Transcript Tackling The Issues Behind Food Allergies

Tackling The Issues Behind Food
Allergies
By Sarah Groom, Karen Wiles and
Katherine Baker
What is an Allergy?
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An allergy is an immunological response initiated by the immune system to a normally
harmless substance. (The food allergy and anaphylaxis network, 2002)
There are different types of allergies and they can be classified in different ways according
to conventional and environmental allergists.
Conventional: Classified by the immune response that occurs.
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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).
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/ 2000151A.htm)
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).
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).
Cow’s Milk Protein
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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:
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Casein;
ß-lactoglobulin;
a-lactalbumin;
Immunoglobulins; and
Bovine serum albumin
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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).
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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).
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People with cow’s milk allergy find
suitable alternatives offered from Soya
and rice milks.
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Eggs, Fish, Wheat, Legumes
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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).
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).
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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).
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).
Summary of Research and it’s Issues:
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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).
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 13.916.6%. This supported research of a high
public perception of food allergies but not
the rising incidence of food allergies.
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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).
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).
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
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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.
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).
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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).
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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
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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).
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.
This relates to the development of
genetically modified foods which could
introduce new allergens into the food
chain (Helm and Burks, 2000).
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FUTURE RESEARCH
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
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).
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
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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).
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).
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The interactions between the various
factors described will be clarified by
further research into the subject and are
depicted below (fig 3).
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Fig 3. The interactions between the
various factors causing a food allergy
(Kimber and Dearman, 2001).
Conclusion
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Food allergies are increasing in prevalence, and are a hot topic of research.
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.
Although approximately 20% of the population think they have a food
allergy/intolerance, the actual figures are nearer 1 - 2%
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.
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:
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Altman, D.R. and Chiaramonte, L.T. (1997) ‘Public perception of food allergy’. Environmental
Toxicology, 4, 95-99
The Food Allergy and Anaphylaxis Network, 2002. ‘Frequently Asked Questions About
Allergies’. (online) http://www.foodallergy.org/questions.html. Accessed April 2002.
Formanek, R. (2001) ‘Food Allergies: When food becomes the enemy’. (online)
http://www.fda.gov/fdac/features/2001/401_food.html Accessed April 2002.
Food Standards Agency (2002) ‘Food allergy and food intolerance’ (online)
http://www.food.gov.uk Accessed April 2002.
Helm, R.M and Burks, A.W. (2000) ‘Mechanisms of food allergy’. Current Opinion in
Immunology, 12,647-653.
Kimber, I. and Dearman, R.J. (2001) ‘Food allergy: what are the issues?’ Toxicology Letters,
120, 165-170.
Levy, J. (ed), (2001). Health and Healing the Natural Way: Fighting Allergies’. Reader’s
Digest, Reader’s Digest Association LTD, London, pages 16-98.
Mygind, N., Dahl, R., Pedersen, S., Thestrup-Pedersen, K., (1996). ‘Essential Allergy’.,
Blackwell Science, London, pages 131-149
York Nutritional Laboratories (2002) Allergy Testing (online)
http://york.allergyusa.com/pinprick.htm. Accessed April 2002.