See all issues here


Food allergen myths debunked - Part 1

July 2014

Given the life-threatening nature of food allergies, one would think that the stakes are too high for myths and pseudoscience. Unfortunately, this is not the case and confusion surrounding these conditions abounds.

But who is responsible for this confusion?
- Is it physicians not keeping up-to-date with science, offering ill advice and misdiagnosing reactions?
- Is it consumers looking frantically for answers and relying on unsound sources to make self-diagnoses?
- Is it the internet with its abundance of unregulated information – some true, but much not?
- Or is it marketers of alternative-medicine providers conjuring up their own definitions of allergies and conveniently offering their own ‘cures’ to ‘fix’ these?

Neither one is solely responsible, but rather it is likely the combination of these misinformation sources that cause food allergy myths to spiral out of control.

Food producers, in particular, need to be cognisant of these myths, especially since their consequences may manifest in the manner in which allergens are controlled and how their risks are conveyed to consumers.

This two-part newsletter aims to dispel a few of the common myths surrounding food allergy and to shed light on the true nature of these adverse reactions and their impacts on potential sufferers.

 

Myth #1: Any adverse reaction to a food is an allergy and most people have one

With the great deal of media attention surrounding food allergies, it is not surprising that over 30% of the population believe that they have a food allergy and 30% of parents think that their children have at least one.

The truth: According to the World Allergy Organisation (WAO), approximately 1 - 2% of adults and 5 - 8% of children genuinely suffer from true food allergies. Thus, the true prevalence of food allergy is considerably lower than the perceived prevalence. Much of the confusion surrounding food allergy likely stems from the very poor understanding of the condition and the fact that both the public and health-care providers often erroneously attribute any adverse food reaction – ranging from intolerances to food poisoning – to an allergy.

How did this myth arise? Incorrect medical diagnoses, sloppy studies and distorted messages sent via lay press and marketers, likely lead many more people to think they have food allergies than is actually the case.

 

Food allergy vs. food intolerance: the facts

Food allergies and intolerances are not identical. Differences between these adverse reactions include the mechanism by which they proceed and the involvement of the immune system, as well as the food component responsible for eliciting the reaction.

Food allergy is an abnormal immune response to one or more of the proteins in a food, which the body mistakenly perceives as being ‘harmful’. Ingestion of even tiny amounts of an offending food can trigger reactions, which typically affect the skin, respiratory tract, gastrointestinal tract and cardiovascular system. Symptoms of food allergies range from mild to fatal, the onset of which is normally immediate (within minutes), although delayed allergic reactions also occur.

Food intolerance is a term used to describe various physiological responses to foods or food components, but which do not involve the immune system and do not proceed via allergy-like mechanisms. Food intolerances can include, amongst others, enzymatic defects (e.g. lactose or fructose intolerances, where the body lacks the enzymes to break down these compounds) and pharmacological responses (reactions to naturally-derived or added chemicals in foods). The onset of intolerance reactions is generally slower than in food allergy, but the symptoms can be similar and are often confused.

Myth #2: Celiac disease is an allergy to gluten

The terms ‘celiac disease’, ‘gluten allergy’ and even ‘gluten intolerance’ are often used interchangeably, but these are not the same thing…

The truth: Celiac disease is a hereditary, life-long disorder of the small intestine, caused by the ingestion of gluten. The term ‘gluten’ is usually used in the medical literature to refer to the proteins in wheat, rye, barley and possibly oats that are responsible for causing adverse effects in celiac sufferers. While celiac disease does involve an auto-immune response, it is neither a true allergy nor a true food intolerance and it does not follow the same mechanism as either of the latter. The symptoms of celiac disease are generally not immediate as with food allergies, however, they can be just as damaging. These include small intestine damage, nutrient malabsorption and potential secondary diseases such as anaemia and vitamin deficiency. Celiac disease is believed to affect 1 - 2% of the general population.

How did the myth arise? Much of the misinformation relating to celiac disease and allergies can probably be traced back to the lay press and self-diagnoses based on internet forums. While wheat is a recognised allergen, many people have probably misinterpreted this as referring to gluten. Wheat allergy is an immune reaction to one or more of the proteins in wheat only, thus wheat-allergic individuals may be able to tolerate rye and barley, but celiac sufferers will generally not tolerate all three.

Other news just in: Call to modify ‘gluten-free’ definition by Chilean regulators

The Chilean Ministry of Health has proposed that the definition of ‘gluten-free’ in the Food Health Regulations (Decree 977/96) be modified so that the term and its symbol can only be used on foods testing for =1 ppm prolamin. This proposed threshold is considerably lower than the 20 ppm gluten level defined by Codex and adopted by most other jurisdictions, including South Africa, regulating ‘gluten-free’ claims. While the intention of the Chilean regulators is undoubtedly to protect celiac sufferers, the effects of this modification will not only lead to fewer ‘gluten-free’ products being available on the market, but it will also pose a significant challenge in terms of verifying the claims using the existing analytical techniques. Currently available detection methods (ELISA and dipstick devices) have not been specifically developed and validated to detect gluten at such low levels. It thus remains to be seen whether this proposed amendment will be enforceable and if there are real benefits in having limits that are so much stricter than those issued by other jurisdictions.

Source: AOAC Food Allergen Community Newsletter 5(1), 2014.

Myth #3: Allergic reactions to seafood are due to iodine

There is a widely-held misconception that iodine is the compound responsible for causing both seafood allergies and adverse reactions to radio-contrast media or ‘dyes’ administered intravenously during CT scans.

The truth: Allergies to seafood (fish, crustaceans and molluscs) have nothing to do with iodine, nor are they related to adverse reactions to radio-contrast media. Iodine is not an allergen and no one is allergic to it. This trace mineral is, in fact, found in table salt and many other foods, and is required in the human diet for normal thyroid functioning. Rather, allergies to seafood occur due to the body’s immune response to one or more of the proteins present within the muscle tissue of these species, mainly the parvalbumin proteins in fish and the tropomyosins in crustaceans and molluscs. Several researchers have dispelled this myth in the scientific literature over the years, but the misconception has been hard to put to rest - primarily since the medical fraternity itself has helped to propagate it.

How did this myth arise? In a study conducted in 1975, it was observed that 15% of patients who experienced reactions to radio-contrast media also reported being allergic to seafood. The researchers thus inferred that iodine in both seafood and these media could be to blame. Largely overlooked, however, was that the same number of individuals in the study had also reported allergies to other foods e.g. eggs and milk. Nonetheless, many health professionals (mistakenly) began to and continue to inquire about a patient’s history of seafood allergy prior to administering radio-contrast media, a practice which has no scientific basis and which has only led the public to believe that such a link exists.

Note: Although reactions to contrast media can occur, these proceed via a non-allergic (non-IgE mediated) mechanism and are not due to iodine, but rather due to other substances in the contrast. A prior reaction to these media does not mean that seafood needs to be avoided and vice versa.

References
Beaty, A.D., Lieberman, P.L., Slavin, R.G. (2008). Seafood allergy and radiocontrast media: are physicians propagating a myth? American Journal of Medicine, 158: e1-4.
Chafen, J.J.S., Newberry, S.J., Riedl, M.A., et al. (2010). Diagnosing and managing common food allergies: a systematic review. Journal of the American Medical Association, 303:1848-1856.
Coakley, F.V., Panicek, D.M. (1997). Iodine allergy: an oyster without a pearl. American Journal of Roentgenology, 169: 951-952.
Huang, S.W. (2005). Seafood and iodine: an analysis of a medical myth. Allergy and Asthma Proceedings, 26: 468-469.
Katelaris, C.H. (2009). 'Iodine allergy' label is misleading. Australian Prescriber, 32:125-128.
Pawankar, R., Canonica, G.W., Holgate, S.T., Lockey, R.F. (Eds) (2011). WAO White Book on Allergy. Pp 47-53. Milwaukee, Wisconsin: World Allergy Organization.
Schabelman, E., Witting, M. (2010). The relationship of radiocontrast, iodine, and seafood allergies: a medical myth exposed. Journal of Emergency Medicine, 39:701-707.
Shehadi, W.H. (1975). Adverse reactions to intravascularly administered contrast media: a comprehensive study based on a prospective survey. American Journal of Roentgenology, 124:145-152.
Sloan, A., Powers, M.E. (1986). A perspective on popular perceptions of adverse reactions to foods. Journal of Allergy and Clinical Immunology, 78:127-33.
Woods, R.K., Stoney, R.M., Raven, J., et al. (2002). Reported adverse food reactions overestimate true food allergy in the community. European Journal of Clinical Nutrition, 56:31-36.

 

NEWSLETTER SNIPPET

Why is food allergy increasing?

The prevalence of allergic conditions, e.g., asthma, eczema and food allergy, has been steadily increasing. Researchers have no explanation for this; however a number of hypothesis have been proposed. Genetics does play a role but is not the major cause for this and other possible influences have been proposed. The hypothesis theory argues that not being exposed to "dirt", i.e., avoiding sources of microbial and other factors stimulating our immune system, results in a switch of our immune system to one favouring the development of allergies. Other proposed causes are the shift away from breast feeding of infants, starting infant feeding of solids too early, pollution, and additives and preservatives in food. However the evidence to support these theories are not robust and to date, no single obvious cause or causes have been identified to explain the increase.