Beware of IgG test for food intolerance: scaremongering and rip-offs

IgG tests are booming. New products surrounding food intolerance are constantly appearing on the market. For people with a food intolerance, their quality of life is often limited by symptoms that include flatulence, diarrhea, abdominal pain, headache, skin problems, and fatigue, and they can often find no satisfactory causes for the symptoms.

Dubious providers take advantage of the despair of those affected and offer an apparently simple but expensive solution. With just a few drops of blood that you take at home, they promise to be able to recognize intolerance to hundreds of foods. Tests at home—especially the so-called IgG test—should be used with great caution because the IgG test is not suitable for diagnosing food intolerance.

"Experts and doctors agree: the IgG test is not suitable for diagnosing food intolerance!"
– Prof. Stefan Lüth, MD, Clinic Director, Chief Physician and Medical Director of the Clinic for Gastroenterology, Diabetology and Hepatology at the Brandenburg City Hospital.

What does the IgG test examine?

The IgG test examines whether there are certain antibodies in one’s blood. Experts call these antibodies immunoglobulins (Ig). Immunoglobulin G (IgG) is a special form of these antibodies. The immune system forms antibodies to differentiate between harmful and harmless substances.

The formation of IgG antibodies is a completely natural process in our body. IgG antibodies are raised against almost all foods that repeatedly come into contact with our intestines. For this reason, there are a lot of IgG antibodies in the blood of both sick and healthy people.

“Patients come to us every day who have significantly restricted their diet based on IgG tests and who are hundreds of dollars poorer at the same time. Often, patients hardly dare to eat anything anymore and accordingly eat much too one-sidedly. In the treatment it turns out that many of the omitted foods are very well tolerated.”** **

• André Sommer, medical doctor and founder of Cara Care.

How does the IgG test work?

The IgG test examines a form of antibody called immunoglobulin G. Sometimes a sub-form of it, IgG₄, is examined. The test manufacturers assert that the IgG test can determine food intolerances, arguing that the test detects certain forms of IgG antibodies that are directed against food. This is supposed to be a pathological reaction of the immune system that leads to the occurrence of food intolerance.

Is the IgG test reliable?

Many vendors advertise their IgG tests as the way to "quickly and safely" learn which foods you can tolerate and which you can't. It’s a promise that is tempting and that motivates many patients to order the expensive tests.

Doctors have been criticizing the reliability of the IgG tests for years. And studies show: often the results are purely coincidental and give no information about whether there is actually an intolerance.

_ “The promises from the providers are too good to be true. Patients should ask themselves why health insurance companies do not subsidize a cent for the test and instead pay for much more expensive medical diagnostics and certified nutritional advice.”_ – André Sommer

Why do doctors criticize the IgG test?

Doctors and other experts strongly doubt the validity of the IgG tests. They consider the tests to be unsuitable for determining food intolerance securely. To understand the criticism, it is important to know the basics of the intolerance.

What types of food intolerance are there?

Medical professionals distinguish two types of intolerance:

1. Immunological-based (allergic) intolerance, and
2. Non-immunological-based (non-allergic) intolerance.

With immunological intolerance, another antibody, immunoglobulin E (IgE), plays the crucial role. It mediates the allergic reaction to a food and can be safely detected in the blood. Therefore, an IgE allergy test is carried out by many allergists to detect a food allergy, which is very rare.

Non-immunological intolerance however, is more difficult to determine because IgE does not occur to a greater degree. Doctors and nutritionists therefore rely on a combination of a careful medical history, food diary, nutritional dieting, and provocation tests.

IgG tests promise to accurately detect these non-immunological intolerances.

Can the IgG test detect non-allergic intolerances?

No. The IgG test detects antibodies to food components. The manufacturers of the tests claim that the presence of these antibodies ensures the presence of an intolerance to the corresponding food component. This could be, for example rye, egg, corn, or wheat.

Leading allergy researchers agree: There is no evidence that the presence of IgG antibodies to food components alone proves an intolerance. The production of IgG against components of the ingested food is a natural reaction of the immune system. It is considered part of the natural protective function of the body. And in the vast majority of cases, there is no intolerance against a certain food, even if there is IgG in the blood.

What does this mean for food testing?

For patients this means: Beware of IgG tests from the Internet: The tests are mostly expensive and cannot deliver what they promise. A provider who advertises that their IgG test is "safe and reliable" ignores the results of scientific studies and petitions of many allergy associations and deceives patients with this statement. The associations are clearly opposed to the use of the IgG tests.

_ “Simply put, an IgG test just measures what you've eaten in the past few days. It has very little to do with intolerances.”_ – André Sommer.

Patients often change their diet in response to the test. In some cases this even improves the symptoms. However, this is not because the IgG test actually identified an incompatible food. Rather, such supposedly positive results come about through the great arbitrariness of the tests and a placebo effect.

Take, for example, an IgG test that shows an intolerance to wheat, rye, egg, milk products, corn, and barley. If a patient omits all of these nutritional components as part of an elimination diet, it may well be that the symptoms improve. Because some of these foods are among the most common causes of intolerance.

However, the patient will never know which food was actually the cause of the symptoms. Rather, she will limit her diet and continue to skip all of these foods. Although in fact it is possible that only one or none of the foods were the cause of the symptoms.

Scientists complain that the tests result in great arbitrariness. Patients forego many foods that they actually tolerate well. This can lead to a pronounced vitamin and mineral deficiency and malnutrition.

The high cost of the tests is also a factor. In conjunction with the low informative value, they are the reason why IgG tests are regarded by many experts as “rip-offs.”

Conclusion IgG tests are currently very popular and are a million dollar business. But leading allergy researchers agree: The tests do not allow for a reliable conclusion to be drawn. They are expensive and arbitrary and do not replace thorough diagnostics. The following therefore applies to patients: Don't be fooled by advertising promises and exercise caution when doing IgG tests at home. Food intolerance cannot be diagnosed with simple IgG tests for home use. The intolerance has to be diagnosed in stages and usually over several weeks. The cornerstone here is food diaries, elimination diets as part of nutritional advice and extensive medical diagnostics, which are effective and scientifically validated methods. Make no mistake: A food allergy can only be detected with an IgE test by an allergist.