By Jenna Corbin, MS, RD, LD, CSSD, CLT, PES, CESThe food we eat is supposed to nourish our bodies and make us feel content and energized. Why is it that food sometimes causes pain, fatigue, nausea or worse? Whether it’s due to increased awareness, more processing of food or a changing food environment, it seems more people are being impacted by food-related reactions, sometimes known as allergies and intolerances. Despite common misconception and misuse, food allergies and food intolerances are not the same thing. In addition, to make the party a little more exciting, we have “food sensitivities” to join in on the fun. Although there’s a lack of consensus about the definition of food allergies, sensitivities and intolerances (and the confusing overlap and interchangeability in the literature), in general, the biggest difference is whether the immune system is involved or not.
Food Allergy vs. Sensitivity vs. IntoleranceA food allergy is a very specific immune-mediated adverse reaction involving IgE antibodies, where the body mistakes a particular food as a harmful substance. It’s generally a quick reaction and mostly involves the skin, airways, and gastrointestinal tract--so think hives, rashes, asthma, swelling of the airway and even vomiting. Anaphylactic shock, serious breathing issues and loss of consciousness are some of the most serious consequences, as these can ultimately be fatal. The eight most common allergens are milk, eggs, fish, shellfish, tree nuts, peanuts, wheat, and soy.Food sensitivities are also immune-mediated, but are highly complex, non-allergic (non-IgE), non-celiac inflammatory reactions generally caused by the breakdown of oral tolerance mechanisms. (Note: Celiac disease is neither an allergy, sensitivity, nor intolerance, but rather an autoimmune disease, thus, will not be discussed further).Unlike food allergies, food sensitivities can follow multiple inflammatory pathways, therefore are quite complex from their effects on the body to identifying trigger foods. Symptoms may be delayed by hours or days; reactions may be dose-dependent and there are many, many potential reactive foods/food chemicals—even so-called “anti-inflammatory” foods (e.g., fruits & vegetables, spices, fish, any “healthy” food). Effects on the body can range from IBS and GERD to migraines, fibromyalgia, arthritis and more.Intolerance is a non-immune reaction that is most commonly a functional issue within the body; a “mechanical” problem or failure. For example, the inability to properly break down food due to the lack of an enzyme, similar to lactose intolerance. Lactose intolerance is a result of the small intestines not making enough of the enzyme lactase to breakdown lactose. Gastrointestinal symptoms are the usual result (e.g., nausea, gas/bloating, stomach pain, bowel pattern changes/diarrhea). Malabsorption (fructose malabsorption), irritants (parasites, bacterial overgrowth), toxic reactions (food poisoning) and pharmacological factors can all cause non-immune reactions resulting in food intolerance-type symptoms. So determining the root-cause is key to addressing the issue. Adding enzymes, reducing the amount of exposure and avoidance are possible considerations depending on the cause.
Immune System & Adverse Food-Related ReactionsThe immune system is like a very complex and effective “combative” squad. Its “soldiers”, or white blood cells (WBCs), house chemical “weapons” waiting to attack/destroy “invaders” (i.e., food antigens). The stored chemical weapons within the WBCs that are released upon invasion are called mediators, of which there are about 100 (e.g., histamines, leukotrienes, prostaglandins, cytokines). Mechanisms (antibodies such as IgG, IgA, IgM; complements such as C3 and C4; T-Cells; phagocytes) are what trigger mediator release from the WBCs. The release of these mediators is what causes the negative effects and symptoms.In the case of a food allergy, once the immune system decides an ingested food is ‘bad’ (e.g., egg) it produces IgE antibodies (the mechanism). These IgE antibodies find their way to the WBCs (mast cells) where the chemical weapons (mediators--about 20 possibilities) that cause the symptoms (e.g., skin, airway, GI tract) are released.For food sensitivities, once the immune system decides a food is ‘bad’ (e.g., parsley, tomato, blueberry, etc.), many things can happen depending on:
- which mechanisms trigger mediator release (IgG, IgA, IgM; Complements C3, C4; T-Cells; Phagocytes),
- which WBCs are involved (Lymphocytes, eosinophils, neutrophils, basophils, monocytes, and
- how much food was ingested since the reaction may be dose-dependent.