(Caveat: Long term studies are needed to confirm this as useful treatment for long-term use.)
So it turns out (questionable website, but check the source) that cinnamon and magnesium together can help dramatically lower blood pressure; more even than any medication can. Crazy stuff.
Cinnamon by itself also appears to essentially act like insulin, controlling blood sugar levels - a huge boon for diabetics.
Oh, and it helps reduce your LDL (bad) cholesterol.
Edit: However, it appears that this is only true for Cassia cinnamon, the cheap kind from China as opposed to Ceylon cinnamon which some people call “true cinnamon”. The problem is that cassia has a high amount of coumarin, which thins the blood and is bad for your liver.
As a flavoring for my DIY soylent, I’m personally finding that 2g of cinnamon/day makes my soylent go from acceptable to tasty.
Edit2: Switched to Ceylon cinnamon to avoid coumarin, and it’s both more expensive per gram and not as strong. I use 4g of it, and even with that it still doesn’t give the kick that cassia did.