What are food allergies, intolerances and sensitivities?

What are food allergies, intolerances and sensitivities?

Food allergies are due to IgE antibodies made to certain foods that a person developed for some reason because their body misinterpreted the food as a foreign invading protein. The presence of an IgE antibody to the specific food a person is allergic to results in an immediate immune response from the body to the food when it is eaten. The IgE antibody binds to its specific dietary protein and triggers reactions in the body that include the release of chemicals such as histamine, which can cause symptoms such as itching, swelling, wheezing or difficulty breathing, skin rash or hives, and in severe shock, death if not the other way around. Vomiting and diarrhea may occur but are less common.

Testing for the presence of an allergy to a food or food can be done through blood or skin tests, or both. One of the most common blood tests is the RAST test, which examines the presence of specific IgE antibodies to common food allergens and other foods based on a history that suggests a particular food is suspect. Skin testing is performed by injecting or applying extracts of common and any suspected foods to stung or scratched skin and looking for diagnostic “hive”-like reactions at the site of the suspected food. The most common food allergens are peanuts, cow's milk, wheat, corn, soy, shellfish, eggs, tree nuts, chocolate, pork, tomatoes and citrus fruits.

The terms food intolerance and sensitivity are commonly used interchangeably. They refer to a group of food reactions that are not caused by IgE antibodies. More generally, they refer to any adverse or unpleasant reaction that occurs after consuming a food.

Food reactions that are not caused by allergy can have various 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 intestinal mucous cells. Lactase deficiency can be inherited or acquired. It often occurs when the intestinal lining is damaged. Because the lactase enzymes are located on the outermost surface of the intestine, they are more susceptible to injury. For example, lactose intolerance is common after intestinal flu or untreated celiac disease. Other sugar enzymes may be deficient, or the gut may simply be overwhelmed by too much sugar at once. A classic example is “Big Gulp” syndrome, when someone drinks a huge cola drink and then experiences the “stomach ache” due to the enormous amount of fructose. Large amounts cannot be handled by the intestines, causing bloating, urgency and terrible diarrhea.

A lack of digestive enzymes released in the intestines can lead to poor digestion of food. For example, if the pancreas is chronically damaged (pancreatitis), usually from chronic alcohol abuse, or is congenitally underdeveloped or malfunctioning (e.g., cystic fibrosis). The pancreatic enzyme deficiency that occurs leads to malabsorption, especially of fats, causing symptoms of diarrhea and weight loss. Abnormal bacterial species and levels in the intestine, also called dysbiosis, and abnormal excess levels of "bad" bacteria or the presence of bacteria in the upper small intestine, where little or no bacteria normally occur (bacterial growth), can interfere with digestion, absorption or cause fermentation of foods, leading to symptoms of abdominal pain, bloating, gas and diarrhea.

Some foods and food additives have a direct toxic effect on the gastrointestinal tract. Additives like MSG and sulfites can cause symptoms like hot flashes and diarrhea or “Chinese restaurant” or “salad bar” syndrome.

All foods contain proteins known as lectins. Some of these proteins are very resistant to digestion and toxic to the human intestine, especially if they are not pretreated by soaking, cooking well, or removing toxic parts. For example, inadequately soaked and cooked kidney beans cause food poisoning like illness. There are several foods containing lectins that are poorly tolerated by many people and are deadly to insects and pests. One researcher, Loren Cordain PhD., author of the Paleo diet, has published extensive research on how the human gut is not "evolved" to tolerate many of the foods we eat today but did not eat in the ancient "hunter-gatherer" times, leading to many diseases in modern societies and the increasing epidemic of autoimmune diseases. Some of the “modern” foods that were not part of the ancient diet but make up a large part of our diet now have well-recognized toxic or poorly tolerated proteins called lectins. Examples include wheat germ agglutinin (WGA), casein (cow's milk protein), peanut agglutinin (PNA), soybean agglutinin (SBA), and tomato lectin (TL), which have been shown to be toxic to the human intestine in animal studies. There are few published studies and little active research on the role of dietary lectins in health and disease.

When the reaction is an immunotoxicity reaction to a food protein, intestinal damage often occurs, often referred to as “leaky gut,” due to symptoms of malabsorption or entry of toxic food proteins and/or bacterial products into the bloodstream, resulting in a variety of adverse health effects. This reaction can lead to autoimmunity, where the body attacks itself in the gut or in distant organs or tissues. The response may be supported by abnormal bacterial types and/or levels in the gut (dysbiosis). Symptoms usually develop over time and flare up in just a few hours to three days after eating the offending food and continue if the food is eaten.

Since the protein in the food is usually the cause and such proteins can 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 it to identify the specific food as the cause. For example, gluten (the protein in wheat) and casein (the protein in cow's milk) are found in many foods and are toxic to many people. Over time, people sensitive to such food proteins typically become sicker and may develop enough intestinal injury that blood tests for other types of antibodies, IgG and/or IgA, to the food or certain food proteins are detectable in the blood, stool, or saliva.

A delayed immune response to proteins in the diet (wheat, cow's milk), leading to intestinal injury, gastrointestinal and non-gastrointestinal symptoms, and increased autoimmune disease, is best recognized in celiac disease. It is an autoimmune disease that results from the 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 childhood disease and was rare, especially in the USA. However, blood tests have documented that it occurs in approximately 1 in 133 to 1 in 100 people worldwide, although most sufferers 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 following a gluten-free diet. If left untreated, it is linked to higher rates of cancer, particularly lymphoma, osteoporosis, anemia and other complications of malabsorption, leading to shortened life expectancy. It is treated with a lifelong gluten-free diet. Minor levels of gluten intolerance or sensitivity may not be severe enough to cause abnormal or diagnostic blood tests and intestinal biopsies, but do result in symptoms that improve or resolve with a gluten-free diet and can be detected by elevated stool or saliva antibody tests.

Although intestinal tissue injury may be visually viewed as abnormal appearing tissue during endoscopic procedures, such findings are not specific to the cause. The tissue often appears normal and is therefore often not sampled by biopsy, although lesions may appear under the microscope but are not specific to cause or food. If the doctor either does not suspect a food intolerance or does not routinely examine normal-appearing intestinal tissue for signs of food intolerance, the injury may not be discovered.

Immune-related food intolerances are often associated with many symptoms that can occur both gastrointestinal and extra-intestinal. These include bloating, gas, diarrhea (and sometimes constipation), abdominal pain, nausea, fatigue, headaches, joint and muscle pain, skin rashes, weight loss or gain, anemia or malnutrition, irritability, depression, mental fogginess, and nerve pain (neuropathy). These symptoms can be misdiagnosed or mislabeled as Irritable Bowel Syndrome, Chronic Fatigue Syndrome, Reflux, Ulcer and Fibromyalgia etc. without the patient or doctor once again assuming that food intolerance may be the cause and specific food elimination may be the cure. The most common food allergens are also the most common causes of food intolerance reactions.

In general, most doctors are aware of the most common food allergy symptoms and know how and when to test for them. However, several studies have confirmed the experience of most people, that the majority of primary care physicians are unaware of the common symptoms of celiac disease, that blood tests exist to screen for antibodies and the high-risk genes, and that these are common and can be diagnosed in adults. For this reason, diagnosis is delayed on average by more than 11 years for most adults, after many of them experience 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 often overlooked and untreated. Many patients are forced to self-diagnose themselves by accidentally discovering the connection of their symptoms to certain foods, often as a result of an elimination diet, the recommendation of a naturopath or friend/relative, or seeking help on the Internet or from multiple doctors for help. Hopefully by reading this article you will better understand food allergies and intolerances, why they are often overlooked, and that they are a common cause of many symptoms, not just gut-related, which usually improve if not addressed once the offending food or food is eliminated from your diet.

Inspired by Dr. Scot Lewey