Every year I get a handful of clients who ask if they should get a food intolerance test, or bring me results if they have already had a food sensitivity test. They want to do everything they can to give their body what it needs and avoid foods that could be potentially problematic. I scan the stoplight color coded sheet: red- do not eat these foods, you are clearly sensitive to them; yellow- these foods may be problematic; or green- eat these foods without concern. Clients are so confused and concerned, “I eat these foods all the time!” they say gesturing to the red column, indicating foods like chicken and rice. “What am I supposed to do?” I understand. their confusion and fear, so let’s clarify things and get to the bottom of food sensitivity testing.

Food sensitivity vs allergy

There is a big difference between a sensitivity and an allergy. The actual incidence rates of medically diagnosed food allergies remains stable at 2-3% of the population, however the prevalence of adults who think they have a food allergy has climbed to 25%. That means one in four adults think they have an allergy (hint, they don’t). Most of these so-called allergies are self-diagnosed and have not obtained a medical diagnosis.

A food allergy requires a reaction mediated by the immune system.They also are not dose dependent, you can get a reaction from a trace amount of the food such as crumbs.

A food intolerance means there is a reaction that is not mediated by the immune system.It is dose dependent, you can likely have a little bit without getting symptoms.

What does a food intolerance test tell you?

A food intolerance test refers to blood tests for an antibody. One of the most common forms of food intolerance testing is a blood test to measure immunoglobulin G (IgG) antibodies. Ooo blood test and big fancy words, that sounds legitimate. These blood tests purport to diagnose “food sensitivities” that allegedly manifest as everything from acne to joint pain.IgG is the most abundant antibody and consists up to 75% of total circulating antibodies and has a high circulation in the body. Elevated IgG reflects exposure to a compound. IgG have a long half-life of up to 96 days.

The issue with food sensitivity testing

First, there is no standardized methodology for IgG testing. This is a huge red flag. Different labs will likely yield different results, there’s no quality controls. Not a single study published on the purposed utility of IgG testing has published any details regarding validation of the assay in humans.

Here’s the issue many practitioners fail to realize or mention- IgG antibodies in the blood don’t mean you have a food intolerance. In fact, it’s quite the contrary. Pretty much anyone who has IgG antibodies to many different foods. Moreover, these antibodies have been linked specifically to the development tolerance or desensitization. If your blood contains IgG antibodies to a vast array of foods, it means your body’s been exposed to them and it’s totally cool with them.

Tolerance to food is acquired through immune cells called iTreg cells. iTreg cells go the the intestinal lining where they suppress allergic responses to food allergens (the suppression of IgE) and create IgG. therefore, an elevated IgG does not reflect an intolerance to food, but the exact opposite- it is associated with immune tolerance.

The down sides to testing

There’s actually a few down sides to getting these tests. For one, they’re usually expensive. Do yourself a favor and save your money; or treat yo self to a massage, new shirt, or whatever else jingles your bell, but don’t waste it on a food sensitivity test.

They also freak people out, and rightfully so. No one wants to be handed a list of forbidden foods (many of which they likely recently ate and enjoy). I can’t image the stress of seeing some of your favorite and commonly eaten foods thinking you can’t have them anymore.

By eliminating foods from your diet you can actually increase the likelihood of developing a food intolerance. Research is quite clear that eating a wide variety of food is best for health; it improves gut microbiome health and longevity. Therefore unnecessarily cutting out foods can decrease gut microbiome diversity (we don’t want to do that) and make you miss out nutrient-rich foods that contribute to overall vitamin and mineral status in the body.

An alternative to food sensitivity testing

If you suspect you don’t tolerate a food well, keep a food log for a few days. Write down what you eat and any symptoms that come up. For example, 12:30 turkey burger with ketchup, onion, pickles and sweet potato fries. 2:00 feeling bloated. At this point we don’t know what’s causing the bloating, but after several days (or weeks depending on how long you log your food & symptoms) you can start to see patterns and identify potentially problematic foods.

Once you think you’ve identified the culprit, eliminate that food for two weeks. Do you still have symptoms? Then it wasn’t that food. If symptoms are gone, after two weeks reintroduce it and see if symptoms return. You don’t need a medical diagnosis to know what foods do/don’t feel good when you eat them.

Takeaway

Elevated IgG does not reflect intolerance to a food, but rather an exposure to the food. Hence, a test result of elevated IgG can simply mean you’ve eaten that food. IgG elevation is associated with immune tolerance, not intolerance. If you think you have an intolerance, keep a food log with symptoms and try to identify the culprit. Eliminate that food for two weeks and then reintroduce it.

About Dr. A’nna

Dr. A’nna Roby is on a mission to help athletes better understand and fuel their bodies so. they can achieve their personal best. As the only combined PhD/Registered Dietitian in the world with all Ivy League degrees specializing in sports performance nutrition, Dr. A’nna works with athletes, scientists, innovators, and coaches to help progress the field of sports science. She is the Chief Research Officer of Athlete Blood Test and enjoys working with clients through her private practice. You can reach her at anna@drannaroby.com.