People of Irish heritage have a higher possibility of celiac disease, a disorder in the small intestine that causes damage when wheat, barley or rye products are eaten.

Dr. Sheila Crowe, a professor of gastroenterology writing in The New York Times, stated that celiac disease was "most common in the Irish population," and that nowadays it is thought that 1 in 100 are affected by it.  She pointed out that Ireland, like many other European countries, has a very high rate of celiac disease.

Crowe states that that Irish and others "also have the genes that predispose to celiac disease. These genes are in the family of genes for proteins referred to as human leukocyte antigens, or H.L.A. A subset of these genes are involved in autoimmune diseases, and the genes that predispose to celiac disease are in that group.

“Some of these H.L.A. genes can be tested for using a sample of blood or cells taken from your mouth by swabbing the inside of your cheek," she said.