原因如下：

There are three important differences between Ceylon cinnamon and the cassia group of cinnamon species that we would like to point out. First, as a medicinal herb, Ceylon cinnamon is better researched, especially in its extract form, than the cassia cinnamons. Researchers know more about the anti-bacterial properties of Ceylon cinnamon extracts, for example. Second, Ceylon cinnamon has been shown to contain far lower amounts of a naturally occurring substance called coumarin, which can pose toxicity risks if consumed in an excessive amount. Some studies have found one teaspoon of cassia-type cinnamon to contain between 5-12 milligrams of coumarin. Outside of the U.S., organizations like the European Food Safety Authority have recommended no more than 0.1 milligrams of daily coumarin intake from food per 2.2 pounds of body weight. For a person weighing 150 pounds, this recommendation translates into about 7 milligrams of coumarin. These numbers show how it would be possible for a person routinely consuming sizeable amounts of cassia-type cinnamon to increase his or her risk of potential toxicity problems. By contract, Ceylon cinnamon has been shown to contain only trace amounts of coumarin, greatly lowering or actually removing this coumarin-related risk. Third, individuals who report the experience of adverse reactions to cassia-type cinnamon sometimes also report the ability to tolerate Ceylon cinnamon. It is not clear, however, what role coumarin-content might or might not play in this adverse reaction context.