Celiac disease affects about one in 100 people in the U.S. It is a genetic condition, occurring in those who can't tolerate gluten, which is present in grains such as wheat, rye, barley and couscous.

When a person who has celiac disease eats foods that contain gluten, he or she has a toxic reaction that damages the small intestine, preventing food from being properly absorbed into the body.

Celiac disease most commonly strikes people in their 50s with a host of unpleasant symptoms. Half have diarrhea. Other gastrointestinal symptoms include abdominal bloating, vomiting, constipation and stomach pain.

Symptoms of celiac disease can go beyond the abdomen and include fatigue, numbness in hands and feet, weight loss, joint pain, seizures, anemia and an itchy skin rash. Those who have celiac disease are at increased risk for developing osteoporosis. And those who have diabetes mellitus and hypothyroidism are at increased risk of developing celiac disease.

Because many symptoms involve digestive issues, celiac disease is often misdiagnosed, particularly as irritable bowel syndrome. Microscopic colitis also can cause similar symptoms.

Those with chronic abdominal symptoms should be checked by measuring blood levels of autoantibodies, such as tissue transglutaminase or antiendomysial antibodies. In addition, if you have symptoms and relatives who have celiac disease, you should get special genetics tests. A biopsy of your small intestine can confirm the diagnosis and determine the amount of damage present.

However, even if diagnostic tests show you don't have celiac disease, sometimes switching to a gluten free diet, which is the treatment for celiac disease, improves abdominal symptoms.

Following a strictly gluten free diet can be tricky, though. Gluten can be in many foods, some you would not suspect. Gluten is present in bread, pasta and breakfast cereals. Other products, such as processed sausage, soup, ice cream, lipstick and some medicines, can contain gluten.

Eating foods that have even a speck of gluten can cause health problems for those who have celiac disease, so it's important to look for the crossed wheat sign on labels, which indicates foods are gluten free.

SLUCare physician John Morley is director of geriatrics at St. Louis University and a geriatrician at St. Louis University Hospital and Des Peres Hospital. Email him at morley@slu.edu. The Aging Successfully column for older people rotates each week with XX Files, a women's health column.