3.1 FOOD INTOLERANCE AND FOOD ALLERGY
Over the last few years more and more information on allergies has become available but information on food intolerance is still sparse—the subject is often covered as part of a discussion on allergy but leaves out vast amounts of information that you need to know. I suspect that part of the reason for this neglect of food intolerance is because of difficulties with definition.
In the late to mid 1920s a more rigid definition of allergy began to appear and although doctors may have found this more “scientific” it effectively drew boundaries that have led to food intolerance problems often being ignored and, at times, even denied. Older definitions along the lines of allergy “is an unwanted reaction in the body or mind caused by a food or chemical” quite clearly encompassed what we now know as food intolerance. So don't be fooled—the term “food intolerance” does not refer to a less serious problem.
I use the term “food intolerance” to refer to adverse reactions caused by a food, naturally occurring food chemical or food additive. You will also see the same type of reactions referred to as “food sensitivity” and “food hypersensitivity”—this is simply because there is no single accepted term for what are classed as non-allergic reactions to food.
The difference between food allergy and food intolerance is primarily one of evidence in the blood. It used to also be the case that anaphylactic reactions were thought to only take place if an allergy was present. Unfortunately that is not the case anymore and anaphylactic reactions have been experienced by individuals with an intolerance of food additives such as sulphites[i] and nitrates[ii].
[i] Tarlo SM, Sussman GL. Asthma and anaphylactoid reactions to food additives. Can Fam Physician. 1993 May;39:1119-23.
[ii] Hawkins CA, Katelaris CH. Nitrate anaphylaxis. Ann Allergy Asthma Immunol. 2000 Jul;85(1):74-6.
[i] Tarlo SM, Sussman GL. Asthma and anaphylactoid reactions to food additives. Can Fam Physician. 1993 May;39:1119-23.
[ii] Hawkins CA, Katelaris CH. Nitrate anaphylaxis. Ann Allergy Asthma Immunol. 2000 Jul;85(1):74-6.
Soutter et al found that food intolerance is more likely to be a reaction to chemical substances found in many foods rather than the individual foods themselves. Symptoms are dose-related and may be cumulative from eating a range of foods containing the same substance. There can be a single symptom or a combination of a number of symptoms and these can vary over time. Reactions can take place within thirty minutes or up to forty eight hours after eating the problem food. They also found that preservatives and salicylates are the most likely to cause reactions but the range of substances that can affect a sensitive person varies from individual to individual.[Soutter V, Swain A, Loblay, R. Food allergy and food intolerance in young children. Asia Pacific Journal of Clinical Nutrition 1995;4(3):329.]
Other research has found that individuals react to various foods but when tested are not “allergic” so food intolerance, although often linked with food chemicals, can also be to any individual food. Future research may identify further chemicals that cause problems and clear this issue up but for the moment it is not known for definite what the actual cause is.
If your body cannot tolerate a particular food, or one of its ingredients, then you will experience an unwanted reaction. The type of symptoms that arise are very individual specific and it is not possible to say that, for example, apples will cause headaches or milk will cause stomach problems. They may do, but they may also cause other symptoms. The simple truth is that any reaction can be provoked by any food.
It is also important to understand that food intolerance is not the same as food allergy. In the case of an allergic reaction there is an immunological response that can be measured and “seen” in the blood. No such method of testing exists for food intolerance.
The safest, and most accurate, way of detecting food intolerance is by using an elimination diet that first removes the suspect food, in all its forms, from your diet and is then reintroduced. If there is a negative reaction, that food, for whatever reason, is not safe for you to eat. If, after a period of time, there is no reaction then the food is safe, for you, to eat. Without the aid of an appropriate blood test it is unlikely that you will know if your reaction can be defined as an allergy or intolerance problem. The situation is further complicated by the fact that reactions caused by allergy and intolerance are very similar.
In some instances it is possible to identify the cause of the intolerance. For example, many people cannot tolerate milk because they are lacking in the enzyme lactase which is essential for the digestion of lactose, the sugar found in milk. We also know that some substances, such as caffeine, act like drugs and we can point to a problem of overuse or overdose. Sadly, for most other forms of intolerance the situation is not as clear cut and if you find yourself intolerant of a food the odds are seriously stacked against you knowing the reason for your intolerance. Vatn suggests that the mechanism behind food intolerance is one of the greatest enigmas of modern medicine.[Vatn MH. Food intolerance and psychosomatic experience. Scand J Work Environ Health 1997;23 Suppl 3:75-8.]
Although this may be cause for concern for doctors and researchers, it need not concern you. Maybe one day they will ascertain the reasons, and maybe even find solutions, but until then you can still get healthier by avoiding the food or foods that cause you a problem. It is after all the case that many drugs have proved effective at removing or relieving symptoms yet little is actually known as to how some of these work—this is especially the case with drugs used to treat so called mental illnesses.
Testing Methods
An allergic reaction leads to an immunological response that can be measured and “seen” in the blood. No such method of identification, and hence testing, exists for food intolerance. The safest and most accurate, way of detecting food intolerance is by using an elimination diet that first removes the food, in all its forms, from your diet and is then reintroduced.
The three main types of medically approved allergy testing are:
- The Skin Prick Test where the suspected allergen is injected just under the surface of the skin and the reaction is observed. Not all allergies can be identified by this method.
- Patch Testing where the test substance is applied to the skin, covered with a patch and left in place for a period of time (up to 48 hours). Mainly used to establish if there is a contact allergy leading to some form of skin rash.
- Blood testing to detect the presence of an antibody called IgE in the blood. IgE is the substance that causes allergic reactions. Different substances produce specific IgEs and this enables the test to identify more than one allergen. Results are expressed on a grade that indicates how much IgE specific to the substance you tested for, is present in your blood. The higher the grade the more likely you are to be allergic.
The blood test used to only be available through the medical profession but there are some organisations that will now carry out these tests for you. You should note that a negative test does not 100% rule out an allergy. It is, also, possible to have a positive IgE test when you have either outgrown the allergy or not yet developed any symptoms. IgE testing will not identify a food intolerance problem.
The other main method of testing is a “food challenge” (sometimes called “oral challenge”). During a food challenge test, you are given the test food usually in gradually increasing amounts to see how you react. Whilst this is one of the most effective methods of testing for an adverse reaction to a food the medical profession does not generally like it as only one food can be tested at each appointment. It is also problematic for some doctors as they will not be able to say if the reaction is an allergic one or an intolerance one and for some medics the “correct” label is of great importance.
Other tests are available and some of these claim to identify food intolerances as well as allergies. The ALCAT test measures platelet aggregation and changes in white blood cells after mixing whole blood with various food extracts. Hoj [i] found it to be fairly reliable for identifying reactions to food additives but Fell et al found it far less successful in the testing of food allergies.[ii]
[i] Hoj L. Diagnostic value of ALCAT test in intolerance to food additives compared with double-blind placebo-controlled (DBPC) oral challenges. Presented at the 52nd Annual Meeting of the American Academy of Allergy, Asthma and Immunology, March 15-20, 1996, New Orleans.
[ii] Fell PJ, Brostoff J, O'Donnell H, et al. ALCAT - "a new test for food induced problems in medicine?" Presented at the Annual Meeting of the American Academy of Otolaryngic Allergy, October 1, 1988, Washington, D.C.
[i] Hoj L. Diagnostic value of ALCAT test in intolerance to food additives compared with double-blind placebo-controlled (DBPC) oral challenges. Presented at the 52nd Annual Meeting of the American Academy of Allergy, Asthma and Immunology, March 15-20, 1996, New Orleans.
[ii] Fell PJ, Brostoff J, O'Donnell H, et al. ALCAT - "a new test for food induced problems in medicine?" Presented at the Annual Meeting of the American Academy of Otolaryngic Allergy, October 1, 1988, Washington, D.C.
Provocative testing, using dilutions of food extracts are used by some practitioners and a similar procedure is used to “neutralise” or desensitise allergies. Although the efficacy of food extract injection therapy has been demonstrated in a double-blind study by Miller[i] others including Lehman[ii] failed to find a beneficial effect.
[i] Miller JB. A double-blind study of food extract injection therapy: a preliminary report. Ann Allergy 1977;38:185-191.
[ii] Lehman CW. A double-blind study of sublingual provocative food testing: a study of its efficacy. Ann Allergy 1980;45:144-149.
[i] Miller JB. A double-blind study of food extract injection therapy: a preliminary report. Ann Allergy 1977;38:185-191.
[ii] Lehman CW. A double-blind study of sublingual provocative food testing: a study of its efficacy. Ann Allergy 1980;45:144-149.
What you need to know before parting with your money is that food intolerance does not cause a specific response in the body that can be measured. Yes, it does sometimes cause a fluctuation in the pulse that can be detected and sometimes a measurable IgG but not always. Also, no one substance is produced in the blood that can be used to measure all forms of food intolerance. Given that any food can cause any reaction and that your food problems could in fact be being caused by food chemicals these tests need to approached with some degree of caution.
A common food allergy test, in commercial use, measures IgG in the blood. Kleine-Tebbe et al note that, whilst many of the samples showed positive IgG4 results, there were no corresponding clinical symptoms. This, combined with the lack of convincing evidence for histamine-releasing properties of IgG4 in humans, and the lack of any controlled studies on the diagnostic value of IgG4 testing in food allergy, call into question the value of these type of tests.
They argue that food-specific IgG4 does not indicate (imminent) food allergy or food intolerance. What it does indicate is a physiological response of the immune system to food components. They conclude that these type of tests should not be used to identify food related problems. It would seem that presence of IgG4 may only indicate that you have recently eaten the food identified and that your body has reacted as expected.[Kleine-Tebbe J, Reese I, Ballmer-Weber BK, Beyer K, Erdmann S, et al. No recommendation for IgG and IgG4 testing against foods. Allergo J 2009;4: 267.]
One of my concerns with these tests is that some people come away with a very long list of foods to be avoided. If they avoided all of these foods their diets would be very restricted. My own view is that, if this type of test is used as a diagnostic tool, it still needs to be followed up by individual testing of the identified foods (by eliminating the food and then reintroducing it) to confirm whether they are in fact causing a problem.
An excellent study by Joneja identifies the difficulties in testing for food allergy and especially for food intolerance. She concludes that no single method of testing can identify all problem foods or the constituents within the food because the immunological, physiological and biochemical reactions that effect food sensitivity are so diverse. Elimination and challenge testing often provide the most accurate results.[Joneja JM. Food Allergy Testing: Problems in Identification of Allergenic Foods. Can J Diet Pract Res 1999;60(4):222-230.]
Allergy testing is often seen as being well proven, scientific and accurate. In contrast, food intolerance testing is seen as unscientific and unproven. But just how accurate is allergy testing? Well, that depends... For example, skin prick tests are performed to identify the causes of allergy but when compared to results from oral challenges there has always been a great degree of inconsistency. Doctors have never been able to explain why this should be the case
A study of skin prick testing by Kim et al goes a long way to providing some answers. Quite simply, the results from skin prick tests significantly improves when fresh food is used for the test rather than commercial allergen extracts. The study focused on patients with atopic dermatitis and the allergens investigated were milk, egg white, egg yolk, and soya bean. What they found was that when you compare fresh food samples and commercial allergens they are different in structure. Most significantly some of the protein elements implicated in allergic reactions are missing in the commercial samples. [Kim TE, Park SW, Noh GW, Lee SS. Comparison of Skin Prick Test Results between Crude Allergen Extracts from Foods and Commercial Allergen Extracts in Atopic Dermatitis by Double-Blind Placebo-Controlled Food Challenge for Milk, Egg, and Soybean. Yonsei Medical Journal 2002: 43(5); 613-620.]
Before you rush of to your allergist and demand a different type of skin prick test it is worth noting that even though the fresh foods resulted in a greater degree of accuracy the percentages still did not reach the seventies. It would appear that oral food challenges and use of elimination diets are more accurate methods of testing.
Similar findings have emerged from other studies. Vojdani argues that one of the reasons traditional food sensitivity testing fails is that it does not reflect a real world non-raw food diet. The problem is not only that a food can change when processed but that the effect it has in the body can also be different when it is combined with other foods. So, a person “who is allergic to ketchup may not have an immune reaction to raw tomato”. Normal testing methods would not identify or resolve that individual’s problems. [Vojdani A. Detection of IgE, IgG, IgA and IgM antibodies against raw and processed food antigens. Nutr Metab (Lond). 2009 May 12;6:22.]
The reality is that identifying food related problems can be difficult. In some instances, the food culprit is very clear, in others a lot of work has to be done to find the problem makers. In yet other cases, the problem ingredient can be so hidden that it can easily be overlooked and missed. A case described by Leduc et al illustrates this—it was thought that an individual was allergic to wheat in sausages and pork pies but allergy testing to wheat was negative. It was only when the actual real-time ingredient, in this case wheat isolate, was tested that a positive reaction was confirmed. [Leduc V, Moneret-Vautrin DA, Guerin L, Morisset M, Kanny G. Anaphylaxis to wheat isolates: immunochemical study of a case proved by means of double-blind, placebo-controlled food challenge. J Allergy Clin Immunol. 2003 Apr;111(4):897-9.]
If you have ever suspected that you have an allergy and been sent for tests that have all turned out negative and been told there is nothing wrong with you, when you know there is, then don't despair—you are probably food intolerant.
Just because you can't measure it doesn't mean it doesn't exist.
In 1991 Sloper et al presented their findings on the links
between eczema and food in children and reported on their immunological findings. Although they were able to observe that eczema, for many of the children, improved significantly during the diet and became worse on food challenges, the clinical outcome of food elimination could not be predicted by the initial skin prick test results, serum immunoglobulins, total or food-specific IgE, or complex IgG or IgE. This study sends a very clear message that allergy tests are not, always, enough. [Sloper KS, Wadsworth J, Brostoff J. Children with atopic eczema. I: Clinical response to food elimination and subsequent double-blind food challenge. Q J Med 1991;80(292):677-93.]
between eczema and food in children and reported on their immunological findings. Although they were able to observe that eczema, for many of the children, improved significantly during the diet and became worse on food challenges, the clinical outcome of food elimination could not be predicted by the initial skin prick test results, serum immunoglobulins, total or food-specific IgE, or complex IgG or IgE. This study sends a very clear message that allergy tests are not, always, enough. [Sloper KS, Wadsworth J, Brostoff J. Children with atopic eczema. I: Clinical response to food elimination and subsequent double-blind food challenge. Q J Med 1991;80(292):677-93.]
What you have to understand is that an allergic reaction can be caused by a very small amount of the problem food, in respect of intolerance this is not generally the case. Food chemicals, such as salicylate and solanine, build up in the body and it is only when the individual's tolerance is breached that problems appear. Challenge testing with a concentrated form of the chemical can be misleading as most are cumulative in the body and the amount varies from day to day. A positive reaction is of no help in ascertaining the level you can in fact tolerate.
We all want a quick and easy answer but the reality is that this is not always possible. If you do use one of these tests and are presented with a list of foods to avoid, do not accept the list as definitive proof of your problems. By far the wisest course of action would be then to test each of these foods using an elimination diet. If you don't do this you could be restricting your diet far too severally and unnecessarily.
Why bother with an elimination diet when you know someone who has had massive improvements by following the advice given as a result of one of these tests? Because your health matters and what works for one person will not necessarily work for someone else. Two of the most common foods that people are asked to eliminate are milk and wheat and I think you will be a rare individual not to experience some positive health changes if you eliminate these but this is not always indicative of a food intolerance problem. Wheat and milk are two foods that are consumed daily, often at each meal, and removing them from the diet often leads to some improvement. It is possible that your body is simply enjoying a rest, that you are intolerant of gluten or are lactose deficient or that you have a problem with amines and so on.
In 2008 undercover researchers forWhich? trialled various tests that claim to diagnose food intolerances through analysis of blood samples or strands of hair, changes in electric current, or resistance to pressure applied to their legs or arms (the tests cost between £45 and £275 each). The researchers had one medically confirmed allergy and one food intolerance between them yet the tests diagnosed one hundred and eighty three intolerances. They also found that identical blood and hair samples sent under different names to the same company produced different test results. Their advice to people who are concerned that they may have an allergy or intolerance was “to keep a record of symptoms and a food diary, and speak to their GP”.[http://www.which.co.uk/news/2008/08/food-allergy-tests-could-risk-your-health-154711/]
Soutter et al in their study of food allergy and food intolerance in children state that food chemical intolerance can only be assessed by means of an appropriate elimination diet and challenge protocol. Blood and skin tests are not helpful or appropriate.[Soutter V, Swain A, Loblay, R. Food allergy and food intolerance in young children. Asia Pacific Journal of Clinical Nutrition 1995;4(3):329.] Sadly few doctors, allergists or other health practitioners are aware of the problems these chemicals can cause.
Elimination diets are the only accurate way of determining most forms of food intolerance and a simple easy to use system is outlined below in the Seven Step Plan.
Before you even think about following the plan you should consult with your doctor and ensure that there is no underlying illness.