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Nutrition and Disease

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Title: Nutrition and Disease


1
EXAM 1
EXAM 2
Average 33.3
Average 36.1
2
Food Allergies
Lecture 24April 21, 2008Dr. QuadroFood
Science Department
3
Prevalence of 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.
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.

5
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.)

6
Basic 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.

7
  • 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)

8
  • Food allergies are 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.

9
Specific Immunity
Immunity
Ab Antibodies
Acquired
Innate (inborn) Genetic factors
Passive (Ready-made-Ab)
Active (own Ab)
Natural Maternal Ab
Artificial (Ab from Other sources)
Natural (Exposure to Foreign Agents)
Artificial (immunization)
10
Antibodies (Immunoglobulins)
  • Produces by B-linfocytes (bone marrow)
  • 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 Found mainly in body fluids and skin ---
    Associated with allergy reactions!
  • 5) IgD Found in B-Cell membrane

11
Antibody structure
Binding site for the antigen
Binding site for the receptor
12
(No Transcript)
13
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
14
Nature of IgE Allergic Reactions
Antigen IgE Mast cells Mediator
release Mediators histamine and others
Picture credit from Dr. Gary E.
Kaiser http//www.cat.cc.md.us/courses/bio141/lecg
uide/index.html
15
What does histamine do?
  • Vasodilation, increased capillary permeability,
    bronchoconstriction etc.

16
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

17
Lymphocytes
B lymphocytes mature in Bone marrow
and lymphatic tissue (spleen and lymph nodes) T
lymphocytes mature in the Thymus
18
T-lymphocytes
Mature in Thymus, which is most active just
before and after birth. The thymus starts to
shrink during puberty.
  • Helper T-Cells
  • Recognise antigens on surface of leukocytes,
    especially macrophages
  • Enlagre and form a clone of T-helper cells
  • Secrete interferon and cytokines which stimulate
    B-cells and stimulate killer -cells
  • Can be infected by HIV
  • Killer T-Cells
  • Also called cytotoxic
  • Destroy abnormal body cells, e.g. virus infected
    or cancer cells
  • Stimulated by cytokines (THcells)
  • Release perforin, which forms pores in target
    cells. This allows water and ions in lysis
  • Suppressor T-Cells
  • Control the immune system when the antigen
    /pathogen has
  • been destroyed
  • Only recently discovered so
  • little is known about them
  • Memory T-Cells
  • Can survive a long time and give lifelong
    immunity from infection
  • Can stimulate memory B-cells to produce
    antibodies
  • Can trigger production of killer T cells

19
How T-cells work
20
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)

21
Most common sites for allergic reactions
22
Symptoms-Food Allergy
  • Nausea
  • Diarrhea
  • Abdominal cramps
  • Pruritic rashes
  • Angioedema
  • Asthma/rhinitis
  • Vomiting
  • Hives
  • Laryngeal edema
  • Anaphylaxis

Exercise exacerbates symptoms
23
Anaphylaxis
  • Potential fatal reaction to a food allergen
    causing reduced oxygen supply to the heart and
    other body tissues.
  • Symptoms include difficult breathing, low blood
    pressure, pale skin, a weak rapid pulse, loss of
    consciousness, death.

24
Most common allergenic foods
  • Legumes (Peanuts and Soybeans)
  • Mollusks and shellfish (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

25
Children and Good Allergy
  • High prevalence in the first few years of life
  • Immature immune system and immature digestive
    system
  • Cows milk and soy, most common allergens
  • Breast feeding is recommended
  • Delay introduction of common allergenic foods
  • Sensitivity to most of the allergenic foods is
    usually lost by young children as they grow up

26
Cross-Reaction the reaction of one antigen with
antibodies developed against another antigen.
27
Cross-Reaction
28
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

29
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.

30
Solutions
  • People who have food allergy need a total
    avoidance of the offending foods.
  • Read food ingredient list.
  • Eliminate cross-contamination during cooking and
    preparation!!!!

31
Common prescribed medications
  • epinephrine (relaxes smooth muscle, constricts
    blood vessels, and stimulates the heart used for
    severe systemic reactions-anaphylaxis)
  • antihistamines (block the binding of histamine
    to histamine receptors on target cells)
  • sodium cromolyn (prevents mast cells from
    releasing histamines).

32
Other types of food allergy, Non-IgE Mediated
  • Immune Complex-mediated
  • Symptoms usually gastrointestinal
  • Delayed type hypersensitivity
  • Symptoms usually gastrointestinal

33
Food Aversion
  • A strong desire to avoid a particular food

Food Intolerance
Adverse reaction to food that does not involve
the immune system
34
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)

35
Allergy VS Intolerance
  • True Allergy-Total avoidance necessary!
  • Intolerance- Small amount may be tolerated

36
Diagnosis
  • Determine if the symptoms are mediated by the
    immune system

37
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

38
Diagnosis
  • Determine if the symptoms are mediated by the
    immune system
  • Complete physical
  • Detailed case history
  • Food diary
  • Positive identification of the allergen

39
Prick skin Test (PST)
  • Drop of the substance under test on the forearm
  • Allow a tiny amount to enter the skin (doctor
    pricks it with a needle)
  • After 15min, verify presence of bump

40
Radioallergosorbent Test (RAST)
  • Requires blood samples
  • Laboratory test are performed to look if the
    patients has IgE against specific types of food

41
Resources for food allergies
  • Food Allergy and Anaphylaxis network (FAAN)
  • American Academy of Allergy, Asthma and
    Immunology
  • American Dietetic Association
  • Asthma and Allergy Foundation
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