Food Allergies

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Food Allergies
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Outlines

• Statistics
• What is food allergy?
• Immunology concepts
• What foods causes allergies?
• Possible ways to deal with food allergy
• Resources for food allergies

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How prevalence is food allergy?

• Experts agree that allergies in developed
  countries are becoming more common.
• In the U.S., food allergies afflict 2-2.5 adults
  and 6-8 children.
• 100-175 people in the U.S. die each year.
• Death generally result from anaphylactic shock,
  often to peanuts or tree nuts.
• More than 160 foods have been associated with
  allergic reactions.

CEN/January 7, 2002 page 21.
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What is food allergy?

• Food allergy is an inappropriate immune response
  to an otherwise harmless food.
• True food allergy involves several types of
  immunological responses.
• Food allergens are usually proteins.
• Some foods may contain haptens or haptens
  carrier. (A hepten- a small molecule that has the
  ability to combine with an antibody (Ab) or a
  cell-surface receptor e.g. poison ivy)

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Understanding Immunological concepts

• Human body has many defense mechanisms to fight
  off infectious diseases and other toxic foreign
  substances.
• Strong healthy adult human can fight off most of
  infectious diseases.
• Ability to fight off disease can be modulated by
  genetics, age, race and lifestyles (diets,
  exercise and amount of sleep etc.)

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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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Types of food allergies

• Immediate hypersensitivity with IgE which occurs
  within minutes to a few hours after ingestion of
  offending foods.
• Systemic Itching, urticaria (hives), Vomiting,
  Abdominal cramps, diarrhea and respiratory
  distress, and in severe cases anaphylactic shock
• Localized hives and eczema or atopy (an umbrella
  term covering clinical presentations of food
  allergy etc)
• Delayed hypersensitivity reactions (gt8hours after
  ingestion) cellular immunity involving
  T-lymphocytes and macrophages

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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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Stages of food allergyor hypersensitivity

• A. Sensitization initial meeting of an allergen
  and the immune system that results in IgE
  production!
• B. Activation of mast cells
• IgE
• Non-IgE substances (eg. Drugs)

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Understanding Immunological concepts

• Food allergies is 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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Specific Immunity
Immunity
An Antibodies
Acquired
Innate (inborn) Genetic factors
Passive (Ready-made-An)
Active (own An)
Natural Maternal An
Artificial (An from Other sources)
Natural (Exposure to Foreign Agents)
Artificial (immunization)
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What are 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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Nature of IgE Allergic Reactions
Antigen IgE Mast cells Mediator
release Mediators histamine and others
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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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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Nature of IgE Allergic Reactions
Antigen IgE Mast cells Mediator
release Mediators histamine and others
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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What does histamine do?

• Vasodilation
• Increased capillary permeability
• Bronchoconstriction

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Primary and secondary responses to an antigen
Primary response first response when hosts
B-cell recognize the antigen
Secondary response upon second exposure to the
antigen, the Memory cells will divide, thus make
more of the total antibody
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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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What are common allergenic foods?

• Legumes (Peanuts and Soybeans)
• Mollusks (snails, mussels, oysters, scallops,
  clams, squid)
• Milk
• Eggs
• Fish (cod, salmon, haddock etc)
• Crustacea (shrimp, crawfish, lobster etc.)
• Wheat
• Tree nuts (almonds, walnuts, Brazil nuts etc)
• Selected food additives

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Itsnot easyliving with food allergies!
What would you choose to eat, if you are
allergic to milk or dairy products?
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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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What about food Additives?

• Sulfur-based preservatives
• Sulfites
• Aspartame (a sweetener)- PKU
• Monosodium glutamate
• FDC Yelow 5 (Tartrazine)

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Cross-Reactions Food and non-food allergens

• Ragweed, watermelon, cantaloupe, honeydew,
  bananas
• Mugwort- celery
• Birch pollen-carrots, apples, hazelnuts, potatoes
• Banana latex
• If allergic to one shellfish or legumes, likely
  allergic to all!

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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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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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Other types of food allergy, Non-IgE Mediated

• Immune Complex-mediated
• Symptoms usually gastrointestinal
• Delayed type hypersensitivity
• Symptoms usually gastrointestinal

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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)

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What about Allergy VS Intolerance!

• True Allergy-Total avoidance necessary!
• Intolerance- Small amount may be tolerated

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Other causes of allergy-like food problems

• Microbial products- e.g. histamine Some food
  products have high levels of histamine (eg
  fermented foods)
• Pharmacological reaction-tyramine,
  phenylethylamine, caffeine dose dependent
• Idiosyncratic reactions (adverse reactions of
  drugs etc dose dependent)
• Psychological disorders

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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 which 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 10,000 and 40,000.

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Food allergies 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
• See handouts

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Questions?