Food Allergies and Intolerances

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Food Allergies and Intolerances

• H. Singh
• NTRS 525

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What Is A Food Allergy

• A food allergy is an adverse reaction to a food
  or food component that involves the immune system
• A food allergen is the part of a food a person is
  allergic to
• Food allergens are proteins not fat
  carbohydrates vitamins or minerals
• 2-5 in infants most common milk and eggs
• 2.4 in adults

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Who Has Food Allergies

• Although anyone can develop a food allergy the
  ability to become allergic tends to be inherited
• Many people who have food allergies also have
  asthma or show sensitivities to inhaled
  allergens such as dust cat and pollen

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What Happens WithA Food Allergy

• When someone eats a food they are allergic to
  the food allergen stimulates the immune system to
  release antibodies
• The antibodies cause body cells to release
  substances which cause allergic reactions

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Most Common Food Allergies

• Food allergies can occur to almost any food but
  most allergic reactions are caused by a limited
  number of foods
• milk shellfish
• eggs soy
• wheat peanuts most common anaphylaxis
• fish tree nuts like walnuts
• Additives preservatives flavoring coloring
  antioxidants cause Pseudo-allergenic reactions

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Where does it start

• According to a recent study the prevalence of
  peanut allergy--which accounts for the majority
  of emergency-room visits and deaths related to
  food allergies each year--doubled between 1997
  and 2002.
• The story of food allergy is a story about how
  the development of the immune system is tightly
  linked to the development of our digestive tract
  or as scientists and physicians usually refer to
  it our gut. A human being is born with an
  immature immune system and an immature gut and
  they grow up together. The immune system takes
  samples of gut contents and uses them to inform
  its understanding of the world--an understanding
  that helps safeguard the digestive system (and
  the body that houses it) against harmful
  microorganisms.
• The window for fine-tuning a babys mucosal
  immune system is relatively narrow starting when
  the infant is colonized with vaginal and
  intestinal bacteria from the mothers birth canal

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Terminology

• Allergic reactions are Antigen-Antibody reactions
• Antigen a foreign substance
• Antibody a protein produced in response to an
  antigen that is capable of binding specifically
  to the antigen!
• Haptens - a small molecule that has the ability
  to combine with an Ab or a cell-surface receptor.

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Our immune systems

• Immune cells are woven into the fabric of the gut
  than being restricted to one place but there are
  discrete structures for immune surveillance.
• Membrane cells (M-cells) recognize antigens and
  pass them to bone marrow cells (B-cells) Thymus
  cells ( T-cells) and antigen presenting cells
  (APC) such as macrophages and dendritic cells
• Activated B cells start producing antibodies

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Understanding Immunological concepts

• Food allergies are related to specific defenses
  or specific immunity
• Immune literary means free of burden
• Actions of the immune system are triggered by
  antigens (foreign substances).
• Most antigens are large protein molecules Some
  antigens are polysaccharides and few are
  glycoproteins (carbohydrate and protein) or
  nucleo-proteins.

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Understanding Immunological concepts

• Human body has two categories of defense system
• Non specific defenses
• Physical barriers (skin and mucous membrane)
• Chemical barriers (saliva mucus gastric juices
  etc)
• Cellular defenses (certain cells can eat
  invaders-phagocytes)
• Inflammation (reddening swelling and temperature
  increase of the affected sites)
• Fever (elevated body temperature)
• Molecular defenses (interferons or complementary
  system etc.)
• Specific defenses or specific immunity
• Antibodies (many kinds of antibodies for many
  kinds of antigens)

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Acquired-Active-Natural Specific Antibodies
(Immunoglobulins)

• There are five classes of Immunoglobulins
• 1) IgG Main class of antibodies in blood-also
  from mother-to-child (20)
• 2) IgA Small amount in blood but larger amount
  in tears milk saliva mucus and the lining
  tissues
• 3) IgM First Antibody secreted during the
  primary response
• 4) IgE (Reagin) Found mainly in body fluids
  and skin --- Associated with allergy reactions!
• 5) IgD Found in B-Cell membrane

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Who makes the immunoglobulin IgE
The allergen enters the body and is recognized by
sIg on a B-lymphocyte. The B-lymphocyte
proliferates and differentiates into plasma cells
that produce and secrete IgE against the allergen.
Picture credit used with permission from Dr.
Gary E. Kaiser http//www.cat.cc.md.us/courses/bio
141/lecguide/index.html
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Whats next
The next time the allergen enters the body it
cross-links the Fab portions of the IgE bound to
the mast cell. This triggers the mast cell to
degranulate that is release its histamine and
other inflammatory mediators.

• Picture credit used with permission from Dr.
  Gary E. Kaiser
• http//www.cat.cc.md.us/courses/bio141/lecguide/in
  dex.html

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Reasons of Symptoms

• When released from mast cells histamine causes
  vasodilation and an increase in permeability of
  blood vessel walls. These effects in turn cause
  the familiar symptoms of allergy including a
  runny nose and watering eyes. When released in
  the lungs histamine causes the airways to swell
  shut in an attempt to close the door on offending
  allergens and keep them out. Unfortunately the
  ultimate result of this response is the wheezing
  and difficulty in breathing seen in people with
  asthma - an occasionally deadly allergic
  complication which kills an estimated 4000
  Americans yearly.

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Hidden food ingredients in ready made food
products!

• Milk and milk product derivatives
• Egg and egg derivatives
• Peanuts tree nuts and derivatives
• Fish derivatives (surimi fish sauce fish paste
  etc)
• Soy and its derivatives

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To make the matter worse!

• Eating out is a nightmare
• African Chinese Indonesian Mexican Thai and
  Vietnamese dishes often contain peanuts. It is
  recommended that peanut-allergic individuals
  avoid these types of foods and restaurants.
• For traditional food restaurants
  cross-contamination of allergens to other foods
  can also a problem.

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Food Allergy Symptoms

• Allergic reactions to foods usually occur within
  minutes to a few hours after eating an offending
  food
• In very sensitive people even smelling or
  touching the offending food may produce an
  allergic reaction.
• Food allergies vary in their severity and how
  swiftly symptoms appear. The immediate
  life-threatening reactions experienced by some
  people (most often to peanuts) happen when the
  allergen binds to IgE-type antibodies which then
  trigger the release of histamine the compound
  responsible for acute inflammation with itching
  sneezing and other allergy symptoms

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Food Allergy Symptoms

• Food allergy reactions vary from person to
  person as well as within the same person
• The same food can produce totally different
  symptoms in different people as well as varying
  symptoms within the same person

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Symptoms-Food Allergy

• Nausea
• Diarrhea
• Abdominal cramps
• Pruritic rashes
• Angioedema
• Asthma/rhinitis
• Vomiting
• Hives
• Laryngeal edema
• Anaphylaxis

Exercise exacerbates symptoms
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Symptoms

• Nose Throat and Lung Reactions -Sneezing nasal
  congestion runny nose chronic cough shortness
  of breath or other breathing difficulties asthma
• Stomach and Intestinal Reactions -Nausea
  abdominal pain and bloating vomiting diarrhea
  cramping gas
• Skin - Swelling of lips mouth tongue face or
  throat hives rashes itching skin redness

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Anaphylaxis

• Different parts of the body experience food
  allergy reactions at the same time
• Reactions can progress rapidly and may include
  itching hives sweating swelling of the throat
  breathing difficulties lowered blood pressure
  unconsciousness and even death

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Severe Allergy Reactions

• Most food allergic reactions are mild but a
  small number of food-allergic individuals have
  severe reactions that can be life-threatening
• Anaphylaxis is rare but can be a possibly fatal
  food allergy reaction

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Have A Plan

• People who have severe allergic reactions need to
  plan for handling emergency situations
• May carry epinephrine for self-injection and
  warning medical alter bracelets or necklaces in
  case they become unconscious

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How to deal with food allergy!

• There is no specific antibody for any specific
  foods available!
• People who have food allergy need a total
  avoidance of the offending foods.
• Read food ingredient list.
• Eliminate cross-contamination during cooking and
  preparation!!!!

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Common medications prescribed by doctors

• epinephrine (relaxes smooth muscle constricts
  blood vessels and stimulates the heart used for
  severe systemic reactions)
• antihistamines (block the binding of histamine
  to histamine receptors on target cells)
• sodium cromolyn (prevents mast cells from
  releasing histamines).

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Living With A Food Allergy

• The only proven treatment for a food allergy is
  to avoid the offending food
• A elimination diet must be carefully developed
  and be personalized to take into account the
  ability of an individual to tolerate an allergic
  food

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Living With A Food Allergy

• Using an elimination diet for 1-2 years may
  promote outgrowing a food allergy
• Some food allergies particularly to peanuts
  nuts fish and shellfish can last a lifetime
• No drugs are available to treat food allergies

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Proper Diagnosis

• Elimination tests and food challenges should be
  conducted only under medical supervision
• ELISA and RAST are reliable tests for diagnosing
  allergies
• Cytotoxic testing and symptom provocation are
  unreliable methods

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RAST or ELISA

• Radioallergosorbent test (RAST) or enzyme-linked
  immunosorbent assay (ELISA) are reliable
  skin-prick testing and blood testing for
  diagnosing allergies.
• Two unreliable methods for diagnosing food
  allergies are cytotoxic testing and symptom
  provocation testing where a dose of the food
  extract is placed under the tongue or injected.

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How about food intolerance

• Direct effect of food
• Enzyme deficiency (e.g. lactase sucrase etc)
• Symptoms of food intolerance bloating cramping
  gas and diarrhea
• Main cause of food intolerance carbohydrates
  (lactose fructose sorbitol)
• True Allergy-Total avoidance necessary!
• Intolerance- Small amount may be tolerated

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Food allergy and biotechnology

• Although it is not easy to predict potential
  allergenicity of foods derived from GMO! there
  are some criteria to go by
• Sources of transferred genetic material While
  the crops from staple foods are derived contain
  tens of thousands of different proteins
  relatively few are allergenic.
• Synthesis of allergenic proteins also depends on
  the growing conditions and other stress factors.
• Molecular weight of most known allergens are
  between 10000 and 40000.

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Food allergy and biotechnology

• The amino acid sequence of many allergens is
  readily available.
• Labile allergens in foods that are eaten cooked
  or undergo other processing before consumption
  are of less concern.
• Most allergens are resistant to gastric acidity
  and to digestive proteases.
• New proteins expressed in non-edible portions of
  plants for example are not of a concern in terms
  of food allergy.

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Resources for food allergies

• Food Allergy and Anaphylaxis network (FAAN)
• Other resources