Transcript chp 32 Krause

Chapter 32
Medical Nutrition
Therapy for Food
Allergy and Food
Intolerance
© 2004, 2002 Elsevier Inc. All rights reserved. © 2004, 2002 Elsevier Inc. All rights reserved.
Food Allergies—Cause
Algorithm content developed by John Anderson, PhD, and Sanford C. Garner, PhD, 2000.
© 2004, 2002 Elsevier Inc. All rights reserved.
Food Allergies—Pathophysiology
Algorithm content developed by John Anderson, PhD, and Sanford C. Garner, PhD, 2000.
© 2004, 2002 Elsevier Inc. All rights reserved.
Food Allergies—Medical and Nutritional
Management
Algorithm content developed by John Anderson, PhD, and Sanford C. Garner, PhD, 2000.
© 2004, 2002 Elsevier Inc. All rights reserved.
Key Terms

Adverse food reaction
—Any undesired response to a food regardless of
mechanism

Food allergy (hypersensitivity)
—Adverse food reaction that occurs consistently after
ingestion, inhalation, and/or touch of a particular food,
causing functional changes in target organs

Food intolerance
—Adverse reaction to a food caused by toxic,
pharmacologic, metabolic, or idiosyncratic reactions to
the food or chemical substances in the food
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Immune System

Humoral immunity
—Involves antibodies

Cellular immunity
—Involves the action of T lymphocytes
(T cells)
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Important Terms

Allergy

Allergens/antigen

Antibodies/immunoglobulins

B lymphocytes

T lymphocytes

Macrophages
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Types of Allergic Reactions

Type I—immediate hypersensitivity involves
IgE binding to the allergen

Type II—cytotoxic; not food related

Type III—a complex of the antigen and
antibody form; slow reaction

Type IV—T cells interact with the antigen as in
graft rejection
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Symptoms of Food Allergy
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Risk for Development of Food Allergy

Heredity

Exposure to a food (antigen)

Gastrointestinal permeability

Amount of antigen plus environmental
factors—exposure plus environment (pollen,
smoke, etc.)
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How Does a Reaction Occur?

Once a person becomes sensitized,
ingestion of milligram quantities of
food allergens may be enough to trigger
an allergic reaction.

After IgE antibodies are produced, they
circulate in the blood and bind to the
surface of body cells called “mast
cells.” This triggers a complex series of
reactions.
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How Does a Reaction Occur?—cont’d

Release of histamine and other mediators
occurs rapidly, within 5 minutes after the
interaction between the allergen and the IgE
antibody on the surface of the mast cell.

Once released, they enter the bloodstream and
bind to “receptors” on other cells.

The severity of the allergic reaction to a food
depends primarily on how sensitized the person
is and the amount of allergenic food that was
eaten.
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How Does a Reaction Occur?—cont’d

Food-sensitive people who have
experienced more than one allergic
reaction usually report the same early
warning signs and symptoms with each
reaction.

Treatment of food-induced allergic
reactions is directed at several points in the
series of events.
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Concerns for Infants and Young Children

In studies of the incidence of cow’s milk,
protein allergy in infancy has been estimated at
about 2% to 3%.

Allergic reactions are also frequently observed
against egg white, fish, cereals, nuts, peanuts,
and soybeans that are found in breast milk.
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Concerns for Infants and Young Children
—cont’d

Exclusive breast-feeding with
exclusion of cow’s milk formulas and
complementary foods during the first
4 to 6 months has a preventive effect
against allergic symptoms, extending
beyond the period of breast-feeding.

Formulas based on soy protein are
not recommended for the prevention
of food allergy.
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Concerns for Infants and Young Children
—cont’d

Breast-fed infants who have developed
allergy to cow’s milk are shown to have been
given cow’s milk formula in the nursery
shortly after birth, prior to starting breastfeeding.

This early “bottle” of cow’s milk formula
may have led to initial sensitization to cow’s
milk
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Symptoms of Food Allergies

Gastrointestinal manifestations

Cutaneous manifestations

Respiratory manifestations

Systemic manifestations

Controversial or unproven
manifestations
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Do Fruits and Vegetables Cause Reactions?
Role of Oral Allergy Syndrome

Oral allergy syndrome (OAS)—caused by
cross-reacting or identical allergens that are
present in both the pollen and fresh food

Symptoms—itching or swelling of the lips,
tongue, throat, or roof of the mouth. They are
less severe if the individual is receiving regular
doses of antihistamines.
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Foods Associated with Oral Allergy
Syndrome

Vegetables—carrots, celery, parsley,
potato, tomato

Seeds and nuts—fennel seed, hazelnut
(filbert), sunflower seeds

Fruits—apple, apricot, banana,
cantaloupe, cherry, honeydew, orange,
peach, pear, watermelon
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Treatment of Oral Allergy Syndrome

Not much is known, but some researchers
report that both hay fever symptoms and OAS
symptoms go away if the affected person
receives immunotherapy injections with
extracts of cross-reacting pollens.
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Symptoms of Milk-Allergic Children

Hives and itching (skin)

Wheezing

Coughing

Severe nasal symptoms (respiratory tract)

Vomiting and/or diarrhea (gastrointestinal tract)
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Atopic Eczema
Fig. p. .
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Growing Out of Food Allergies

Approximately 85% of young children with
allergies become tolerant of the foods by age 3.

It is rare to find these allergies in adults.

Allergies to peanuts, tree nuts, fish, and
shellfish are not easily outgrown.
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Diagnosis

History—family history, early feeding
history

Physical examination—malnutrition,
eczema, rhinitis, asthma

Biochemical testing—R/O other conditions

Food elimination—confirm a food allergy

Food challenge—once symptom free,
reintroduce one food at a time
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Diagnosis—cont’d
Food and symptom diary
—Quantity
—Time from ingestion to symptoms
—Symptoms
—Symptoms every time food ingested
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Diagnostic Tests

Immunologic testing
—Skin-prick
—RAST: radioallergosorbent test
—ELISA: enzyme-linked immunosorbent assay
—FEIA
—Cytotoxic testing
—Sublingual testing
—Provocation testing and neutralization
—Kinesiologic testing
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Skin-Prick Test
Fig. . p. .
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Treatment

Elimination diet
—Investigational short-term or possible
lifelong eating plan that omits one or more
foods suspected or known to cause an
adverse food reaction or allergic response
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Treatment—cont’d

Avoid the food

Nutritional counseling
—Hidden forms of the food
—Replace nutrients missing

Retest for allergy every 1 to 3 months
(children grow out of the allergies)
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Treatment—cont’d

Careful food selection for common allergies

Infants
—Breast milk (mother avoids allergenic
foods and foods that cause infant
gastrointestinal distress)
—Cow’s milk allergy infants need casein
hydrosylate formula rather than soy.
—Goat’s milk is not usually a good choice.
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Reasons That Allergens May Contaminate
a Food

Same utensils used to serve different foods

Same equipment used to manufacture different
foods

Misleading labels

Ingredients listed in terms of purpose instead of
ingredient

Addition of allergenic product to second
product that bears a label only listing
ingredients of second product (mayonnaise)
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Strategies for Coping with Food
Allergy
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Strategies for Coping with Food Allergy —cont’d
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Foods Known to Cross-React in Latex Allergy
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Development of New Allergies

The development of a specific food allergy
depends upon prior exposure to that food.

It is uncertain how and why adults can, for no
apparent reason, develop an allergy to a food
eaten many times before.

It is also uncertain if these reactions will lessen
or disappear over time.
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Migraines

Females are greater than 3 times more
likely to experience migraines than
males.

People of both sexes who suffer from
migraines are much more likely than
those who do not to report food
allergies
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Colic

Sleeplessness and irritability

Not usually an allergy
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Food Intolerances

Additives

Sulfites

Lactose
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Food Labeling

The US Food and Drug Administration
(FDA) is striving to improve labeling of
snack foods that contain allergens.

A study found undisclosed traces of
peanuts in a quarter of all snacks tested.

Such trace amounts may be due to cross
contamination, in which utensils used in
making one product are used in another.
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Additives

Food and food additive allergies:
—Egg allergy and its potential crossreaction with the influenza vaccine
—Peanut and tree nut allergies

An awareness of these issues will help
primary providers identify these
patients earlier, thereby avoiding
repeated ingestion of these allergens.
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Regulations

Tighter regulations may be forthcoming.

It’s unlikely that the FDA will be able to inspect al
food manufacturers to enforce such rules.

The administration is issuing new guidelines to its
investigators to help them pinpoint and tackle
problem manufacturers.
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Prevention
In high-risk infants

Mother should breast-feed and avoid
typically allergenic foods.

Wait until 2 to 3 yrs of age to introduce
milk, egg, peanuts, fish.
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