If you've never heard of celiac disease, you're in good company. Once believed to be a rare condition, experts now estimate that it affects at least one of every 250 Americans.

Celiac disease causes damage to the small intestine and interferes with the absorption of nutrients from food. People who suffer from the disorder cannot tolerate gluten, a natural protein found in grains, including wheat, rye and barley.

When individuals with celiac disease eat gluten-containing foods, their immune systems rebel, launching an attack against tiny intestinal structures called villi. These finger-like projections, which dramatically increase the surface area of the lining of the small intestine, are responsible for absorbing important nutrients from foods in the diet.

Common digestive complaints associated with celiac disease include mild to severe abdominal pain, cramping and bloating, with a perplexing combination of diarrhea, flatulence and constipation. Because the gastrointestinal symptoms are so variable, celiac disease is often difficult to distinguish from other disorders of the gut, including irritable bowel syndrome, ulcerative colitis and intestinal infections.

After repeated assaults from gluten-containing foods, the intestinal villi of affected individuals can become so damaged that they are no longer able to absorb nutrients properly. As a result, people with celiac disease can become dangerously malnourished.

Vitamin K deficiencies can produce bleeding gums or easy bruising, while insufficient vitamin A leads to dry, scaly skin. Poor absorption of vitamin D and calcium can ultimately result in osteoporosis, a debilitating disease that leaves bones brittle and more susceptible to fracture.

Many symptoms of celiac disease may not appear to be even remotely related to the digestive tract, but nutritional deficiencies can affect every system of the body. Celiac disease is known to be a cause of seizure disorders, migraine headaches, and even infertility and miscarriages.

Recent research has demonstrated that celiac disease may be hereditary: Relatives of people affected by the disorder have a greater risk of having it themselves. Individuals suffering from other disorders of the immune system, including type 1 diabetes or thyroid disease, are even more susceptible to developing celiac disease.

Symptoms of celiac disease may arise at any stage of life, from infancy to adulthood. Babies and children with the disorder may suffer from abdominal pain, diarrhea and developmental delays. Affected teenagers may experience delayed puberty and remain short in stature.

In some youngsters, the condition is so mild that it goes unrecognized and undiagnosed until adulthood. Emotional stress, surgery, pregnancy or an illness may trigger the first overt symptoms in people with the disease.

Once the condition is suspected, doctors can perform specific tests that lead to the correct diagnosis. Although new blood tests for celiac disease have been developed in recent years, biopsy and microscopic examination of intestinal tissue are thought to provide the most accurate diagnosis.

At this point, there is no known cure for the disease. The current treatment of choice is to follow a gluten-free diet, avoiding all food products that contain wheat, rye and barley.

Whether patients should avoid oats is less certain. Some individuals with celiac disease can tolerate them, while others cannot.

Maintaining a gluten-free diet sounds simple enough, but it's easier said than done. Many of the foods that Americans regularly eat and enjoy are rich in gluten, including most pastas, breads and cereals.

Although it may not show up on a package's list of ingredients, gluten can be found in a wide variety of seemingly innocent foods, including canned soup, ice cream and processed meats. Hidden sources of the troublesome protein include many additives, preservatives and stabilizers found in products ranging from mouthwash to prescription medications.

As if gluten intolerance isn't bad enough, some people with untreated celiac disease can't tolerate lactose, the milk sugar found in dairy products.

Fortunately, lactose intolerance is often a temporary condition caused by wheat-related damage to the intestinal lining. Following a gluten-free diet promotes intestinal healing, and in many cases, a restored ability to properly digest dairy products.

Plain meat, fish, rice, fruits and vegetables are free of both gluten and lactose, and can be safely consumed by people with celiac disease. Many supermarkets and health food stores offer gluten-free breads, pastas, cereals and snack foods made of rice, soy and bean flour.

Unless it's suspected, celiac disease is a condition that is difficult to recognize, diagnose and treat. The good news is that with careful attention to diet and lifestyle, individuals with this potentially devastating disorder can remain healthy and symptom-free for life.

Rallie McAllister is a board-certified family physician, speaker and the author of several books, including "Healthy Lunchbox: The Working Mom's Guide to Keeping You and Your Kids Trim." Her website is www.rallieonhealth.com. To find out more about Rallie McAllister, M.D., and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate Web page at www.creators.com.

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