Blood tests for food intolerances are becoming increasingly popular. The tests promise to deliver personalized recommendations for diet and supplements in order to optimize health. It’s an appealing pitch but the science, unfortunately, does not back it up.
Usually (though not always) food allergies occur when there is a reaction between the protein component of a food and molecules in our body known as IgE. In contrast, food sensitivity testing measures a molecule known as IgG. The tests claim that a person’s IgG response to various foods indicates their level of sensitivity. In fact, it’s perfectly normal for an IgG response to occur after eating. Because of this, an IgG response on a test is more indicative of a person’s prior exposure to a particular food product than it is of a sensitivity or allergy. The more frequently you eat a food, the stronger your IgG response, and the more likely it is to be flagged on a food sensitivity test.
That’s not to say that food allergies, intolerances and sensitivities don’t exist - they do. But rather than spending money on a dubious blood test, most would be better off getting assessed by an allergist or registered dietitian. Unfortunately, food sensitivity testing most often results in false positives and can lead people unnecessarily restrict their diet.