Food allergies 101
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Food Allergies…101. Amy Simonne, Ph.D. Assistant Professor FYCS University of Florida. Food, Nutrition and Health Update 2002, Feb 12, 2002. Outlines. Statistics What is food allergy Immunology concepts What foods causes allergies Possible ways to deal with food allergy

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Food allergies 101 l.jpg

Food Allergies…101

Amy Simonne, Ph.D.

Assistant Professor

FYCS

University of Florida

Food, Nutrition and Health Update 2002, Feb 12, 2002


Outlines l.jpg
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.

C&EN/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 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 (>8hours after ingestion): cellular immunity involving T-lymphocytes and macrophages


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What are stages of food allergy or 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

  • 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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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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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/bio141/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/bio141/lecguide/index.html


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What’s 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/index.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/bio141/lecguide/index.html


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What does histamine do?

  • Vasodilation, increased capillary permeability, bronchoconstriction etc.


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Primary and secondary responses to an antigen

Primary response: first response when host’s 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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It is not easy…living 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

  • FD&C Yelow #5 (Tartrazine)


  • Cross reactions food and non food allergens l.jpg
    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!


    To make the matter worse l.jpg
    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).


    If antidose is given l.jpg
    If antidose is given..

    Picture credit: used with permission from Dr. Gary E. Kaiser

    http://www.cat.cc.md.us/courses/bio141/lecguide/index.html


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    Other types of food allergy, Non-IgE Mediated:

    • Immune Complex-mediated

      • Symptoms usually gastrointestinal

  • Delayed type hypersensitivity

    • Symptoms usually gastrointestinal


  • How about food intolerance l.jpg
    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)


    What about allergy vs intolerance l.jpg
    What about Allergy VS Intolerance!

    • True Allergy-Total avoidance necessary!

    • Intolerance- Small amount may be tolerated


    Other causes of allergy like food problems l.jpg
    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, cafiene – dose dependent

    • Idiosyncratic reactions – (adverse reactions of drugs etc – dose dependent)

    • Psychological disorders


    Food allergy and biotechnology l.jpg
    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 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

    • See handouts