Download egg whites and autoimmune disease

EGG WHITES AND
AUTOIMMUNE DISEASE
LOREN CORDAIN, PH.D.
EGG WHITES AND AUTOIMMUNE DISEASE
By Loren Cordain, Ph.D., Professsor
eggs are uniquely different from meats in that they
represent the reproductive endpoints of adult birds
which exist outside their mother’s body in a semi
permeable, warm compartment. As such, all eggs
are particularly vulnerable to invasion, attack and
destruction by microorganisms such as fungi, bacteria
and viruses present in their nesting environment.
In all three of my books, I have advocated egg
consumption, particularly eggs that are produced with
high omega 3 fatty acid contents. Chicken eggs are
generally a nutritious food and are a good source of
selenium, vitamin A, vitamin D and the B vitamins
and some minerals. Additionally, numerous recent
experimental and epidemiological studies (reviewed in
references 1, 2) indicate that regular egg consumption
(7 per week) does not increase the risk for coronary
heart disease (CHD). As I have previously noted,
although eggs are one of the most concentrated
sources of dietary cholesterol (212 mg per egg), dietary
cholesterol has a minimal effect upon blood cholesterol
concentrations in most people.1, 3 Further, high
cholesterol egg diets cause an increase in blood HDL
particles (the good particles that remove cholesterol
from the body)1 and reduce the highly atherogenic
small dense LDL particles while simultaneously
increasing the less atherogenic large, “fluffy” LDL
particles.4, 5
Figure 1. Anatomy of a chicken egg.
Vitelline
Membrane
So, should everybody include eggs in their diet on a
daily basis? Not necessarily, particularly if we examine
the evolutionary template. Without question our
pre- agricultural ancestors would have collected and
consumed eggs from birds’ nests whenever possible.
However, in the wild, bird eggs only appear seasonally.
Hence, pre-agricultural humans could have never
consumed two eggs for breakfast every morning of the
year similar to some westernized people, but rather
only occasionally for a few brief weeks or months.
Yolk
Albumen
(white)
Chalazae
If we follow up on the clue from the evolutionary
template and examine eggs more closely, they
maintain certain nutritional shortcomings that may
be problematic, particularly for people suffering from
autoimmune diseases and allergies. Although eggs
are classified as animal food sources and are lumped
together with meats in the USDA My Pyramid,
Air Cell
Outer Membrane
Inner Membrane
2
So, from a nutritional perspective, egg white appears
to be a healthful protein source with an amino acid
composition capable of stimulating rapid muscular
growth. As is almost always the case in nutrition
and medicine, the devil lies in the detail, and a closer
examination of egg white reveals that it is a complex
mixture of more than 40 proteins, some of which may
adversely affect human health.6-8
The innermost yolk represents the growing embryo
which is anchored to the albumen or egg white by
structures called chalazae. Outward from the egg
white are the inner and outer membranes and then
the shell, all of which provide physical barriers to
infection from pathogens and microorganisms. The
egg white makes up about 58% of the total egg volume
and contains about 50% of the total egg protein
and is composed of 88.5% water, 10.5% protein and
0.5% carbohydrate6. The function of the egg white
is threefold: 1) storage of nutrients for the growing
embryo (yolk), 2) protection of the egg from microbial
attack, and 3) transport of nutrients into the growing
embryo.
A chicken egg is the reproductive endpoint for adult
birds and survives by living outside its mother’s body
in a semi permeable compartment that is essentially
immovable. Accordingly, it has no means of protecting
itself from microorganisms or predation by physical
escape or avoidance. For this reason, the evolutionary
strategy eggs have taken to protect themselves from
microbial invaders is to select for toxic substances in
the egg white; mainly in the form of antimicrobial
proteins. Table 2 lists the major proteins in egg
whites and their likely functions. Note that except for
ovalbumen which comprises 54% of the total protein
in egg white, virtually all the other major proteins
Most nutritionists and dieticians consider egg white
to be one of the most healthful and complete dietary
proteins because its amino acid composition promotes
rapid growth in laboratory animals. Athletes and
body builders frequently consume huge quantities of
dried egg white for its high concentrations of muscle
stimulating branch chain amino acids (Table 1).
Table 1. Branch chain amino acid (BCCA) content in egg white and other food sources.
1000 kcal sample Weight of sample (grams) Isoleucine (mg)
Leucine (mg)
Valine (mg)
Total BCCA (mg)
Dried Egg White 26212002179151352943446
(84% protein)
Egg white raw200011880177401340043020
Whey Protein (80 % Protein)
250
9225
17192
8968
35385
Whey Protein (75 % Protein)
250
8812
16425
8570
33807
Meats (n=4)6364928314741967133695
Soy Protein (70% Protein)
301886414815923232911
Seafoods (n=20)744312852803128326
Hard boiled egg64538974426494813271
Milk (n=1)162832395240358112060
Beans (n=8)31995249349111939
Veggies (n=18)2383287924507712
Grains (n=8)1305303417276066
Nuts & Seeds (n=10)1119198014914590
Starcy Root Vegetables (n=6)4506625801692
Fruits (n=20)209319292820
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dissolving bacterial cell walls.13 Lysozyme is unusual
among the major egg white proteins in that it has an
alkaline isoelectric point (pI), which means that it can
form strong complexes with other egg white proteins
including ovomucin, ovalbumen and
ovotransferrin.6, 13 Hence, even though lysozyme is
a benign enzyme produced in our own bodies, when
we eat egg white lysozyme, it comes as a compound
attached to other egg white proteins foreign to our
bodies.
(~33% of the total) maintain one form or another of
antimicrobial activity.
Egg white allergy in the general population varies
between 1.6 – 3.2 % and is the second most common
cause of food allergy in children next to milk8 (Table
3). In children, egg allergy usually develops within
the first two years of life and resolves itself by school
age.8 For both adults and children one or more of
the following symptoms may occur: hives, atopic
dermatitis (red, flaky itchy skin), asthma, runny nose,
diarrhea, abdominal pain, rapid swelling of the skin
and mucosa, and anaphylactic shock which may be
life threatening. The major allergens in egg white are
ovomucoid, ovalbumen, ovotransferrin and lysozymes8
(Table 2). So for the vast majority of children and
adults (98.4 – 96.8 % of the population), egg white
allergy is not a problem, and except for anaphylactic
shock is not a debilitating or life threatening condition.
In the human digestive tract, enzymes called proteases
normally break down proteins into their constituent
amino acids so that the amino acids can be absorbed
across the intestines. Because egg white protein
contains high concentrations of protease inhibitors
(ovomucoid, ovoinhibitor, ovostatin, cystatin) (Table
2), the human gut proteases (trypsin and chymotrypsin
primarily) are less effective in degrading egg white
proteins, and lysozyme/egg white protein complexes.
Additionally lysozyme is stable in the acidic gut
environment13 and therefore arrives intact in the lower
gastrointestinal tract.
The same conclusion may not be true for people
suffering from an autoimmune disease multiple
sclerosis, rheumatoid arthritis, ankylosing spondylitis,
lupus erythematosus and others), since egg white
consumption may contribute to the origin and
progression of these diseases via a process of molecular
mimicry that I have previously outlined for dietary
lectins found in wheat, peanuts and other grains and
legumes.12
So what’s wrong if lysozyme/egg white protein
complexes aren’t dissolved by normal digestive
processes? Normally, large multifaceted proteins
such as these complexes don’t have a prayer of getting
across the intestinal barrier and into the bloodstream
where they can interact with the immune system.
Once again, lysozyme is an unusual protein because
it rapidly breeches the gut barrier and enters human
circulation14. Lysozyme and the complexes it forms
with other egg white proteins can cross the gut
barrier since lysozyme contains a sugar15,16 that
specifically binds a gut receptor, the epidermal growth
factor receptor (EGF-R) which allows these protein
complexes to enter circulation. Remember that
lysozyme also binds gut bacterial cell walls, so that
these peptides also can gain access to circulation via
this Trojan Horse mechanism.
You can see from Table 2 that egg white protein is no
simple protein, but rather a conglomeration of multiple
proteins which have been designed by natural selection
to cause toxic and lethal effects in bacteria and
microorganisms reminiscent of food lectins found in
grains and legumes.12 In order for any food proteins to
potentially cause or promote an autoimmune disease, it
must:
1. Survive the human digestive processes intact
2. Cross the gut barrier intact either alone or
with other attached proteins
3. Interact with the immune system in a
manner suspected of causing an autoimmune
disease.
A number of egg white proteins fulfill these necessary
steps. Most problematic is the egg white protein,
lysozyme which is actually an enzyme known as
N- acetylhexosaminodase that is also found in many
human tissues, including tears.13 The function of
lysozyme in both egg whites and in human tears is
to act as a potent bacterialcidal agent by binding and
4
Table 2. Major proteins and their properties found in egg whites.6-10
Protein
% total proteins
Function(s)
Ovalbumen54Storage protein
Ovotransferrin
12
Iron binding with antimicrobial activity
Ovomucoid11Protease inhibitor/antimicrobial activity?
Ovomucin3.5Potent antiviral activity
Lysozyme3.4Antibacterial activity
G2 globulin4.0?Antibacterial activity
G3 globulin4.0?Antibacterial activity
Ovoinhibitor1.5Protease inhibitor/antimicrobial activity?
Ovoglycoprotein1.0?
Thiamin binding protein
1.0
Thiamin transport
Ovoflavoprotein/Riboflavin0.8Riboflavin transport
binding protein
Ovomacroglobulin (Ovostatin)
0.5
Protease inhibitor/antimicrobial activity?
Cystatin0.05Protease inhibitor/antimicrobial activity?
Avidin0.05Antimicrobial activity
Total88.8
Once the (lysozyme/egg white protein/bacterial cell
wall protein) complex gains access to circulation, it
has the potential to activate the immune system in
a process called three way molecular mimicry.12 In
genetically susceptible individuals, this process causes
the immune system to lose the ability to recognize self
proteins from foreign proteins in such a manner that
the immune system ultimately destroys the body’s own
tissues.
Bottom line: If you suffer from an autoimmune
disease such as multiple sclerosis, rheumatoid arthritis
or others, I have previously recommended that you
adopt a grain, dairy and legume free diet. To that
list, you may also want to add eggs for the reasons I
have described above. Eliminate all of these foods
for an extended period and carefully monitor your
symptoms. You may want to then gradually add single
foods back into your diet to see if they cause problems
to re-appear.
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Figure 2. Bacterial/Egg Peptides.
B/E
B/E
LYSO
Bacterial/Egg Peptides
B/E
Lysozyme
LYSO
Gut Interior
EGF-R EGF-R
O
LYS
Enterocyte
Cytosol
B/E
F-R
EG
Into
Lymph
B/E
LYSO
Into
Circulation
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Activate
T-Cells
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