Food Sensitivities: Why You Don’t Need an IgG Test
NUTRITION COACHING FROM YOUR REGISTERED DIETITIAN NUTRITIONIST Here IN BOSTON’S BACK BAY
If you’re experiencing tummy troubles - especially related to running or other endurance events - then you’re not alone. Since the priority is to oxygenate your muscles instead of your GI tract, symptoms like cramping, nausea, and diarrhea are unpleasant, but not uncommon.
Still - that doesn’t have to be your norm. And if symptoms seem to last a bit longer than you’d like and you feel that something isn’t quite right, I’m here to help you from getting lost on an expensive, dead-end road.
Is it a food sensitivity?
I often see athletes convinced that something is wrong. Namely: that they have a food sensitivity. The world is abuzz with concern for these and for the testing that claims to diagnose them. Unlike well-defined allergies and intolerances, food sensitivities have become scapegoats for everything.
The controversy here lies in the “diagnosis” - namely the IgG test that isn’t what it claims to be - and the subsequent food fears, elimination diets, and association with eating disorders that often follow a sensitivity diagnosis. Read on before you take out your wallet and empty your pantry.
One of these things is not like the other:
Allergy: An allergy is an immune response. If you have a peanut allergy, for example, your body recognizes peanut protein as a threat and launches an attack with Immunoglobulin E (IgE) antibodies. Allergic reactions range from hives to GI distress to anaphylaxis and can be life-threatening.
The oral challenge test is the gold standard for diagnosis, but allergists commonly use an IgE blood test or skin prick along with your personal history in order to make a diagnosis. Here, avoiding the allergen is key.
Intolerance: Food intolerances are digestive limitations. In the case of lactose intolerance, you’re lacking the necessary amount of lactase enzyme needed to fully digest lactose, which is the naturally-occurring sugar in milk. Your body doesn’t attack the lactose, but your body can’t digest it (or digest all of it). Digestive symptoms are usually gas, bloating, diarrhea, and general discomfort.
Unlike a milk protein allergy, which requires that you to avoid all dairy products, individuals have varying degrees of lactose tolerance - a certain load or threshold of digestibility. This is why you might be able to enjoy a cup of yogurt but run to the bathroom after a milkshake. And, because your body isn’t waging war with IgE antibodies, the lactose itself is not inherently harmful.
Sensitivity: Food sensitivities ::drumroll:: aren’t clearly defined. And though a Google search yields 2,990,000,000 results, the NIH’s PubMed.gov yields only 31 published papers on humans in the last 10 years. There’s a whole lot we don’t know, but research is looking closely at the microbiome, the central nervous system, and autoimmune diseases to understand why and how some bodies react to food in novel ways.
How can we test for something we don’t understand?
Many reputable companies have claimed this frontier by “diagnosing” food sensitivities with tests for Immunoglobulin G (IgG) memory antibodies. Here’s the key: These tests are accurate and valid, but they haven’t been interpreted correctly. Unlike IgE, IgG is a normal physiological response to repeated exposure. In this way, IgG antibodies actually indicate tolerance and desensitization!
See the problem? You’ll end up with a colorful printout of your IgG antibodies, which (not coincidentally) read like a menu of your habitual intake. This has created a storm of unnecessarily restrictive diets, decreased quality of life, and disordered patterns of eating.
The American Academy of Allergy and Asthma and Immunology (AAAAI), the Canadian Society of Allergy and Clinical Immunology (CSACI), and the European Academy of Allergy and Clinical Immunology (EAACI) have all warned against using IgG testing as a diagnostic tool. And, for the RDNs out there, the Academy of Nutrition and Dietetics has put out a call to action highlighting the need for standardization, reliability, and intervention protocol.
Where does this leave you?
If you’ve ruled out allergies but still feel terrible, all is not lost. While an RDN can’t diagnose you, we can track, evaluate, and manage your symptoms with food and lifestyle interventions. Here are actionable steps you can take:
Keep a food journal. Include meal timing, food amounts, training details, and timing of details of symptoms.
Bring your journal to a registered dietitian nutritionist (RDN) who uses food-forward interventions.
Ask questions, including about these tests. With the appropriate lens and the right team, symptom resolution is possible.
