I am reading an excellent book, Healing Spices: How To Use 50 Everyday and Exotic Spices to Boost Health and Heart Disease by Bharat B. Aggarwal, PhD with Deborah Yost. It is an excellent book.
(I would also recommend checking out the book, AntiCancer, 2nd edition by David Servan-Schreiber, MD, PhD. Dr. Schreiber, a medical doctor and a cancer survivor, has written about foods and habits that can help one to survive cancer or to prevent it. See www.anticancerways.com.)
On page 80 of Healing Spices, it mentions that what we commonly call cinnamon in the USA is generally not “true cinnamon,” it’s cassia. “Cassia cinnamon (Cinnamomum cassia) and true cinnamon (Cinnamomum verum) belong to the same botanical family (Cinnamomum.) They also look alike…Cassia is the sweeter and stronger of the two-and the one preferred throughout most of the world (including the US) as a culinary spice. It’s also the version that was used in all the studies discussed in [the chapter on Cinnamon in the book.]“ In some places, such as England, it is not legal to label Cassia as cinnamon. (p.80)
The book includes great recipes using common spices and also discsses spices which you may never have heard of. Check it out!
To Your Health and Cilinary Delight,
-Glenn 
founder,