25 October 2016Sorting out adverse reactions to foods

Ever experienced this situation? You’re having lunch with a friend, and the entire meal turns into a long tale of woe about your friend’s food sensitivities. The conversation is hijacked by complaints about “brain fog” or “bloating” or irritable bowel, or headaches or a collection of other symptoms that could have dozens of other causes. But your friend has decided the problem is food sensitivities. It’s increasingly common blame food for multiple problems. Is there any truth to this? And what exactly is a food sensitivity?

Adverse reactions to foods come in many forms

Food Allergy

According to the Food Allergy Research & Education true food allergies affect about 15 million Americans, close to 5% of the population. An allergic reaction is an immune response to a protein in a food. An immune molecule called IgE is released after exposure to the allergenic food protein. IgE attaches to cells that release histamine, which sets off the allergic reaction.

Severe anaphylactic reactions to food can be dangerous. Symptoms can start as soon as you are exposed to the food such as :

  • swelling of lips and face
  • swelling and tightening in the throat
  • breathing difficulty
  • drop in blood pressure and faintness

This type of reaction can be deadly and should be treated immediately. Common trigger foods include peanut, eggs, tree nuts and some fish. Food allergy can cause other reactions that aren’t necessarily dangerous, but are painful or annoying. Hives, skin rashes, nasal congestion, itchy mouth and asthma could be caused by food allergy. Again, these typically occur shortly after exposure to the offending food.

Food Intolerance

A food intolerance may be genetic or acquired. It may mean you cannot digest or absorb the food, or a component of the food. Lactose intolerance is one well-known example: if gut cells stop producing the enzyme lactase, the milk sugar lactose cannot be digested and absorbed. Instead, gut bacteria break it apart, leading to gas, diarrhea and discomfort.

Lactose intolerance can develop with age, or it can occur after a disease, such as ulcerative colitis. Avoidance of lactose-containing foods – milk, yogurt, ice cream -- solves the problem.

Strictly speaking, celiac disease is a genetic autoimmune disease, not a food allergy. When a person with celiac disease consumes gluten, their body launches an immune response, resulting in damage to the cells in their small intestine, diarrhea, malabsorption, and a host of other symptoms. The solution is complete avoidance of gluten-containing foods. Gluten is a protein found in foods made with any form of wheat, barley, or rye.

Food Sensitivity

Now we’re getting into a very murky area. Food is being blamed for a host of symptoms that can have many other possible causes. Headache? Could be dehydration. Could be stress. Could be poor posture. Could be a tumor or a blood pressure problem. Fatigue? Poor sleep habits, stress, an uncomfortable mattress, a generally poor diet, excess caffeine, alcohol could all contribute to that. Self-diagnosing with a food sensitivity may delay appropriate care.

Nevertheless plenty of people decide their symptoms are caused by food sensitivities. But which food? There is no standard way to diagnose any so-called food “sensitivity”. Even food allergy testing is prone to inaccuracies. If you know you have severe anaphylactic reactions to a certain food, a skin or blood test may confirm your allergy, but it is not going to give you any more useful information.

If you have hives or asthma or a rash, traditional allergy testing might provide information to use as a starting point for further investigation. You might show a reaction to milk, wheat, corn and soy on testing. This does not necessarily mean the food causes you any problems. You’d be advised to spend a couple of weeks avoiding all those foods, to see if your symptoms clear up. If they do, you add back one food for a few days and see if symptoms return. If you’re lucky, you identify which food causes symptoms.

I use the word “lucky” because it’s equally likely that your 2 week elimination diet won’t improve your symptoms at all. Or that adding foods back after the elimination diet doesn’t cause symptoms to return. You’re now symptom-free, but you don’t know why.

There’s another even more confusing possibility: you don’t react to any foods. Now what? In fact you may truly have an allergy, but traditional testing didn’t pick it up. The only way to identify offending foods is to keep a food/symptom diary and see if you can make any connections. Your allergist might also have some clues based on past experience, depending on your symptoms.

Identifying common food intolerances is comparatively simple. There are tests and diagnostic procedures for problems like lactose intolerance and celiac disease. Avoidance of the offending food quickly resolves the problem. But food sensitivity testing is another matter. Several years ago, Cytotoxic Testing was a popular way to supposedly diagnose sensitivities, but it was proved to be unreliable. It’s rarely seen anymore thanks to government regulatory actions.

The current variation on food sensitivity testing is the Mediator Release Test. Sounds pretty sciency, right? Even better, it involves blood. The premise: food sensitivities cause immune reactions that lead to a host of symptoms. The procedure: you send a blood sample to a special lab, where your blood is exposed to special food extracts; a machine takes measurements that supposedly mimic the immune response to that food in your body. Clients typically receive a long list of foods that supposedly caused immune reactions. The promise is that if you avoid all these foods your symptoms will resolve.

The idea that dropping food extracts (or whatever) into a vial of blood in any way mimics how your body digests and handles food always puzzled me. When you eat food, little droplets of food don’t enter your blood and interact with cells. The food is digested and broken down into component parts before it gets anywhere near your blood. So again, I was always puzzled about this test.

Professional medical and health organizations are also skeptical. Recently the Academy of Nutrition and Dietetics Commission on Dietetic Registration decided to discontinue professional education credit for courses for the MRT test, saying there “are no evidence-based guidelines” for MRT testing and “… current evidence does not support the use of mediator release assay test for diagnosing a food allergy”.

This doesn’t stop people from using the test, and believing in the results. If you have unpleasant symptoms and someone tells you you’re sensitive to 25 foods, and avoiding those will solve your bloating/headache/fatigue/brain fog, then in the absence of a serious medical condition, you might feel better. Placebo effect? It’s possible.

Here’s another possibility. Your pre-test diet was not the best. So when you change your whole diet to avoid these supposedly sensitive foods, your diet improves. You might end up eating more vegetables and fruit by default, or eating much less junk food or processed high sodium/high sugar foods, again by default. You feel better because your overall diet is better. You might even lose weight because you’re eating fewer calories. No more junky snacks or sugary lattes. Was it sensitivities or just a better diet? What is the takeaway message here?

True food allergies do cause a variety of dangerous and/or unpleasant symptoms. They can be hard to diagnose. Working with a qualified allergist is the best plan. If you are allergic, you will have to avoid those foods indefinitely.

Food intolerances can be diagnosed with tests, or you may suspect something, such as lactose intolerance, because your symptoms coincide with consumption of that food. Again, avoidance of the food is key, although for lactose intolerance you can take Lactaid®, which is the lactase enzyme in pill form, to ease symptoms.

There are no reliable evidence-based standard diagnostic procedures for food sensitivity. The long list of symptoms attributed to that could also be caused by other medical conditions. You might decide to avoid one or more foods because you suspect they’re causing problems. You may feel better, but is it the food or a placebo effect? Or did your diet improve by default? If better diet is the answer, you can do that without avoiding numerous foods. Unless it helps to believe you’re “sensitive” to soft drinks, candy bars, potato chips, French fries, cookies and cake.

Donna P Feldman MS RDN

is author of "Feed Your Vegetarian Teen", writes about food and nutrition at Radio Nutrition and is co-host of the Walk Talk Nutrition podcast series.

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