Food Allergies 101
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Food Allergies 101






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    Food Allergies 101 Food Allergies 101 Presentation Transcript

    • 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
      • Resources for food allergies
    • 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.
    • 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.)
    • 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
    • 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)
    • 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.)
    • 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.
    • 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)
    • 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 .
    • Specific Immunity Immunity Innate (inborn) Genetic factors Acquired Active (own An) Passive (Ready-made-An) Natural (Exposure to Foreign Agents) Artificial (immunization) Natural Maternal An An = Antibodies Artificial (An from Other sources)
    • 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
    • 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
    • Who makes the immunoglobulin IgE? Picture credit: used with permission from Dr. Gary E. Kaiser 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.
    • What’s next?
      • Picture credit: used with permission from Dr. Gary E. Kaiser
      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.
    • 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
    • What does histamine do?
      • Vasodilation, increased capillary permeability, bronchoconstriction etc.
    • 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
    • Symptoms-Food Allergy*
      • Nausea
      • Diarrhea
      • Abdominal cramps
      • Pruritic rashes
      • Angioedema
      • Asthma/rhinitis
      • Vomiting
      • Hives
      • Laryngeal edema
      • Anaphylaxis
      * Exercise exacerbates symptoms
    • 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
    • It is not easy…living with food allergies! What would you choose to eat, if you are allergic to milk or dairy products?
    • 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
    • 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
      • 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!
      • 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.
    • 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!!!!
    • 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.. Picture credit: used with permission from Dr. Gary E. Kaiser
    • Other types of food allergy, Non-IgE Mediated:
      • Immune Complex-mediated
          • Symptoms usually gastrointestinal
      • Delayed type hypersensitivity
          • Symptoms usually gastrointestinal
    • 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!
      • True Allergy-Total avoidance necessary!
      • Intolerance- Small amount may be tolerated
    • 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-tyr amine , phenylethyl amine , cafiene – dose dependent
      • Idiosyncratic reactions – (adverse reactions of drugs etc – dose dependent)
      • Psychological disorders
    • 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.
    • 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.
    • Resources for food allergies
      • Food Allergy and Anaphylaxis network (FAAN)
      • Other resources
      • See handouts
    • I will be glad to entertain any question!