Tackling The Issues Behind Food Allergies By Sarah Groom, Karen Wiles and Katherine Baker
What is an Allergy? n An allergy is an immunological response initiated by the immune system to a normally harmless substance. (The food allergy and anaphylaxis network, 2002) n There are different types of allergies and they can be classified in different ways according to conventional and environmental allergists. n Conventional: Classified by the immune response that occurs. –Type 1: Antidodies of the IgE class cause this reaction. In a reaction histamine and inflammatory substances are from the cells. The results in inflammation, redness and itching.It affects the nose, eyes, lungs and intestines and can lead to involuntary expulsion efforts such as sneezing and coughing. This is also known as an atopic reaction and as results sufferers may have asthma, eczema and rhinitis. –Type 2: Caused by antibodies of the IgG and IgM class when they combine with complement to kill antigen cells. –Type 3: Caused by antibodies of the IgG and IgM class and complement. The damage is caused by the inflammation action of complement. The area doesn’t itch but it is very tender. –Type 4: Caused by natural killer cells and not antibodies. These cells kill invading microorganisms externally. Also known as contact allergies. (Readers Digest, 2001). – Environmental: Environmental allergies make the patient ill and occur in two patterns. –Type A: Includes most types which are recognised by immunologists. –Type B: Often have delayed effects or effects in other parts of the body (Readers Digest, 2001). n PSEUDOALLERGIES are reactions where the trigger has a direct effect on basophils and mast cells (immune system cells). This causes cells to degranulate and produce histamine and other inflammatory substances. The reaction isn't actually allergic.
What if you’ve got an Allergy? A food allergy should be suspected if the onset of symptoms appear after eating a certain type of food. If a particular food cannot be pinpointed then a food diary should be kept where all foods including snacks should be reported. Closely related foods often share allergens and allergic reactions may not always occur after heating because the allergen maybe weakened or destroyed. Other foods may become trouble after processing (Readers digest, 2001). Food allergy can cause or complicate many allergic conditions, including areas not obviously associated with eating and digestion. E.g. asthma, urticaria (nettle rash), anaphylaxis, eczema, rhinitis and laryngeal oedema. Fig1: The process of an IgE mediated allergic reaction (www.agbios.com/articles/ 2000151- A.htm)
Food Intolerance: If someone is intolerant to a food they experience a reaction which is neither an immediate allergy or a hidden allergy. There are four main intolerance mechanisms: 1.Enzyme defects: The intolerance can be caused by a defective enzyme. An example of which would be lactose intolerance due to the absence of lactase. 2. Pharmacological Effect: Caused by a direct action of a substance in the food such as caffeine in coffee. 3. Interaction With a Drug: Substances within food react adversely with drugs causing intolerance reactions. E.g. amines found in anchovies may interact with some antidepressants! 4.Toxins in Food: An adverse reaction is caused by the toxic effects of a substance in the food. An example would be lectin found in kidney beans which aren’t properly cooked (Reader’s Digest, 2001). Hidden Allergies: The mechanisms of hidden food reactions are not well understood. Sufferers are often sensitive to more than one food and even though a food is causing symptoms, its avoidance may cause withdrawal effects and worsen the situation. Common symptoms of hidden food allergies include asthma, rhinitis, migraine, muscle pain, fatigue, glue ear, Crohn’s disease, irritable bowel syndrome, insomnia, infantile colitis and even nephrotic syndrome (Reader’s Digest, 2001).
Cow’s Milk Protein n Cow’s milk protein is a major source of allergy in infants. Symptoms manifest themselves as problems in the gastrointestinal tract, on the epidermis, and in the airways. Hypersensitivity to cow’s milk persists into early childhood but is rare in adulthood. Cow’s milk contains over 20 different proteins, with five that can cause major allergic reactions. These are: Casein; ß-lactoglobulin; -lactalbumin; Immunoglobulins; and Bovine serum albumin Reactions to only one of these proteins is relatively rare, as usually two or more are involved in initiating an immune response (Mygind et al., 1996). n Cow’s milk allergy is thought to occur in 2-5% of infants, 50% of which may go on to develop an allergy related to another food (The Institute of Food Research, 2002). n People with cow’s milk allergy find suitable alternatives offered from Soya and rice milks.
Eggs, Fish, Wheat, Legumes n The major allergens present in hen’s eggs are ovomucoid and ovalbumin, both of which are contained within the egg white. Ovalbumin is relatively heat labile, while ovomucoid is resistant to heat, acid and proteloytic enzymes. People with an egg allergy are usually allergic to both cooked and raw forms of egg, but will tolerate meat from the chicken. Problems can occur when patients are administered vaccines grown on egg such as the MMR injection (Mygind et al., 1996). n Wheat flour can cause three main type of diseases. These are gluten entrophy (coeliac disease), inhalant allergy and food allergy. Wheat flour protein contains approximately 20 known allergens. The alergenicity of wheat proteins is dramatically reduced by digestion by protelytic enzymes in the gastrointestinal tract (Mygind et al., 1996). n Allergens found in fish can be common allergens and species-specific allergens. Allergens found in fish are resistant to heat, so patient will react to all types or raw or cooked fish. All cases of fish allergy are IgE mediated and symptoms can appear within minutes. Symptoms include angioedema, anaphylactic shock, gastrointestinal symptoms and urticaria (Mygind et al., 1996). n The peanut is not a nut and is in fact a legume. Potent allergens are present in peanuts and have been known to cause anaphylactic shock. The allergens in peanuts retain their allergenicity after roasting. People with a peanut allergy have the added problem that peanuts are often added as a nutritional supplement in many foods (Mygind et al., 1996). et al
Summary of Research and it’s Issues: n As already discussed in the report, there is a need to distinguish between food allergy and intolerance. This is reported as one of the reasons why the public perception of food allergy is high when in fact many may have a food intolerance (Food Standards Agency, 2002). It is reported that 2-8% of children and 1-2% of adults have a food allergy. Recent research states that food allergy incidence is rising (Kimber and Dearman, 2001). n The high incidence of self diagnosis have been shown by Altman and Chiaramonte (1997). In this study questionnaires were completed by 3775 homes. The results were that between 1989-1993 there was public perception that 1.17 individuals with a food allergy lived in their home the percentage reporting this was 13.9- 16.6%. This supported research of a high public perception of food allergies but not the rising incidence of food allergies. n On of the issues highlighted in the research is that through the use of double blind placebo controlled food challenges ( DBPCFC) the high prevalence of food allergies isn’t found with only 40% being tested as positive (Altman and Chiaramonte, 1997). n Several scientific articles have presented the’ hygiene hypothesis’. This is that exposure to allergens in youth protects against future allergic reactions. This is suggested to be one of the reasons why the incidence of food allergies is rising in westernised societies which employ stringent hygiene practices and use antimicrobial additives (Kimber and Dearman, 2001; Helm and Burks, 2000). n Food hypersensitivity reactions such as ulcerative colitis and Chrons disease are discussed as results of cytokine imbalance, white blood cell interactions and due to epithelial barrier dysfunction (Helm and Burks, 2000).
Summary of Research and it’s Issues n A s research develops there is a need for industry to keep abreast of new developments to benefit their allergic customers wherever they can. Formanek (2001) proposes that the best approach would be a partnership between researchers and industry to improve areas such as labelling. Labelling should be inclusive of all ingrediants and in understandable language, this was one of the issues discussed in the report. n Other issues which are highlighted by research into this area are of the claim that food allergies are responsible for migraines, hyperactivity, poor concentration or depression (Formaanek 2001). n Other issues which arose in the research were of controversial diagnostic techniques (e.g. cytotoxicity testing) which have been found to exhibit varying efficacy in scientific studies (Formaanek 2001). The image below shows a kit used in food allergy testing (Fig. 2). n Fig 2. An example of a kit used in food allergy diagnosis. (York Allergy U.S.A., 2002).
Summary of Research and it’s Issues n One of the issues associated with research into this area is of technological processing. This is because technological processing changes the structure of proteins. These changes might for example cause post translocational glycosylation, which increase the affinity of the protein for its receptor and thus increases its uptake in the intestine and its antigenicity (Helm and Burks, 2000). n This is significant as it is suggested by Kimber and Dearman (2001) that it is not completely understood which properties give a protein allergic potential. n This relates to the development of genetically modified foods which could introduce new allergens into the food chain (Helm and Burks, 2000). n FUTURE RESEARCH n Currently it has not been determined if immune cells are being stimulated to migrate to the site as a response to inflammation and injury or are in fact part of the causative mechanism of food allergy n It is hoped that future research into concepts such as ‘Th2 hypothesis’ where synergy between actions of Th1 and Th2 is used to explain inhalant allergy can be applied to determine mechanisms which explain food allergies (Helm and Burks, 2000). n Possibly in the future research on the subject of interactions between the intestine and the spleen will generate new hypotheses into how exactly a food allergy occurs (Helm and Burks, 2000).
Summary of Research and it’s Issues n Other questions to be answered include what gives an allergen allergy causing potential?, what makes an allergen persistent and severe?, what genetic differences confer susceptibility to food allergies?, how significant is stability of the allergen in gastric juices and how significant is pre natal exposure to allergens? (Kimber and Dearman, 2001). n Other avenues of research might progress from this to aid immunotheraphy treatments. Currently techniques are used to promote T-cell anergy using peptides (such as T cell epitopes which can’t bind IgE). For explanation of the role of IgE see slide 2. It is expected that this and the development of animal models in which a food induced anaphylactic shock can be induced or vaccinations against food allergies can be tested will advance food allergy research further (Helm and Burks, 2000). n The interactions between the various factors described will be clarified by further research into the subject and are depicted below (fig 3). n Fig 3. The interactions between the various factors causing a food allergy (Kimber and Dearman, 2001).
Conclusion n Food allergies are increasing in prevalence, and are a hot topic of research. n Not only are food allergies/intolerances reported in scientific journals, but the media is following the trend, which is contributing to public awareness, and in some cases paranoia. n Although approximately 20% of the population think they have a food allergy/intolerance, the actual figures are nearer 1 - 2% n Maybe it would be best if there was more media coverage on the subject to try and reduce the public belief that they are a sufferer. The correct reporting of the facts may reduce bad dietary habits and the public should be administered the correct advice. n A better strategy for the media to employ could be to include information in food allergy articles about what constitutes a healthy diet (i.e. including the food pyramid). They could also suggest foods to replace foods which have been eliminated from the diet, i.e. if dairy products are omitted green vegetables could be consumed to provide an alternative source of calcium.
References: 3 Altman, D.R. and Chiaramonte, L.T. (1997) ‘Public perception of food allergy’. Environmental Toxicology, 4, 95-99 3 The Food Allergy and Anaphylaxis Network, 2002. ‘Frequently Asked Questions About Allergies’. (online) http://www.foodallergy.org/questions.html. Accessed April 2002.http://www.foodallergy.org/questions.html 3 Formanek, R. (2001) ‘Food Allergies: When food becomes the enemy’. (online) http://www.fda.gov/fdac/features/2001/401_food.html Accessed April 2002. http://www.fda.gov/fdac/features/2001/401_food.html 3 Food Standards Agency (2002) ‘Food allergy and food intolerance’ (online) http://www.food.gov.uk Accessed April 2002. http://www.food.gov.uk 3 Helm, R.M and Burks, A.W. (2000) ‘Mechanisms of food allergy’. Current Opinion in Immunology, 12,647-653. 3 Kimber, I. and Dearman, R.J. (2001) ‘Food allergy: what are the issues?’ Toxicology Letters, 120, 165-170. 3 Levy, J. (ed), (2001). Health and Healing the Natural Way: Fighting Allergies’. Reader’s Digest, Reader’s Digest Association LTD, London, pages 16-98. 3 Mygind, N., Dahl, R., Pedersen, S., Thestrup-Pedersen, K., (1996). ‘Essential Allergy’., Blackwell Science, London, pages 131-149 3 York Nutritional Laboratories (2002) Allergy Testing (online) http://york.allergyusa.com/pinprick.htm. Accessed April 2002. http://york.allergyusa.com/pinprick.htm