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  • Doctors’ positions on food intolerance blood tests

    Doctors’ positions on food intolerance blood tests

    Food intolerance blood tests measure a person’s levels of IgG antibodies to a wide variety of foods, but IgG antibodies do not have any proven link to illness. At best, these blood tests are a waste of money; at worst, they can lead to poor or even dangerous health decisions.

    Despite their inherent ineffectiveness, IgG food intolerance tests have spread to the pharmacy and the doctor’s office, making it hard for the average patient to know where to turn for reliable information. To protect the public, professional medical associations in many countries asked the best minds in immunology to prepare position statements warning against these tests. Let’s take a look at some of the main points from these warnings in plain English.

    From the Australasian Society of Clinical Immunology and Allergy [1]:

    “IgG antibodies to food are commonly detectable in healthy adult patients and children, independent of the presence or absence of food-related symptoms. There is no credible evidence that measuring IgG antibodies is useful for diagnosing food allergy or intolerance, nor that IgG antibodies cause symptoms. In fact, IgG antibodies reflect exposure to allergen but not the presence of disease.” (full text)

    What it means

    The most important thing to remember is that everyone produces IgG antibodies to food. The concentration of IgG antibodies in your blood depends on your genes, your diet, and maybe even on how you were fed as an infant [2]. There is simply no ‘correct’ IgG level. This means that a healthy person could get the same diet recommendations from an IgG blood test as a person with symptoms.

    Looking at the entire body of available evidence, there is no correlation, let alone a causal link, between IgG antibodies and symptoms. In fact, using IgG test results to identify problem foods is no more successful than flipping a coin.

    From the European Academy of Allergy and Clinical Immunology [2]:

    “Food-specific IgG4 does not indicate (imminent) food allergy or intolerance, but rather a physiological response of the immune system after exposition to food components. Therefore, testing of IgG4 to foods is considered as irrelevant for the laboratory work-up of food allergy or intolerance and should not be performed in case of food-related complaints.” (full text)

    What it means

    You might think that not being allergic to a food – in other words, being “tolerant” to that food – means that your immune system ignores it. Sometimes that happens, but tolerance is often an active process. Regulatory T cells keep the immune system from reacting to potential food allergens, and it is these cells that call in the IgG antibodies by secreting an anti-inflammatory messenger chemical known as IL-10. IgG antibodies are not the sign or cause of anything bad, but rather a sign that a person has eaten and has tolerated a certain food. IgG antibodies have nothing to do with food intolerance.

    From the Canadian Society of Allergy and Clinical Immunology [3]:

    “The test is also being marketed to concerned parents, and may lead to exclusion diets which carry risks of poor growth and malnutrition for their children: for example, the elimination of dairy products, wheat, eggs, and/or other foods found in healthy balanced diets.” (full text)

    What it means

    IgG blood tests often identify between 5 and 20 suspect foods, so the risk of nutritional deficiencies in children is real if too many foods are eliminated without proper medical support. The bigger issue is whether these tests are actually related to the conditions they are purported to treat, namely ADHD and autism spectrum disorder (ASD); let’s take a look at that.

    ADHD. Some artificial colors have been shown to affect behavior in children with ADHD, but this reaction does not involve the immune system, so IgG blood tests are irrelevant for identifying which children might be affected. Other foods have also been shown to aggravate ADHD, but IgG levels could not accurately predict which foods. [4]

    Autism spectrum disorder. Since IgG blood tests do not really detect adverse reactions to foods, it is unlikely that these tests would apply specifically to autism. While there is speculation that a ‘leaky gut’ increases the likelihood that IgG antibodies to wheat and milk proteins will be found in the blood of children with ASD, a much-touted paper on the topic actually showed that IgG levels did not correlate with intestinal permeability [5].

    This doesn’t mean, though, that someone with autism couldn’t also suffer from food intolerance independent of IgG test results. For parents thinking about dietary interventions for autism, it might be helpful to consider the opinion of registered dietitian Zoe Connor, chair of the Dietitians in Autism group within the British Dietetic Association [6]:

    “…[A]lthough there is insufficient evidence to recommend the use of any diet as a treatment for ASD, dietitians and other health professionals should provide support when an individual or their parents choose to try dietary changes. There are too many reports of children with ASD improving in behaviour and/or bowel habits after eliminating some foods for them to be discounted. However, the mechanism for this (until proven otherwise) is likely to be the same as for any general food intolerance, rather than any specific disorder that is particular to ASD, and so each case should be considered individually. For example, bowel problems such as diarrhoea or constipation can sometimes be caused by food intolerances, so individuals suffering from these might benefit from trying different food exclusions (medical causes should first be investigated by a doctor).” (p. 66)

    From the American Academy of Allergy Asthma and Immunology [7]:

    “Additionally, and perhaps of greater potential concern, a person with a true immunoglobulin E (IgE)-mediated food allergy, who is at significant risk for life-threatening anaphylaxis, may very well not have elevated levels of specific IgG to their particular allergen, and may be inappropriately advised to reintroduce this potentially deadly item into their diet.” (full text)

    What it means

    In true food allergies, IgE antibodies bind with allergen proteins to cause chemicals, like histamine, to be released in the body and trigger symptoms. IgG antibodies are not interchangable with IgE antibodies, and IgG blood tests do not detect food allergies.

    We most often think of food allergies as beginning in childhood, but adults can also develop allergies at any time. Perhaps an old allergy returns, perhaps a mild allergy was there in the background all along, or perhaps the allergy is completely new. New allergies to pollen can also bring on food-related symptoms in the form of oral allergy syndrome. Adult food allergies must be taken seriously, because the risk for severe reactions becomes greater the later they develop [8].

    Approaching food sensitivities the right way

    The EAACI position statement [1] mentions another vulnerable market for food intolerance blood tests – people who see their doctor for a suspected food sensitivity that turns out not to be an allergy but cannot be explained. The doctor dismisses their symptoms, but not their suspicions of food. Feeling let down, they go outside the medical community for care or advice – which is understandable, but never the wise thing to do.

    In a case like this, the safest thing is to get a doctor’s referral to see a registered dietitian and discuss doing a diet investigation. Alternative medicine may use rhetoric about ‘hidden food intolerances,’ but a knowledgable dietitian can use your personal history and diet log to guide you through the elimination diet and food challenges that check for food intolerance. In actuality, there is nothing ‘hidden’ about food intolerance, and there is no need to resort to blood tests to find your food sensitivities.

    Last updated September 25, 2015

    References

    1. Australasian Society of Clinical Immunology and Allergy. Unorthodox Techniques for the Diagnosis and Treatment of allergy, Asthma and Immune Disorders – ASCIA Position Statement [Internet]. 2007 [cited 2014 Mar 10]. Available from: http://www.allergy.org.au/health-professionals/papers/unorthodox-techniques-for-diagnosis-and-treatment (Archived by WebCite® at http://www.webcitation.org/6OjZpQGNt).

    2. Stapel SO, Asero R, Ballmer-Weber BK, Knol EF, Strobel S, Vieths S, et al. Testing for IgG4 against foods is not recommended as a diagnostic tool: EAACI Task Force Report. Allergy. 2008;63(7):793–6. Available from: http://onlinelibrary.wiley.com/doi/10.1111/j.1398-9995.2008.01705.x/abstract (Archived by WebCite® at http://www.webcitation.org/6OjZbB9va).

    3. Carr S, Chan E, Lavine E, Moote W. CSACI Position statement on the testing of food-specific IgG. Allergy Asthma Clin Immunol. 2012 Jul 26;8(1):12. Available from: http://www.aacijournal.com/content/8/1/12 (Archived by WebCite® at http://www.webcitation.org/6OjZmUPVA).

    4. Pelsser LM, Frankena K, Toorman J, Savelkoul HF, Dubois AE, Pereira RR, et al. Effects of a restricted elimination diet on the behaviour of children with attention-deficit hyperactivity disorder (INCA study): a randomised controlled trial. The Lancet. 2011;377(9764):494–503.

    5. De Magistris L, Picardi A, Siniscalco D, Riccio MP, Sapone A, Cariello R, et al. Antibodies against Food Antigens in Patients with Autistic Spectrum Disorders. BioMed Research International. 2013;2013:1–11.

    6. Connor Z, Autism and autistic spectrum disorders. In: Skypala I, Venter C, editors. Food Hypersensitivity: Diagnosing and Managing Food Allergies and Intolerance. John Wiley & Sons; 2009. p. 63-68.

    7. Bock SA. AAAAI support of the EAACI Position Paper on IgG4. Journal of Allergy and Clinical Immunology. 2010 Jun;125(6):1410. Available from: http://www.jacionline.org/article/S0091-6749(10)00512-9/fulltext (Archived by WebCite® at http://www.webcitation.org/6OjZkm9m9).

    8. Kamdar TA, Peterson S, Lau CH, Saltoun CA, Gupta RS, Bryce PJ. Prevalence and characteristics of adult-onset food allergy. The Journal of Allergy and Clinical Immunology: In Practice. 2015 Jan;3(1):114–115.e1.

    Anna L. Laforest

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  • Unpredictable symptoms? It’s not always the last thing that you ate

    Unpredictable symptoms? It’s not always the last thing that you ate

    Sometimes it is easy to figure out food sensitivities – especially when they only involve one food or one kind of symptom. For example, lactose intolerance (a type of enzymatic food intolerance where people are deficient in the enzyme needed to digest milk sugar) is related only to milk and milk products, so it’s easy to notice the gastrointestinal symptoms after a nice bowl of ice cream with the kids. But other sensitivities are not so obvious.

    Take pharmacological food intolerance, or just ‘food intolerance.’ This type of food sensitivity has always been hard to pin down, on both an individual level and in clinical studies. Symptoms can arise hours or even days after you eat a trigger food, and their severity depends on how much you ate, whether you ate any other trigger foods in prior days, and if you have other health conditions or environmental sensitivities. Furthermore, your symptoms may be different from those of someone else who reacts to the same foods.

    On top of this, food intolerance is a reaction to chemicals that are found in a wide variety of foods. For example, if you were sensitive to histamine, you would need to watch out for fruits, meats, cheeses, chocolate, etc. If you were sensitive to artificial colors and preservatives, you would need to read every food label. This is different than food allergies, where people are oversensitive to the proteins found in specific foods. With food intolerance, your food journal wouldn’t be tracking the foods as much as the chemicals inside them. And that’s when things start to fall into place, because, as we’ll see, your symptoms aren’t always caused by the last thing that you ate.

    More information: Common food triggers

    How food intolerance works

    The term ‘pharmacological food intolerance’ underscores the idea that foods, no matter how natural, can contain chemical compounds that are foreign substances in our bodies (like benzoate in fruit or artificial colors in yogurt) or excess amounts of chemicals that our bodies normally produce (like tyramine or histamine in certain cheeses). These chemicals are referred to as xenobiotics, a term which also covers substances like medications, poisons, and environmental pollutants that enter our bodies. This means that pharmacological food reactions share characteristics that are already familiar to us from our experiences with other xenobiotics. In food intolerance:

    • The severity of your reaction depends on the dose. Below the threshold dose, no symptoms are observed.
    • Doses are additive across multiple meals. What you ate throughout the day, and even the previous day, counts towards your accumulated dose. Symptoms occur when the accumulated dose exceeds the threshold dose.
    • Multiple food chemicals can work together to exacerbate the effects of the others.
    • Withdrawal symptoms can occur.
    • You can become temporarily tolerant of a food chemical.

    The most important of these ideas is the concept of a threshold dose. If you are very sensitive to a food chemical, you have a low threshold, and a small amount is all that is needed to produce symptoms. If you have a high threshold, eating small amounts of a substance will not produce any symptoms. And it’s not necessary to consume all of your food chemical in one meal in order to exceed the threshold dose – little bits can add up over a couple of days. If you were looking to see which food caused your symptoms, you might find that it was several foods over several meals that all contained the same trigger chemical.

    In general, we can say that food intolerant people have lower dose thresholds than the rest of the population since most people do not react to food. This is partly due to differences in how well the body can rid itself of chemicals and partly due to how susceptible one is to experiencing adverse reactions – this is all part of the natural variations among people. However, it turns out that your personal threshold dose can also vary over time, depending on what else you have eaten, what medications you have taken, and other health-related factors.

    An example of accumulated and threshold doses

    Symptoms occur when your accumulated dose exceeds the threshold dose.
    Figure: Hypothetical dosage of amines over four days. The amount of chemical trigger in your body increases as successive meals are eaten.

    Consider the chart on the right that tracks meals over four days – simplified, of course, for a hypothetical person. If you experienced symptoms on Day 4, would your first inclination be to blame the spaghetti dinner and perhaps the gluten-containing pasta in particular?

    Our hypothetical person is actually sensitive to salicylate and amines, and she needs a mix of both to see symptoms – it turns out that honey, raspberries, guacamole, and tomato sauce all contain at least one of these chemicals. The chemicals accumulated in her body over the course of three days until her threshold dose (which, luckily for her, is rather high) was exceeded on the fourth day.

    Our person had wondered about gluten sensitivity in the past, but didn’t seem to react reliably to wheat. Now that she is mindful of her trigger chemicals and her threshold dose, she can eat some of the foods she likes without adverse effects.

    Bibliography

    Loblay R, Swain AR. Food Intolerance. In: Wahlqvist ML, Truswell AS, editors. Recent Advances in Clinical Nutrition. London: Libbey; 1986. p. 169–77.

    Swain AR, Soutter VL, Loblay RH. RPAH elimination diet handbook. Rev. ed. Camperdown, Australia: Allergy Unit, Royal Prince Alfred Hospital; 2011.

    Anna L. Laforest

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  • Diagnosing food intolerance

    Diagnosing food intolerance

    In this day and age, it’s hard to imagine medical tests that don’t draw blood or that don’t involve expensive, room-filling equipment; however, for food intolerance and some immune-mediated reactions, the tried and true diagnostic requires only a pencil, paper, and food. Doctors, dietitians, and medical researchers rely on elimination diets and food challenges to identify food sensitivities, which can be used regardless of the underlying mechanism – this is important because right now we have only rough ideas of how these some of these reactions might work.

    Diet investigations are deceptively simple – start from scratch and add only one potential trigger at a time until the culprit is found – but they also require a detailed knowledge of food chemicals. For this and for safety reasons – after all, you need to rule out if you actually have an allergy or another condition – you should always undergo a diet investigation with the help of a doctor or a registered dietitian. To help you prepare, let’s look at the three phases of the process: the elimination diet, the food challenges, and the modified diet. Before you start, your dietitian may also ask you to briefly keep a food and symptom journal to provide a baseline on the severity and frequency of your symptoms.

    Caution: The information here is provided to give you an idea of the diet investigation process; it is not a set of instructions to carry out the procedure yourself. Always check with a doctor or a registered dietitian before modifying your diet. The elimination diet/food challenge process is not appropriate for pregnant women. People with asthma or laryngeal edema (swelling in the throat/upper airways) should only undergo food challenges in a clinic where resuscitation facilities are available. People with Crohn’s disease should not try an elimination diet without medical supervision.

    Phase 1: Elimination diet

    The elimination diet consists of only a few foods that are unlikely to cause symptoms in most people; depending on your history, it might be less restrictive. You must adhere to the diet even if you think that you know which food chemical makes you ill because you might be sensitive to more than one chemical. In most people, symptoms improve after two to four weeks on the elimination diet. You may experience a withdrawal reaction (a flare-up of symptoms) after the first or second week.

    The elimination diet is necessary for several reasons. First, it indicates whether you are on the right track: if there is no change in symptoms after four weeks of strict adherence to the diet, then food intolerance is unlikely. Second, it removes the variability (the ‘noise’) in your symptoms so that changes can be detected during the food challenge phase. Finally, it lowers the amount of trigger chemical that you need to eat in order to see symptoms.

    Phase 2: Food challenges

    The food challenges determine which food chemicals are triggering symptoms. After at least two weeks on the elimination diet, specific foods are reintroduced into your diet one at a time – these are the ‘challenges.’ If a reaction occurs after a challenge, then you must wait until the symptoms subside, plus a few days, before moving on to the next food. Such challenges are referred to as ‘open’ challenges because you are aware of what you are eating. In research studies, participants are given food chemicals in capsules so they do not know which chemical is being tested or whether they are getting a placebo – these ‘blind’ challenges provide the most reliable diagnosis.

    Wheat and milk are often tested first because reactions to these foods are just as common as pharmacological food intolerance reactions; then salicylate, benzoate, amines, MSG, artificial colors, etc. are tested on the advice of your dietitian. Ideally, challenge foods would only contain one trigger chemical, but this is not always possible. When challenge foods contain more than one trigger, the ordering of the challenges is important to systematically rule out all possibilities.

    More information: Common food triggers

    Phase 3: Modified diet

    Your dietitian will design a modified diet for you based on your challenge results. You will be reevaluated in 1 or 2 months to see how well the restricted diet is working and to decide whether it is safe to liberalize what you eat. In this part of the process, you will be checking to see whether you have a high or low dose threshold for symptoms; you may also be able to gradually increase the amount of triggers that you eat, but, for your safety, you should always work on this with a dietitian or doctor. Since threshold doses can decrease after avoiding a food chemical, sensitive people could experience dangerous reactions when reintroducing foods to their diet, even in amounts that previously did not cause symptoms.

    More information

    Consult these books if you are interested in learning more about diet investigations:

    Bibliography

    Brostoff J, Gamlin L. Food Allergies and Food Intolerance: The Complete Guide to Their Identification and Treatment. Inner Traditions/Bear; 2000. 486 p.

    Clarke L, McQueen J, Samild A, Swain A. The dietary management of food allergy and food intolerance in children and adults. Australian Journal of Nutrition and Dietetics. 1996;53(3):89–98.

    Anna L. Laforest

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