Thursday, December 18, 2008

What Is Celiac Disease?

Celiac disease, also known as sprue, is a digestive disease that damages the small intestine and interferes with the absorption of nutrients from food. Portions of the small intestine damaged by celiac disease resemble skin damaged by oozing eczema. The intestine becomes porous to relatively large particles of partially digested food, and a generalized allergy-like reaction throughout the entire body can result.

On the other hand, celiac disease is not itself an allergy like asthma, hay fever, or hives. It differs from these kinds of immune processes in that the inflammation underlying celiac disease is localized in the intestine, and is not due to a systemic immune imbalance. Celiac disease also differs from allergy in that it causes a thickening of the tissues it attacks. The muscles surrounding the intestine release collagen to form a scaffold to hold the damaged intestine in place.

The destructive reaction in celiac disease is an attack on just one specialized protein, the enzyme that releases glutamine from wheat and similar grains. An immune globulin called IgA accumulates in the small pockets or villi lining the small intestine and treats them as if they had become infected.

The villi are especially important for absorbing essential fatty acids and fat-soluble vitamins. When they are attacked by the immune system, fat and the fat-soluble vitamins D and K fail to be absorbed and remain in the stool. This results in bulky, foul-smelling, frothy, greasy stools and diarrhea as well as serious nutritional deficiencies of vitamins and essential fatty acids.

Clinical signs celiac disease are remarkably varied. There may be deficiencies of some nutrients but not others, vague gastrointestinal complaints such as bloating, abdominal pain, diarrhea, constipation, flatulence, and dyspepsia and non-gastrointestinal complaints such as fatigue, depression, joint pain, milk intolerance, osteomalacia or osteoporosis, and iron deficiency anemia.

Scientists do not know what triggers celiac disease, but the first symptoms of the condition may not occur until the sufferer has been exposed to a particular colds virus, adenovirus 12. It has also been observed, but not explained, that breastfeeding seems to prevent the development of celiac disease later in life. Occasionally, people who go on diets based exclusively on whole grains develop the disease.

Celiac disease does not cause symptoms unless the lining of the intestine comes in contact with gluten. Bakers think of gluten as the sticky part of any grain, including corn and rice, grains that are safe for celiac patients to consume. Nutritionists use the terms gliadin and glutenin to refer to the storage proteins of wheat and use other terms for the proteins of barley (prolamin), rye (hordein), and oats (avidin). As the nutritionist Joseph Murray points out, it is more useful to inquire whether a food has any ingredient that is in any way derived from or processed with wheat, barley, rye, or oats than to ask, ”Is this food gluten free?”

As in canker sores, much of the damage caused in celiac disease is a result of cell-mediated immunity. The Th1 cells of the bloodstream that engulf and digest infectious microorganisms are activated to engulf and digest healthy cells of the lining of the intestine. Because Th1 cells are triggered by relatively large particles of undigested food, it is helpful for people with celiac disease to chew food thoroughly, and to avoid broths, stocks, and gelatins.

The key to controlling celiac disease, however, is a gluten-free diet. Most medical authorities note that about 10 percent of people with the disease do not respond even to rigorous elimination of gluten products from the diet. Eliminating milk and eggs can help most of people in this group. If you absolutely avoid gluten, however, you will eventually be able to tolerate most other foods.

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