Food allergies are due to IgE antibodies made
for specific foods that an individual has for some reason developed
because their body has misinterpreted the food(s) as a foreign invading
protein. The presence of IgE antibody to the specific food a person is
allergic to results in an immediate immune reaction of the body to the
food when it is eaten. The IgE antibody binds its specific food protein
and initiates reactions in the body that include the release of chemicals
such as histamine that may result in symptoms of itching, swelling,
wheezing or difficulty breathing, rash or hives, and if severe, shock
resulting in death if not reversed. Vomiting and diarrhea may occur but
are less common. Testing for the presence of allergy to a food or foods
can be done by blood test or skin testing or both. One of the most common
blood tests is the RAST test that looks for the presence of the specific
IgE antibodies to common food allergens and other foods based on a history
suggesting that a particular food is suspect. Skin testing is done by
injecting or applying extracts of the common and any suspect food(s) to
pricked or scratched skin and looking for diagnostic “hive” like reactions
at the site of the suspect food. The most common food allergens are
peanut, cow’s milk, wheat, corn, soy, shellfish, eggs, tree nuts,
chocolate, pork, tomato, and citrus.
The terms food intolerance and sensitivity are commonly used
interchangeably. They refer to a group of food reactions that occur that
are not IgE antibody caused. In more general terms they refer to any
adverse or unpleasant reaction that occurs after a food is eaten.
Food reactions that are not allergic in cause may have a variety of
causes. A particular food may not be tolerated because it is not digested
adequately due to an enzyme deficiency. Lactase, the enzyme that digests
milk sugar or lactose, is present on the surface of the intestine lining
cells. Lactase deficiency can be inherited or acquired. It commonly occurs
whenever the intestine lining is damaged. Because the lactase enzymes are
on the outer most surface of the intestine they are more vulnerable to
injury. For example, after intestinal flu or in untreated Celiac disease,
lactose intolerance is common. Other sugar enzymes can be deficient or the
intestine can be simply overwhelmed by too large a sugar load at one time.
A classic example is “the Big Gulp” syndrome when someone drinks a giant
cola beverage then experiences the “gut ache” from the tremendous amount
of fructose. Large amounts cannot be handled by the intestine and that
results in bloating, urgency and terrible diarrhea.
Deficiency of digestive enzymes released into the intestine can result
in poor digestion of foods. For example, when the pancreas gland is
damaged (pancreatitis) chronically, usually from chronic alcohol abuse, or
is congenitally underdeveloped or malfunctioning (e.g. cystic fibrosis).
The pancreatic enzyme deficiency that occurs results in malabsorption,
especially for fats, that cause symptoms of diarrhea and weight loss.
Abnormal bacteria types and levels in the gut, also known as dysbiosis,
and abnormal excess levels of “bad” bacteria or presence of bacteria in
upper small intestine where little or no bacteria normally occur
(bacterial overgrowth) can interfere with digestion, absorption or cause
fermentation of food resulting in symptoms of abdominal pain, bloating,
gas, and diarrhea.
Some foods and food additives have a direct toxic effect on the
gastrointestinal tract. Additives such as MSG and sulfites can cause
symptoms, including flushing and diarrhea or the “Chinese restaurant” or
“salad bar” syndromes.
All foods contain proteins known as lectins. Some of these proteins are
highly resistant to digestion and are toxic to the human intestine
especially if they are not pre-treated by soaking, cooking well, or
removing toxic portions. For example, inadequately soaked and cooked
kidney beans will cause a food poisoning like illness. There are several
foods that have lectins that are poorly tolerated by many humans and are
lethal to insects and pests. One researcher, Loren Cordain PhD., author of
the Paleo Diet, has published extensive research on how the human
intestine is not “evolved” to tolerate many of the foods we now eat but
did not eat in the ancient “hunter-gatherer” times resulting in many of
the illness seen in modern societies and the rising epidemic of autoimmune
diseases. Several of the “modern” foods that were not part of the ancient
diet but constitute much our diet now have well recognized toxic or poorly
tolerated proteins known as lectins. Examples include wheat germ
agglutinin (WGA), casein (cow’s milk protein), peanut agglutinin (PNA),
soyabean agglutinin (SBA) and tomato lectin (TL) that have been shown in
animal studies to be toxic to the human gut. There are a few published
studies and little active research on the role of dietary lectins in
health and disease.
When the reaction is an immune toxicity reaction to a food protein
intestinal damage commonly results, frequently referred to as “leaky gut”
because of the symptoms of malabsorption or the entry of toxic food
proteins and/or bacterial products into the blood stream resulting in a
variety of adverse health effects. This reaction may result in
autoimmunity, the body attacking itself within the gut or distant organs
or tissues. The reaction may be aided by abnormal bacteria types and/or
levels in the gut (dysbiosis). The symptoms commonly develop over time and
flare in just hours to up to three days after eating the offending food
and continue as the food is eaten.
Because the protein in the food is usually the cause and such proteins
may be hidden in other foods, especially processed foods, and the toxicity
is more of a delayed and cumulative immune reaction, it is very difficult
for the person suffering from this to identify the specific food as the
cause. For example gluten (the protein in wheat) and casein (the protein
in cow’s milk) are in many foods and toxic to many individuals. Over time
people sensitive to such food proteins typically become more ill and may
develop enough intestinal injury that blood tests for other types of
antibodies, IgG and/or IgA, to the food or specific food proteins, may be
detectable in the blood, stool or saliva.
Delayed immune response to proteins in the food (wheat, cow’s milk)
resulting in bowel injury, gastrointestinal and non-gastrointestinal
symptoms and increased autoimmune conditions is most well recognized in
Celiac disease. It is an autoimmune disease resulting from ingestion of
gluten in wheat or products made from wheat flour (or gluten like proteins
in barley and rye). It used to be considered a disease of children and
rare, especially in the United States. However, blood test screening
studies have documented that it is present in approximately 1 in 133 to 1
in100 people worldwide though most of those affected are undiagnosed and
untreated. It is diagnosed by positive screening blood tests and confirmed
by a characteristic abnormal small intestine on biopsy followed by relief
of symptoms and return of the intestine to normal after a gluten-free
diet. Untreated it is associated with higher rates of cancer especially
lymphoma, osteoporosis, anemia, and other complications of malabsorption
resulting in shortened life expectancy. It is treated with a life-long
gluten free-diet. Lesser degrees of gluten intolerance or sensitivity may
not be severe enough to cause abnormal or diagnostic blood tests and
intestinal biopsies but result in symptoms that improve or resolve with a
gluten-free diet and may be detected by elevated stool or saliva antibody
tests.
Though injury to the intestine tissue may be seen visually as abnormal
appearing tissue during endoscopic procedures such findings are
non-specific for the cause. The tissue frequently appears normal and
therefore many times is not sampled by biopsy, though under the microscope
injury may be seen, though not specific for cause or food. If the
physician is either not suspecting food intolerance or doesn’t routinely
biopsy normal appearing intestinal tissue looking for signs of food
intolerance, the injury may not be discovered.
The immune based food intolerances are commonly associated with many
symptoms that can be both gastrointestinal and outside the gut and may
include bloating, gas, diarrhea (and sometimes constipation), abdominal
pain, nausea, fatigue, headaches, joint and muscle pains, skin rashes,
weight loss or gain, anemia or nutritional deficiencies, irritability,
depression, mental fogginess, and nerve pain (neuropathy). These symptoms
may be misdiagnosed or mislabeled as irritable bowel syndrome, chronic
fatigue syndrome, reflux, ulcer, and fibromyalgia, etc. without another
thought by patient or physician that food intolerance may be the cause and
specific food elimination may be the cure. The common food allergens also
are the most common causes of food intolerance reactions.
Generally, most physicians are aware of common food allergy symptoms
and how and when to test. However, several studies have confirmed most
people’s experience that the majority of primary care physicians are
unaware of the common symptoms of Celiac disease, that blood tests exist
for screening antibodies and the high risk genes, and that it is common
and may be diagnosed in adults. This is why the diagnosis is delayed on
average over 11 years in most adults, after many of them have irreversible
complications such as osteoporosis, cancer, or another autoimmune disease.
The awareness and acceptance of non-Celiac gluten sensitivity and other
food protein intolerances in the medical community is even worse.
Therefore, food intolerance or sensitivity is commonly missed and
untreated. Many patients are forced to self-diagnose by discovery of the
link of their symptoms to specific foods serendipitously, often as a
result of an elimination diet, recommendation of an alternative
practitioner or friend/relative, or search for help on the internet or
multiple physicians for help. Hopefully, by reading this article you now
better understand food allergies and intolerances, why they are often
missed and that they are a common cause of many symptoms, not just
intestinal, that usually improve if not resolve once the offending food or
foods are eliminated from your diet.
 ABOUT
THE AUTHOR
Dr. Scot Lewey is a physician who is specialty trained and board certified
in the field of gastroenterology (diseases of the digestive system) who
practices his specialty in Colorado. He is the physician advisor to the
local Celiac Sprue support group and is a published author and researcher
who is developing a web based educational program for people suffering
from food intolerances,
http://www.thefooddoc.com
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