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.

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 IgENon-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 immunityImmune 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 ImmunityImmunity

Innate (inborn)Genetic factors

Acquired

Active(own An)

Passive(Ready-made-An)

Natural(Exposure toForeign Agents)

Artificial(immunization)

NaturalMaternal An

An = Antibodies

Artificial(An fromOther 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 releaseMediators= histamine and others

Picture credit: used with permission from Dr. Gary E. Kaiserhttp://www.cat.cc.md.us/courses/bio141/lecguide/index.html

Who makes the immunoglobulin IgE?

Picture credit: used with permission from Dr. Gary E. Kaiserhttp://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.

What’s next?

Picture credit: used with permission from Dr. Gary E. Kaiserhttp://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.

Nature of IgE Allergic Reactions

Antigen + IgE + Mast cells = Mediator releaseMediators= histamine and others

Picture credit: used with permission from Dr. Gary E. Kaiserhttp://www.cat.cc.md.us/courses/bio141/lecguide/index.html

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 antigenSecondary response: upon second exposure to the antigen, the Memory cells will divide, thus make more of the total antibody

Symptoms-Food Allergy*

NauseaDiarrheaAbdominal crampsPruritic rashesAngioedemaAsthma/rhinitis VomitingHivesLaryngeal edemaAnaphylaxis

* Exercise exacerbates symptoms

What are common allergenic foods?

Legumes (Peanuts and Soybeans)Mollusks (snails, mussels, oysters, scallops, clams, squid)MilkEggsFish (cod, salmon, haddock etc)Crustacea (shrimp, crawfish, lobster etc.)WheatTree 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 preservativesSulfites

Aspartame (a sweetener)- PKU

Monosodium glutamate

FD&C Yelow #5 (Tartrazine)

Cross-Reactions: Food and non-food allergens

Ragweed- Watermelon, cantaloupe, honeydew, bananasMugwort- celeryBirch pollen-carrots, apples, hazelnuts, potatoesBanana – 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. Kaiserhttp://www.cat.cc.md.us/courses/bio141/lecguide/index.html

Other types of food allergy, Non-IgE Mediated:

Immune Complex-mediatedSymptoms usually gastrointestinal

Delayed type hypersensitivitySymptoms usually gastrointestinal

How about food intolerance?

Direct effect of foodEnzyme deficiency (e.g., lactase, sucrase etc)Symptoms of food intolerance: bloating, cramping, gas and diarrheaMain 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-tyramine, phenylethylamine, cafiene – dose dependentIdiosyncratic 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!