US Pharm. 2013;38(12):HS-9-HS-13.

In recent decades, the prevalence of food allergy has appeared to be on the increase. Even a tiny amount of an allergy-causing food can trigger signs and symptoms such as digestive problems, hives, or swollen face and airways (angioedema). Wheat allergy is one of the most common food allergies in children and may occur in the absence of a family history. Wheat allergy may sometimes be diagnosed as celiac disease (an autoimmune disease), but the two conditions are different. Wheat allergy generates an allergy-causing antibody to proteins found in wheat. Celiac disease, on the other hand, is an abnormal immune-system response in the small intestines to the gluten in wheat (mainly the gliadin part) and is probably always inherited.1

Gluten is the insoluble protein constituent of wheat and other grains (rye, oats, and barley) and is obtained from flour by washing out the soluble starch. In some people, ingesting gluten results in potentially life-threatening malabsorption. Although avoiding wheat is the primary treatment for wheat allergy, medications may be necessary to manage allergic reactions to wheat in certain situations.1

A gluten-free diet is a diet in which wheat and other grains such as barley, oats, and rye are avoided. Exceptions to this essentially grain-free diet are corn, rice, millet, and wheat starch that has been washed free of gliadin.

A gluten-free diet can relieve the problems associated with gluten allergy. However, enjoying gluten-free meals demands some motivation. Patients, as well as family members who purchase and prepare patients’ foods, should read the labels on processed foods very carefully. Many  such foods contain hidden and unexpected wheat flour. If there are any questions about the contents of a product, manufacturers will provide lists of their foods that are permissible on a gluten-free diet.2

Gluten

There are two groups of proteins that constitute gluten: the gliadins and the glutenins. Gliadins are monomeric proteins that can be separated into four groups, alpha-, beta-, gamma-, and omega-gliadins, which give dough its flow characteristics. Glutenins occur as multimeric aggregates of high-molecular-weight and low-molecular-weight subunits held together by disulfide bonds. Glutenins are proteins of wheat that give elasticity in finished wheat products.2

Gliadin is the protein in wheat and other cereals that is responsible for triggering the symptoms of celiac disease. People with celiac disease have a genetic predisposition to be sensitive to this protein, and their bodies make gliadin antibodies that can be detected in a test for the presence of the disorder. There are different kinds of gliadins, and the body makes different antibodies depending on the type of protein present. These are referred to as antigliadin antibodies (AGAs).2

Gliadin Antibody Tests

A gliadin antibodies test is used as part of an evaluation for celiac disease. The gliadin portion of the protein found in gluten is mistakenly recognized as a foreign invader by the immune system. The immune system of someone who is sensitive to gliadin produces AGAs to attack the protein. These antibodies are divided into two groups: immunoglobulin A (IgA) and immunoglobulin G (IgG).3

The IgA antibody is more useful in detecting celiac disease because it is made in the small intestine, where gluten causes inflammation and irritation in sensitive people. The IgG antibody levels, on the other hand, are less specific to celiac disease but may still be useful in diagnosing autoimmune problems, especially in people who are deficient in IgA. Wheat allergy, which is caused by the presence of IgE antibodies, is not mediated by either of these antibodies.3

Two other blood tests are the antireticulin antibody (ARA), in which IgG antibodies are examined through an immune-fluorescent microscope, and the antiendomysium antibody (AEA) assay, which identifies IgA antibodies against the endomysial tissue.

The levels of both types of gliadin antibodies in the blood can assess the immune system’s response to gluten. The blood sample usually will undergo a test called an ELISA (enzyme-linked immunosorbent assay). This method involves incubating the blood on a specialized plate with various chemicals. By measuring the intensity of the color change that follows, physicians can tell whether gliadin antibodies are present in the blood. The results are commonly available within 1 to 2 days. It has been reported that as little as 0.1 g of ingested gluten can trigger symptoms.

If results show the presence of gliadin antibodies, further tests will be performed, which may include a biopsy of the small intestine to look for evidence of gliadin-induced inflammation. A small-intestinal mucosal biopsy remains the cornerstone for diagnosis.3

Epidemiology

About 3 million Americans (at least 1 in 150 people) have been diagnosed with celiac disease. In countries such as Sweden, the incidence is as high as 1 in 133 people. Growing awareness of the condition, combined with consumer demand, has brought an increasing number of gluten-free products to store shelves in recent years. (While people with celiac disease have little choice but to avoid gluten, other people may avoid gluten in an effort to lose weight. That may work—but it may not be the best way to trim pounds.4)

Gluten Intolerance

Many people have gluten intolerance, as opposed to a true gluten allergy, but the symptoms can be just as debilitating. Gluten intolerance can produce symptoms such as gas, abdominal pain, bloating, and diarrhea, which commonly occur after eating the wheat, rye, or barley found in most grain-based products. Gluten intolerance often causes symptoms similar to those of celiac disease; however, with intolerance to gluten no damage occurs to the small intestine. Many symptoms of gluten intolerance are resolved by consuming a gluten-free diet. Gluten-free diets eliminate grain products such as pasta and bread. Dietary counseling with a registered dietitian who specializes in gastrointestinal conditions is beneficial for those with gluten intolerance. Those who continue to have adverse effects from wheat should be tested for celiac disease or other autoimmune disorders. It is estimated that there are more than 20 million people with a nonceliac gluten sensitivity or wheat allergy in the United States.5

Celiac Disease

A primary cause of gluten allergies in many people is celiac disease, defined as a hereditary condition in which the person is allergic to gluten. Damage to the small intestine can occur, along with diarrhea, fatigue, weight loss, and overall poor health. A biopsy of the small intestine can also provide a diagnosis of celiac disease. Damage to the small intestine is discernible because those who suffer from celiac disease do not have an adequate number of villi in the lamina propria and crypt regions of their intestines. This deficit is caused by the reaction to specific food-grain antigens (toxic amino acid sequences) found in wheat, rye, and barley. People who have celiac disease often develop an itchy rash known as dermatitis herpetiformis. Having celiac disease also increases the risk of developing cancer of the digestive tract, osteoporosis, anemia, and thyroid disorders.6

Other conditions may also involve a gluten reaction, at least in some individuals. Diseases in the autoimmune class, such as fibromyalgia, type 1 diabetes, Crohn disease, ulcerative colitis, and rheumatoid arthritis, have also shown improvement when gluten is removed from the diet. As a result, many with these conditions now follow a gluten-free diet, including persons who have irritable bowel syndrome. People with polymyalgia rheumatica and rheumatoid arthritis have been able to taper their steroid regimen by following a gluten-free diet.

According to research reports, a significant number of patients with autoimmune thyroid disease (Hashimoto disease and Grave disease) also have celiac disease. Other researchers have found that thyroid autoantibodies will disappear after 3 to 6 months of a gluten-free diet.6

Where Gluten Hides

Gluten is the common name for the proteins found in specific grains, and it is found in all forms of wheat. Examples of gluten-containing foods include breads, cookies, crackers, cake mixes, cereal, ice cream, packaged meats and cold cuts, pasta, and even soup broths. Anyone with celiac disease must be cautious about purchasing products that were manufactured in facilities that also process gluten products. These items are often labeled as “contains wheat ingredients” or “made on shared equipment that also processes wheat.”6

Oats do not naturally contain gluten, but they are often grown near fields of wheat and rye. Since farmers may rotate their fields, people who need to avoid gluten should eat oats only if they are from certified gluten-free sources. The ultimate relief from wheat allergy symptoms comes from following a gluten-free diet.

REFERENCES

1. Food Allergy and Anaphylaxis Network. Wheat allergy facts, symptoms. December 17, 2009. www.foodallergy.org/page/wheat-allergy. Accessed January 6, 2010.
2. Hadjivassiliou M, Sanders DS, Woodroofe N, et al. Gluten ataxia. Cerebellum. 2008;7:494-498.
3. van Eckert R, Bond J, Rawson P, et al. Reactivity of gluten detecting monoclonal antibodies to a gliadin reference material. J Cereal Sci. 2010;51(2):
198-204
4. Rewers M. Epidemiology of celiac disease: what are the prevalence, incidence, and progression of celiac disease? Gastroenterology. 2005;128(4 suppl 1):S47-S51.
5. Wheat allergy. www.mayoclinic.com/print/wheat. Accessed November 6, 2012.
6. Helms S. Celiac disease and gluten-associated diseases. Alt. Med. Rev. 2005;10(3):172-192. www.thorne.com/media/Celiac.pdf. Accessed November 15, 2012.

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