This is very simplified information about food intolerance testing – there are more resources available at the end of the page for further reading for those who are interested in knowing more.
Food Intolerances are caused by problems with the metabolic system which usually means there is an enzyme deficiency which causes certain chemicals to build up in the body as they are not being processed, digested or removed properly. You are more likely to be suffering from a food intolerance than an allergy.
You can read more about different food intolerances on the dedicated Food Intolerance Page
There are a few tests for food intolerance that are well established, but they are outnumbered by other tests that are readily available and have little to no proof that they are effective.
Lactose Intolerance Testing
For lactose intolerance there is a simple test called the Hydrogen Breath Test. The amount of hydrogen in your breath is tested before and after you drink a liquid containing lactose. A high level of hydrogen on the breath after consuming the lactose drink would indicate that lactose has been undigested, because the levels are ordinarily low.
You can read more about Lactose Intolerance on the Food Intolerance Page
Coeliac Disease Testing
Coeliacs Disease can be identified by having a blood test and in some cases, a biopsy of the small intestine or imaging to confirm the diagnosis. You have to still be consuming gluten regularly for it to be identified by a blood test. The blood is tested for transglutaminase antibodies (referred to as tTGA) and endomysial antibodies (EMA) as the immune system can make these in response to the ingestion of gluten.
NICE, (The National Institute for Health and Care Excellence in the UK) recommend getting IgA and Transglutaminase Tests for diagnosis of coeliacs disease in adults.
A negative test may indicate an IgE food allergy to wheat or non-coeliac gluten intolerance (NCGI) for which there is currently no test for. An IgE food allergy can be identified by a blood test through your health provider.
You can find out more about coeliac (celiac) disease on the Food Intolerances Page
Elimination Diets and Reintroduction Diets
This is the ‘gold standard’ in the UK. There is no cost involved and it is sensitive to all adverse reactions. Although it can be time consuming and there is no way of confirming results, it is widely accepted by doctors as confirmation of a non-IgE mediated allergy.
To help with diagnosis it is advised to keep a food diary and note reactions to certain foods. After discussion with your health provider and referral to a dietician an alternative balanced diet can be agreed. A two to six week exclusion diet can be undertaken (depending on severity of symptoms) after this time you should see the dietician and/or health provider to discuss the next steps for prevention and treatment.
You can find out more about elimination diets and food diaries on the Food Allergy Diary Page
It is thought that a faster heartbeat after a problematic food is ingested may indicate a food intolerance. There is absolutely no evidence of a link between a faster heartbeat after food and a food intolerance.
Histamine Intolerance Testing
Histamine intolerance is caused by a DAO enzyme deficieny and is quite unusual in the general population. You can be tested to see if you are DAO deficient, but the result can never be completely accurate as histamine is a chemical in the body that is always present and is easily affected by diet and medication. In the UK under the NHS these type of tests are not usually offered.
You can find out more about histamine intolerance on the Histamine Page
Leukocytoxic testing (also called ATCAT (Antigen Leucocyte cellular antibody Test) is a food intolerance test where white cells in the blood are mixed with different food groups. It is claimed that if the cells well then you are intolerant to the food group. There is no evidence that this is a valid test for checking a food intolerance.
Vega Tests and Electroacupuncture (EAV)
Vega machines (also called Electrodermal Testing) are a type of electroacupuncture device dating from the 1970s (descendent of the 1950s EAV machines) which practitioners claim can diagnose allergies and other illnesses by measuring electrical pulses in the human body. Both NICE (National Institute for Health and Clinical Excellence) and BDA (British Dietetic Association) has advised against their use as there is no clinical proof that these machines are effective.
Kinesiology (Muscle Testing)
Developed in the 1960s, kinesiology relies on energy fields within the body to diagnose allergies and is popular with chiropractors. There is no evidence that these types of tests have any basis in science.
Hair testing for food intolerance is not scientifically valid. Some home tests for intolerance, like those for allergies, claim to be based on hair samples or ‘energy’ and are compared to similar samples in a database. These have no scientific basis whatsoever. Hair can be used to analyse drug use or different types of poison which accumulate in the body. Food intolerances are generally caused by the lack of an enzyme, this is not something which can be discovered by hair testing.
IgG Allergy Tests
These are blood tests which measures IgG and IgG4 antibodies to various foods. Most people develop these antibodies to food they eat and this is a normal non-specific response which indicates exposure to foods, but not sensitisation. IgG is the most common type of antibody found circulating in human blood.
You can have high IgG4 levels after cat allergen exposure, but this can indicate cat allergy protection, not sensitisation.
Despite the lack of scientific evidence of effectiveness IgG testing it is one of the most commonly offered blood tests available to buy for food intolerances.
What problems can bad food intolerance testing cause?
Using ineffective food intolerance tests can
Cost you a lot of money.
Can give you so many foods to avoid that it can cause deficiencies in your diet.
Can be used by companies to sell you additional supplements which will be of no additional benefit.
Please be very wary before trying new food intolerance tests and consider using one of the more well established methods.
Guts UK – Food Intolerance Testing
NICE (UK) Food Intolerance Testing Recommendations
British Dietetic Association – Food Intolerances
Allergy UK - Histamine Intolerance
Food intolerance in patients with functional abdominal pain: Evaluation through endoscopic confocal laser endomicroscopy, 2023
Issues surrounding consumer‐bought food‐allergy testing, 2022
Food Allergies and Intolerances: A Clinical Approach to the Diagnosis and Management of Adverse Reactions to Food, 2021
Living with Gluten and Other Food Intolerances: Self-Reported Diagnoses and Management, 2020
Food Intolerances, 2019
Unproven Diagnostic Tests for Food Allergy, 2018
Food-specific IgG4 lack diagnostic value in adult patients with chronic urticaria and other suspected allergy skin symptoms, 2010
Testing for IgG4 against foods is not recommended as a diagnostic tool: EAACI Task Force Report, 2008
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