In all honesty, I already knew this when I was a small kid in the 1970's :?: It's pretty much common knowledge.

But, seeing as you mentioned it, it's worth making sure you get true cinnamon (Cinnamomum zeylanicum) - the expensive stuff from India - rather than cassia (C. cassia), typically from China and noticeably cheaper. The latter contains quantities of coumarin that can make it hazardous.