When Should Food IgG Antibody Testing Be Considered?
The Adverse Food Reaction Test is useful for people who suspect that a food is responsible for causing their symptoms, but cannot identify which foods. The presence of circulating antibodies can affect each patient differently. Circulating food IgG antibodies are not diagnostic of a specific condition, but indicate an immune response to that food. The immune response could be a normal response that would not necessarily cause symptoms. Therefore, test results should always be considered in the context of the overall clinical picture. The role of IgG dietary antibody tests is still being investigated; however, studies have shown the benefit of testing under certain conditions.
Conditions associated with IgG food sensitivity
- Irritable bowel syndrome (IBS)
- Major depressive disorder
- Migraine headaches
- Skin rashes such as eczema
- Joint pain
- Autoimmune disease
- Crohn’s disease
The “leaky gut” connection
The presence of circulating IgG antibodies to food may suggest increased intestinal permeability, also known as “leaky gut syndrome.” When the tight junctions that form the barrier in the intestine don’t work properly, larger substances can “leak out,” triggering an immune response. This immune response can result in the production of IgG antibodies to food. There are multiple dietary and lifestyle factors that contribute to increased intestinal permeability. These factors include alcohol, stress, chronic use of NSAIDs, the Western diet (high consumption of red meat, animal fats, foods high in sugar and low in fibre), and prolonged and strenuous exercise.
What advantage does the IgG antibody test offer over other diagnoses?
IgG antibodies against food can cause a delayed response to food. While IgE antibodies can cause immediate hypersensitivity to a substance. It is generally easier for patients and clinicians to identify a food that elicits an immediate response. A late response to food can be more difficult to determine, and testing can be helpful. The IgG food antibody test assesses total IgG (1-4) compared to the single IgG4 test. This offers a more comprehensive evaluation; however, IgG4 tests are available to clinicians interested in that specific component of IgG.
The body of scientific evidence continues to develop regarding correlation with clinical symptoms and conditions for IgG testing (see conditions above). Furthermore, a study comparing methodologies showed that “the IgG ELISA test is more reliable and consistent than the cell size test in identifying food sensitivity.” ) and lymphocyte response assays.
Other types of adverse reactions to food that are not mediated by the immune system are called food intolerances. Food intolerances include lactose intolerance due to deficiency of the enzyme lactase in the intestine; tests are available for suspected lactose intolerance. Testing is not available for all food intolerances. These include vasoactive amines such as histamine and tyramine, food additives and preservatives (nitrites, sulfites, MSG, aspartame), salicylates, nightshades, lectins, FODMAPs, oxalates, etc. Since testing is not available for all types of adverse food reactions, and elimination / re-exposure diet remains the gold standard for identifying symptom-producing foods.
IgG antibody test
In food antibody testing, Genova uses the sandwich ELISA method to deliver semi-quantitative serum levels of IgG antibodies to food. The relative levels of IgG present for each food are reported using a semi-quantitative level:
- negative (none detected)
- VL (very low)
- Low (+1)
- Moderate (+2)
- High (+3)
When performing these assessments, Genova analyzes partial proteins, known as epitopes, to assess IgG antibody responses. Epitopes are designed to reveal the portion of the protein that most defines the specific food. There are no standardized, FDA-approved laboratory tests for the detection of IgG antibodies to food antigens available in the US market. Genova uses commercially prepared antigens for the evaluation of food IgG antibodies. IgG reactivity levels are standardized according to the international standard of the World Health Organization: immunoglobulins G, A and M, human serum NIBSC code: 67/086.
What Can Doctors and Patients Expect from Food IgG Antibody Tests?
In general, the clinical management of food-sensitive patients involves the removal or rotation of highly reactive foods. Doctors and patients often notice an improvement in symptoms after diet modification. Patients can tolerate food in small amounts, without symptoms, after several weeks or months of elimination. Increased intestinal permeability (leaky gut) can be treated simultaneously with diet, botanicals, and nutraceuticals, as well as by modifying contributing factors.