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Mary E. Pritchard Ph.D.

Is it Food Allergy, Food Intolerance, or Restrictive Eating?

What's the difference anyway?

“One man’s meat is another man’s poison.” - Titus Lucretius Carus

My dietician and I recently came to a standstill.

A few months ago she asked me, “How many of your food issues are psychosomatic?”

“I don’t know,” I responded truthfully. “A few years ago my bloodwork showed allergies to dairy, egg, sugar, and some other random things. My earlier bloodwork showed sensitivity to gluten.”

“I’m not so convinced,” she replied. She challenged me to incorporate those foods back into my diet and see what happened.

I did, and the same thing that happened before when I ate those foods happened again – digestive upset when I ate gluten, eggs, and dairy; a rash when I ate sugar.

That’s when we came to a standstill and she sent me to an allergy clinic.

As it turns out, food allergies aren’t as simple as we once thought, and they’re becoming even more controversial. An allergy is the immune system’s overreaction to a normally harmless substance. In people who are predisposed to food allergy, the immune system creates an antibody called immunoglobulin E (IgE) when it is first exposed to the offending food, or allergen. When the allergen reappears, IgE signals cells to release chemicals, including histamines (which stimulate nerves and dilate blood vessels) and leukotrienes (which contribute to inflammation). Symptoms occur immediately upon ingestion of the food and, depending on the severity of the allergy, may include lightheadedness; itching, hives, or rash; swelling of the lips, tongue, and throat; nausea, vomiting, cramping and diarrhea. Rarely, a food allergy will trigger a life-threatening, whole-body reaction known as anaphylaxis, in which airways constrict and blood pressure drops precipitously, causing shock, loss of consciousness, and sometimes death. People with food allergies must avoid the dietary culprit, but in case of accidental exposure, a self-injecting device (EpiPen, Twinject) can supply enough epinephrine to dampen the reaction until medical help arrives. Common food allergens include: milk, eggs, peanuts, tree nuts, fish, shellfish, wheat, or soy.

But what if you don’t have an allergic reaction immediately to the food, yet you bloat half an hour after eating it? That might be food intolerance. As early as the mid-1900s, physicians observed that the foods which produced immunoglobulin G (IgG) reactions were usually the same foods that their patients reported craving – for as long as 72 hours after initial consumption. Fast forward to the 21st century and doctors and scientists are still asking the same question. But Dr. Jonathan Brostoff has a theory. According to Brostoff, when we have a mild immune reaction to a substance like food, it almost acts like an endorphin (e.g., runner’s high) in our bodies – with one big difference. The immediate sense of reward caused by eating the offending food is following by a physiological sense of lack, thereby increasing the craving for the food that we are actually intolerant of. But because food sensitivities are often delayed, we never connect it to the food we are craving. Weird, huh?

So what is a food intolerance? Food intolerance/sensitivity is also an immune reaction – this time to the immunoglobulin G (IgG) antibody – and usually results from the inability to digest or metabolize a food completely. The symptoms—gas, bloating, nausea, and diarrhea— are typically delayed and may occur up to 48 hours after ingesting the food. Symptoms of food intolerance overlap those of irritable bowel syndrome (IBS), and food intolerance can trigger episodes of IBS. Common food intolerances include: gluten, dairy, alcohol, aged cheeses, cured meats, yeast products, spinach, and tomatoes.

But here’s where it gets tricky. While IgE allergies are easy to detect with skin pricks (you don’t usually even need to be tested as the allergic reactions are immediate and sometimes life threatening), the accuracy of IgG tests are hotly debated. While most doctors recognize that food intolerances are a real phenomenon, they disagree about whether you can accurately test for them using saliva or blood.

But if there’s no accurate way of testing IgG responses, how do you know if you have a food intolerance? A food elimination diet is a method of identifying foods that an individual cannot consume without adverse effects (e.g., gas, bloating, nausea, and diarrhea, IBS). Elimination diets typically involve entirely removing a suspected food from the diet for a period of time from two weeks to two months, and waiting to determine whether symptoms resolve during that time period. There are a variety of books and websites out there that walk you through this step-by-step.

And this is where I stand right now. At 41, it’s pretty clear that I do not have an IgE reaction to any food. However, food intolerances are still a real probability. The allergy doctor put me on a FODMAPs elimination diet to see if that would help with my digestive symptoms.… Depending on how that goes, she may send me in to a Gastroenterologist, who will biopsy my colon and check for IBS.

Bottom line: Do you have a food allergy (IgE)? If you do, you probably already know it. Having if you experience digestive symptoms when you eat certain foods, it might be an IgG response. Back to my dietician’s question: “How many of your food issues are psychosomatic?” I think the assumption is that if I do well on the FODMAPs diet, then my intolerances are “real.” However, a biopsy may be the only definitive answer – and that’s an experience I am not looking forward to.

I hope you found this helpful. Do you have any suspected food intolerances? I’d love to hear about them in the comments below.

About the Author

Mary E. Pritchard, Ph.D., is a professor in the Department of Psychology at Boise State University.