Nutrition Q&A: Are food sensitivity tests legit?
There has been a bit too much going on over here to get a new post up this morning, but after seeing a recent Instagram post by fellow RD Abby Langer on food sensitivity tests (her posts are great!), thought I’d share something I wrote a while ago with a bit more detail on why food sensitivity tests are, at best, not useful. I hope this is helpful!
But first, what is a food sensitivity?
A food sensitivity is sort of just how it sounds - a food that just doesn’t seem to agree with you. That can manifest in various different ways, as I mentioned above. For example, every time I eat tomatoes I get awful acid reflux, and would consider myself to be “sensitive” to tomatoes and for the most part, avoid them. A food sensitivity is not a food allergy, which is an intense immune response your body has to even a small amount of a food (e.g., peanuts, shellfish, eggs) that it identifies as a danger. This response can be fatal when anaphylaxis occurs. Food sensitivities are also not food intolerances, which is when we have trouble digesting foods (e.g., lactose intolerance), nor are they celiac disease, which is an autoimmune condition. Food sensitivity tests do not test for allergies, intolerances or celiac disease.
How do these tests work?
Food sensitivity tests test for a specific antibody called immunoglobulin G, or IgG. The body’s immune system produces these antibodies when in contact with a foreign substance, like food, and it’s a completely normal response. In fact, the body has a more notable IgG reaction to foods that have been eaten frequently and the result is higher levels of IgG in the blood. Higher IgG levels also show foods that have been eaten recently or more sporadically. IgG levels are lower or not present for foods you don’t eat at all.
What does this mean?
IgG food sensitivity tests are simply reacting to the foods you may eat more frequently or have eaten lately. They’re not indicative of any kind of sensitivity, and there currently are no randomized controlled trials showing IgG values can be used as a tool for diagnosing food allergies, intolerances or sensitivities. In fact, newer research is showing higher IgG levels in relation to certain foods may indicate more of a tolerance to that food. Consider higher IgG levels a normal immune response to exposure to certain foods or food ingredients. The American Academy of Allergy, Asthma and Immunology is also vocal about the irrelevance of IgG of testing. Food sensitivity tests are also not regulated by the FDA, and just like dietary supplements, companies who make them can basically say whatever they want to say about the tests and results without anyone checking to see if they’re right or wrong.
My other problem with these tests
Aside from not being scientifically sound, my beef with food sensitivity tests is the harm they have the potential to cause. I’ve had folks come to me with a laundry list of foods they don’t think they’re “allowed” to eat anymore because of these tests. Not only are these some of their favorite foods (because remember, the tests show foods you eat often!), but now there’s an unnecessary layer of fear around them. Following a super restrictive diet after taking a food sensitivity test can also result in micronutrient deficiencies, a negative relationship with food, and disordered eating (if not already present!).
Ok, how do you test for a food sensitivity?
The gold standard for food sensitivity testing is an elimination diet. I am admittedly not the biggest fan of these because, if done right, they are so tedious and restrictive. If done incorrectly, they can also be tedious and restrictive, but also super confusing. It’s helpful to have the guidance of a dietitian if you think you’re sensitive to certain foods and want to try an elimination diet. I should note here that I haven’t had many clients or patients go through with elimination diets because during the nutrition counseling/coaching process we have found their issues to be more related to anxiety, stress and/or dietary restriction as opposed to one specific food.
Very helpful information, thank you!