Gluten is a type of protein found in some but not all grains. Rye, wheat and barley that are found in cereals or many types of bread contain gluten.
The incidence of Americans, especially the elderly, who are intolerant to gluten as doubled every 15 years since 1974, according to findings reported in the September 27, 2010, edition of Annals of Medicine.
Researchers in a 2003 study showed a rate of about 1 in 133 Americans have celiac disease, the autoimmune disorder identified with gluten-intolerance. The rate of occurrence tends to rise as the population ages. A Finnish study suggested that the disease is 2.5 times more common in the elderly than the population in general.
Physicians may want to test for celiac disease when their patients complain of diarrhea, intestinal boating, stomach cramps, joint pain, chronic fatigue or depression. Left untreated the disease interferes with nutrient absorption and small intestine damage.