What is Celiac Disease?
Pasta, breads, pastries and many other foods enjoyed in the Western diet contain a protein, gluten, which elicits an insidious immunologic reaction in our small intestine capable of far reaching consequences.
Celiac disease results when gluten, a protein found in wheat, rye and barley, interacts with immune cells in our small intestine. The activated immune cells lead to atrophy of the small intestinal lining. The loss of lining surface area as well changes in permeability of the lining result in loss of the ability to digest and absorb many dietary nutrients. Nutrients which may be poorly absorbed include carbohydrates, proteins, fats, iron, calcium and vitamins. Therefore, celiacs may display symptoms such as weight loss, growth failure, diarrhea, fatigue (from iron deficiency anemia) or bone fractures (from osteoporosis).
Celiac disease is one the easiest conditions to diagnose. Most celiacs on a gluten containing diet have circulating antibodies which are readily detected. In the past, blood tests for gliadin antibodies were used, but more sensitive and specific antibodies to TTG (tissue transglutaminase) and endomysium are used today. If it is necessary to confirm the degree of intestinal injury, a painless endoscopic biopsy is performed by a gastroenterologist. On a gluten free diet, the quantity of antibodies will decrease and the biopsy appearance of the intestine improves.
The only thing most celiacs need do is change their diet. The difficult part is that all foods containing wheat, barley and rye must be avoided, usually completely. Can you imagine a college student surviving without pizza, spaghetti, or bread? Even compliant patients may have their diet sabotaged by foods cross contaminated by gluten during food processing or by inadequate labeling of foods. In Europe and America foods labeled “gluten free” may contain 100 ppm and 20 ppm of gluten respectively. Many celiacs do consume some gluten. While they may not have symptoms, many suffer ongoing damage to the small intestine which in some cases is detectable only by biopsy of the intestine.
Celiac disease not only requires the ingestion of gluten in the diet but also a genetic predisposition. Specific predisposing genotypes (HLA-DQ2 and HLA-DQ8) are necessary for a person to be at risk. These genes are found in about 30% of Caucasians in Europe and North America and about 10% of the population of India. Additional genes are also necessary for the disease to fully develop. As a result only about 1% of the populations of Europe and North America have celiac disease. Celiac disease is more common in individuals with type I diabetes, thyroiditis, and some other autoimmune or genetic conditions.
Carbohydrates (starches, sugars, fiber) found in grains, fruits and vegetables, when incompletely digested and absorbed by our digestive tract, reach the colon where bacteria ferment carbohydrates and generate various gases. Individuals with irritable bowel syndrome are particularly likely to suffer from excessive gas bloat due to bacterial carbohydrate fermentation. However, only 3% of irritable bowel patients have celiac disease. The conclusion that gas bloat after ingestion of grain based foods is the result of celiac disease is usually incorrect and is the reason celiac disease is sometimes “over diagnosed”. Some people may also have an allergy to wheat and other plant proteins. This is different from celiac disease and is not specific to gluten.
Detoxifying wheat by pretreatment with bacterial derived peptidases to predigest the toxic proteins found in gluten has been studied. Genetically modified wheat, devoid of the biologically active proteins, is another alternative under study. Altering the immune responsiveness or barrier function of the small intestine is also under study. Diet will remain the mainstay of treatment for the foreseeable future.
Check out these resources online for further reading:
National Foundation for Celiac Awareness: www.celiaccentral.org/
American Celiac Society: www.americanceliacsociety.org
Celiac Disease Foundation: www.celiac.org
National Celiac Association (NCA): www.nationalceliac.org
Gluten Intolerance Group of North America: www.gluten.org
National Center for Nutrition and Dietetics: www.eatright.org