrogen that your body produces in response to it. If its more than a certain amount, youre likely intolerant to that food.

                Although its a good test, and very accepted, its not a perfect test (theres no perfect test). You can get false positives (a false positive is when the test says that you have something when you dont) when:

  • Youve recently taken antibiotics
  • You have a digestive disorder that affects the absorption of hydrogen
  • You have a condition called SIBO (small intestinal bacterial overgrowth)

Again, its a good test (the gold standard, in fact), but not a perfect test, and there are other tests for food intolerances.

Then we come to the highly controversial food sensitivity testing.

There are 4 possible immune reactions:

  • IgE: this is used to test for outright allergies
  • IgG: this is the most common test for food sensitivities
  • IgA and IgM: these are reactions to food sensitivities. Not many labs run them, but a few labs do.

The IgG test involves drawing the blood, and testing it for any number of different foods (usually 100, but some labs test for 50, others test for 250, etc.). It comes back with a result showing a bunch of different foods, with an evaluation of how sensitive you are to each one of them.

Its got all the elements to make it look scientific:

  • Needle goes into vein.
  • Blood comes out of vein.
  • Test comes back with lots of bar graphs.
  • Bar graphs have pretty colours.

But this is where the controversy begins. There are a bunch of arguments against IgG, IgA and IgM testing:

  • One study showed a false positive rate of 96%!!! In other words, 96% of the foods that it tells you youre sensitive to are not correct. Another study showed a 73% false positive rate. And a meta-analysis showed a 68% false positive rate. And there are others.
  • IgG, IgA and IgM may be elevated for other reasons besides food sensitivities, like infections, inflammation, etc.
  • There are reasons for sensitivities besides immune. Like psychological and environmental.
  • Theres no standardization. Different labs may test the same thing differently, and thus get different results.

So those are the arguments against. But if it was complete hogwash, there would be no benefit to these tests. And yet, there are benefits:

  • One study found that removing foods based on the results of an IgG test improved the symptoms in people with IBS (irritable bowel syndrome). Another study found the same thing.
  • One study showed a greater amount of IgG in people with major depressive disorder.
  • In one study, IgG, IgA and IgM were tested both in people with rheumatoid arthritis (RA), and those without RA. Those with RA showed much higher amounts of IgG, IgA and IgM, compared with those who didnt have RA.

Unfortunately as is often the case with research, the conclusion at this point in time in regards to IgG, IgA and IgM testing is more research is necessary. If there was absolutely no research showing the benefits of this kind of testing, you could say conclusively that theres nothing to those tests. But the fact that some preliminary research is showing some promise, it would mean that you cant totally throw out those tests yet.

So although right now, IgG, IgA and IgM testing for food sensitivities is used with great skepticism, there is one other test which has stood the test of time, and has great scientific validity. The low-tech elimination diet.

Its just like what it sounds. For a period of 2-4 weeks, you eliminate the most common food sensitivities, and after the elimination period, you start reintroducing them one-by-one every 3 days and noting symptoms. If you want the full details on how to do this diet, heres a great article.

There are pros and cons to the elimination diet (like I said, no test is perfect).

Pros:

  • Accuracy: theres no debate about symptoms. If you feel a symptom, you dont need a lab test to validate that.
  • Price: it costs nothing.

Cons:

  • Compliance. You have to be super strict about avoiding the offenders for the period of time that youre eliminating.
  • Time: unlike a lab test, where you learn the results in a few business days, elimination and reintroduction can take 4-8 weeks.
  • Youre making the assumption that the foods that you are eating youre not sensitive to them.

What You Dont Get from Food Sensitivity and Intolerance Testing

                As I keep saying throughout this article, theres no perfect test for anything. But even if there was, you should know what you are and what you arent getting.

                With food sensitivity testing, youre getting an immunological test (regardless of whether you use the elimination diet, IgG testing, or something else).

                With food intolerance testing, youre getting a digestive test.

                What youre not getting is a list of foods that are bad for you if you have no immunological or digestive issues with them.

                For instance, energy drinks are not good for people with high blood pressure. But they wont come up on immunological or digestive tests. Fruit juices, and pop are not good for diabetics, but they wont come up on immunological or digestive tests.

                So to clarify, food sensitivity and food intolerance tests will only tell you what not to eat only if your reaction to the foods is immunological or digestive. But if its anything outside of that (lets say its bad for your heart, or your brain, or your skin, or something else), they wont tell you.

                You have to use the right tool for the job. And to use the right tool, you have to know both what it does, as well as what it doesnt do.