Food Allergies 101
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  • 1. Food Allergies…101 Amy Simonne, Ph.D. Assistant Professor FYCS University of Florida Food, Nutrition and Health Update 2002, Feb 12, 2002
  • 2. Outlines
    • Statistics
    • What is food allergy
    • Immunology concepts
    • What foods causes allergies
    • Possible ways to deal with food allergy
    • Resources for food allergies
  • 3. 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.
  • 4. 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.)
  • 5. 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
  • 6. 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)
  • 7.  
  • 8. 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.)
  • 9. 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.
  • 10. 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)
  • 11. 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 .
  • 12. 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)
  • 13. 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
  • 14. 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
  • 15. Who makes the immunoglobulin IgE? Picture credit: used with permission from Dr. Gary E. Kaiser http://www.cat.cc.md.us/courses/bio141/lecguide/index.html 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.
  • 16. What’s next?
    • Picture credit: used with permission from Dr. Gary E. Kaiser
    • http://www.cat.cc.md.us/courses/bio141/lecguide/index.html
    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.
  • 17. 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
  • 18. What does histamine do?
    • Vasodilation, increased capillary permeability, bronchoconstriction etc.
  • 19. 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
  • 20.  
  • 21. Symptoms-Food Allergy*
    • Nausea
    • Diarrhea
    • Abdominal cramps
    • Pruritic rashes
    • Angioedema
    • Asthma/rhinitis
    • Vomiting
    • Hives
    • Laryngeal edema
    • Anaphylaxis
    * Exercise exacerbates symptoms
  • 22. 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
  • 23. It is not easy…living with food allergies! What would you choose to eat, if you are allergic to milk or dairy products?
  • 24. 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
  • 25. What about food Additives?
    • Sulfur-based preservatives
        • Sulfites
    • Aspartame (a sweetener)- PKU
    • Monosodium glutamate
    • FD&C Yelow #5 (Tartrazine)
  • 26. 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!
  • 27. 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.
  • 28. 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!!!!
  • 29. 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).
  • 30. 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
  • 31. Other types of food allergy, Non-IgE Mediated:
    • Immune Complex-mediated
        • Symptoms usually gastrointestinal
    • Delayed type hypersensitivity
        • Symptoms usually gastrointestinal
  • 32. 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)
  • 33. What about Allergy VS Intolerance!
    • True Allergy-Total avoidance necessary!
    • Intolerance- Small amount may be tolerated
  • 34. 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
  • 35. 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.
  • 36. 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.
  • 37. Resources for food allergies
    • Food Allergy and Anaphylaxis network (FAAN)
    • Other resources
    • See handouts
  • 38. I will be glad to entertain any question!