In a meta-analysis…
Cinnamon lowered A1C by 0.09%, versus the usual 1% with medication. [Given that] A1c reflects overall glucose trends, cinnamon doesn’t look that impressive. Even at the extreme of the confidence interval, cinnamon has, at best, 10% of the efficacy of drug treatments. At worst, it’s completely ineffective.
One tasty component of a Cinnabon cinnamon roll
See all the wonky details in a post by pharmacist Scott Gavura at Science-Based Medicine. I would only add that average changes in blood sugar and hemoglobin A1c in clinical studies don’t necessarily apply to an individual; some folks may respond much better than others.
Steve Parker, M.D.
Diabetic Mediterranean Diet 