Are Food Sensitivity Tests Accurate?

Are you considering a blood test to see if you have a food sensitivity? Surprised that your insurance company will not pay for the cost of the test? After all, it is a medical test. Well, maybe it really isn't.

Food sensitivity is not an official medical diagnosis. This term, however, is used by the makers of various blood tests claimed to detect sensitivities to certain foods. And, the evidence supporting the ability of these blood tests to assess problems with eating certain foods is questionable.

Allergy vs. Intolerance vs. Sensitivity

Food allergies happen when the immune system reacts to a substance, which is usually a protein, in a food or group of foods. Typically, the immune system goes into gear when it detects a harmful substance. It does that by making antibodies. When someone has a food allergy, their immune system identifies a specific protein as harmful and makes antibodies to fight it off. This results in a range of symptoms, including skin rashes and breathing problems.

Food intolerances are not an immune system reaction. They relate to trouble digesting foods. Food intolerances occur due to the lack of an enzyme needed to digest certain foods or, sometimes, as a reaction to additives or naturally occurring compounds in foods. Individuals with food intolerances may be able to eat small amounts of bothersome foods. But, when they have too much, their body reacts. For example, many people with a lactose intolerance find they can drink a small amount of milk with meals or eat yogurt or other foods that are lower in lactose without experiencing any symptoms.

Food sensitivity has no standard medical definition. It can be used to mean anything. Sometimes, this term is used instead of food intolerance, such as a sulfite sensitivity and histamine sensitivity. Other times, it is used as a catch phrase that includes both food allergies and intolerances.

If you think you might have a food allergy or intolerance, talk with your health care provider. Discuss your symptoms so that other possible conditions can be ruled out first. This is especially true for celiac disease, since it can result in damage to the small intestine. In some cases, people who experience symptoms similar to those of celiac, but test negative for it may be told they have non-celiac gluten sensitivity. Research is limited at this time and there is no specific test for it. Some of these individuals with NCGS may see improvements in symptoms such as abdominal pain, bloating, diarrhea, constipation and chronic fatigue when gluten containing foods are avoided. However, avoiding gluten does not seem to help everyone manage these symptoms, so other changes in the diet may be recommended.

What About Food Sensitivity Blood Tests?

While "food sensitivity" is not an official diagnosis, the popularity of food sensitivity blood tests has grown. However, at this time, the evidence is lacking to support the use of these tests in diagnosing adverse reactions to foods.

There are a variety of blood tests being offered that claim to test for food sensitivities. Similar to allergy testing, these tests typically look for immunoglobulin antibodies:

• In the case of food allergies, skin pricks and blood tests that measure a protein called immunoglobulin E, or IgE, are used to diagnose them. The presence of IgE antibodies generally indicate an immune system response.
• Food sensitivity tests typically look for the presence of IgG (not IgE). IgG antibodies have not been shown to reliably identify either food allergies or sensitivities. Most people produce IgG antibodies after eating food. They are not specific to a person's sensitivity, although past or frequent exposure to a food may cause these levels to be higher.

Because IgG blood tests have not been proven to identify food sensitivities or allergies, there is a lack of evidence to support making changes based on their findings. The restrictions suggested by IgG test results may lead you to unnecessarily avoid healthy foods. Or, they may prompt individuals with food allergies to include foods that could be harmful to them.

Professional organizations that specialize in the treatment of food allergies, do not recommend IgG testing due to the lack of evidence for this use. This is why insurance companies will not cover the costs of the tests.

Best Options at This Time

If you think that certain foods are causing health problems, what should you do?

• Make an appointment with your health care provider and explain your symptoms.
• Find out from your provider if you need a referral to an allergist for further testing.
• Ask your provider how you can learn more about food allergies and food intolerances.

Based on your results, ask for a referral to a registered dietitian nutritionist. An RDN can design an eating plan for you based on your diagnosis, health needs and food preferences.