
Ikhlas Khan and colleagues explain that cinnamon, which comes from the bark of certain trees, is one of the most important flavoring agents used in foods and beverages. "True," or Ceylon, cinnamon is expensive, so most breads, sticky buns and other products in the United States use dried cassia bark, or cassia cinnamon.
Ceylon cinnamon contains very little coumarin, a naturally occurring substance that has been linked to liver damage in people sensitive to the substance. However, cassia cinnamon can contain larger amounts. Khan's team decided to check on the coumarin content of a wide variety of food products.
"As found in this study, coumarin was present, sometimes in substantial amounts, in cinnamon-based food supplements and cinnamon-flavored foods," they say.