PH: How common is food intolerance?
The charity Allergy UK claims that up to 45% of the population suffers from food hypersensitivity1.
PH: What are the most common health problems linked to food allergy?
Typically a wide range of symptoms from fatigue, headaches, migraine and skin problems, to bloating, stomach pain, nausea, diarrhoea, vomiting, IBS, joint pains, catarrh and runny nose.
PH: What’s the difference between food allergy and intolerance?
IgE-mediated food allergy is an inappropriate and harmful response of the immune system as it mistakes perfectly normal substances and treats them as invaders. Allergic symptoms can range from relatively minor rashes through to generalised swelling or collapse as a potentially fatal anaphylactic shock occurs. An allergic reaction can occur quite rapidly, often within minutes but generally within a maximum of two hours. Food Intolerance is quite different, it is not life threatening although it can and does make the sufferer feel unwell. It is very difficult to identify the food that is causing the problem as symptoms can appear up to 48 hours after the food is eaten. There is much confusion, particularly in the media, about different types of food hypersensitivity and how they manifest themselves. Frequently we find that food allergy and food intolerance are confused with each other. This is not surprising when you look at the raft of different mechanisms involved.
PH: What causes most food allergies or intolerances?
There are several mechanisms by which an individual may have an adverse reaction to food.2 Food hypersensitivity can involve reactions from the body’s own immune system such as:
- IgE Allergy – the most commonly known, immediate and potentially fatal response to foods (such as peanuts).
- Coeliac Disease – blood tests for Coeliac disease look for specific antibodies; tissue transglutaminase antibody and endomysial antibody. However, a few people with Coeliac disease do not have raised levels of these.
- Delayed onset food allergy, often referred to as food intolerance – Measurement of food-specific IgG antibodies is used as a strategy to identify foods to which an individual may be sensitive. Validated tests such as YorkTest First Step and YorkTest FoodSCAN113 are not diagnostic of any condition, but are used by those with chronic conditions, and with Nutritionist support, as an ‘aid to management’ of dietary intake.
IgE Allergy, Coeliac disease and delayed onset food allergy require different tests to identify them, and different management. Food sensitivity can also arise from mechanisms that do not involve the body’s immune system. These include adverse reactions due to enzyme deficiencies, for example lactose intolerance, and chemical sensitivities such as reactions to food additives like tartrazine (E102) and sunset yellow (E110).
PH: Doesn’t everyone produce IgG antibodies to the food they eat?
It is true that some studies have found no difference in food-specific IgG titres between patients with suspected or confirmed food hypersensitivity and control subjects. However, there are an increasing number of studies that demonstrate significantly higher levels of food-specific IgG in certain patient groups. To give a few examples:
Higher proportion of patients with IBS were IgG-positive for three common food components compared to blood donor control subjects.3 Significantly higher IgG titres to five out of 16 foods tested (wheat, beef, pork, lamb and soya bean) were observed in patients with IBS compared to healthy control subjects.4 Comparison of levels of IgG subclass antibodies to three cow's milk proteins (ß-lactoglobulin, a-lactalbumin and a-casein) in adults with asthma, eczema or both due to milk hypersensitivity with IgG levels in two control groups: blood donors and adults with asthma or eczema due to inhalant allergy. Apart from one blood donor, high levels of IgG subclass antibodies to all three milk proteins were found only in the patients with milk hypersensitivity.5 IgG antibodies to dietary antigens are strikingly increased in the gut of patients with rheumatoid arthritis and that food problems related to this may reflect an adverse additive effect of multiple reactions mediated, for example, by immune complexes promoting autoimmune reactions in the joints.6 Food-specific IgG levels are higher in patients with inflammatory bowel disease, compared to healthy controls.7 Obese children have significantly higher food-specific IgG antibody values directed against foods than normal weight children. Also that these food-specific IgG antibodies are “tightly associated with low grade systemic inflammation”.8 Of those coming to YORKTEST with chronic ill health symptoms, around 75% will have a positive IgG reaction to one or more foods. However, it is also clear that some individuals can tolerate the presence of raised food-specific IgG levels without showing symptoms. We advise that only those with symptoms use our food-specific IgG testing service.
PH: Does a person’s food sensitivities vary in time?
Some types of food sensitivity do not vary in time, but we have found that delayed onset food allergy, treated using a strategy based on measurement of food-specific IgG antibodies, can, with avoidance of the culprit foods, resolve itself in time. Only one published study has re-measured food-specific IgG at the end of the food elimination period and has shown a drop in levels for the excluded foods.9 The association between reduced IgG levels for excluded foods and symptomatic improvement is consistent with the hypothesis that the food-specific IgG may be playing a direct role in symptom initiation or exacerbation.
PH: How do you know that a test is reliable?
In order to show that results from a specific diagnostic test are meaningful, and can be interpreted and acted upon accurately and effectively, it is absolutely essential that tests undergo rigorous evaluation to make sure that they perform well enough to provide accurate and reproducible information. The thorough validation of a test’s performance can be divided into two categories: 1) Technical validation within the laboratory to ensure that systemic errors (leading to inaccuracy) and random errors (leading to poor reproducibility) have been minimised. 2) Clinical validation confirming the test’s potential in a clinical setting. My review of the fundamentals to look for when choosing laboratory testing services has recently been published.10 To ensure that the results being issued by the laboratory are correct, YORKTEST Laboratories test 'control' samples alongside samples from customers. The laboratory knows exactly what these control samples contain, so the samples act as a built-in check on the process of analysis. The control samples contain both high and low concentrations of the IgG antibodies being measured, to make sure that the procedure is operating correctly across the range of concentrations the patient samples may contain. If the control results vary from the known quantities, laboratory staff immediately know that there is a problem with testing and will not issue the result. The FoodScan 113 test is very accurate with greater than 93% reproducibility. Unlike other unproven food intolerance tests in the market, the YORKTEST FoodScan 113 uses a reputable scientific ELISA method to test for levels of IgG antibody reactions to specific foods which is a different method to classical allergy testing for IgE antibodies. With clinical trials and scientific validation, it is the only food intolerance test that has been independently proven. Details of the clinical evaluations that the YORKTEST FoodScan 113 test has undergone can be found in the recent review paper written in conjunction with the University of York.11 With the backing of Allergy UK, the YorkTest FoodScan113 remains totally focused on helping the 12 million people in the UK suffering the long battle with food intolerance and its associated symptoms.
PH: Why are dieticians often dismissive of food intolerance testing?
The classical and widely used method used by GP’s and dieticians in the NHS is the gold standard elimination diet and challenge approach. This approach is limited by the fact that it is expensive, lengthy and requires a high level of patient compliance. Furthermore, it can give rise to false negative challenges, for example due to an insufficient dose of challenge food, insufficient duration of challenge, or long lag times post-challenge before symptom exacerbation. It is also clear that it is well nigh impossible to test all the different combinations of food types that may be causing the problems. The strategy for elimination diet based on food-specific IgG can give those with chronic symptoms a route map to enable them to manage their diet and reduce their symptoms. The fact that individuals see a return of symptoms on reintroduction of culprit foods identified by the food-specific IgG test supports the fact that this is an active and specific approach. It is time these facts were recognised and brought into mainstream medicine and dietetics.
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1. Allergy UK Report (2007), “Stolen Lives 3, The Food Allergy and Food Intolerance Report”.
2. Johansson, S.G., Bieber, T., Dahl, R. et al. (2004), “Revised nomenclature for allergy for global use: Report of the Nomenclature Review Committee of the World Allergy Organization, October 2003”, Journal of Allergy and Clinical Immunology, Vol. 113, pp. 832-36.
3. Finn, R., Smith, M.A., Chew, D. et al. (1987), “Immunological hypersensitivity to environmental antigens in the irritable bowel syndrome”, British Journal of Clinical Practice, Vol. 41, pp.1041-1043.
4. Zar, S., Benson, M.J. and Kumar, D. (2005), “Food-specific serum IgG4 and IgE titers to common food antigens in irritable bowel syndrome”, American Journal of Gastroenterology, Vol. 100, pp. 1550-7.
5. Shakib, F., Brown, H.M., Phelps, A. et al. (1986). “Study of IgG sub-class antibodies in patients with milk intolerance”, Clinical Allergy, Vol. 16, pp. 451-8.
6. Hvatum, M., Kanerud, L., Hällgren, R. and Brandtzaeg, P. (2006), “The gut–joint axis: cross reactive food antibodies in rheumatoid arthritis”, Gut, Vol. 55, pp.1240-47.
7. Inns, S.J., Emmanuel, A.V., Hurel, S. and Bloom, S.L. (2007), “Prevalence of IgG food-specific antibodies in IBD: a case-control study”, Gastroenterology, Vol. 132, Suppl. 2, A-655.
8. Wilders-Truschnig, M. et al, (2008), “IgG Antibodies against food antigens are correlated with inflammation and intima media thickness in obese juveniles”. Exp Clin Endocrinol Diabetes Vol. 116, pp. 241-245.
9. Marinkovich, V. (1996), “Specific IgG antibodies as markers of adverse reactions to foods”, Monographs in Allergy, Vol. 32, pp. 221-5.
10. Hart, G. (2008), “Fundamentals to look for when choosing laboratory testing services”, Nutrition Practitioner, Spring/Summer edition.
11. Hicks, K. and Hart G., (2008), “Role for food-specific IgG based elimination diets”, Nutrition and Food Science, Vol. 38(5)