Cinnamon powder comes from grinding the bark of Cinnamomum trees. Grocery stores usually sell Cassia, while Ceylon is often called true cinnamon. People sprinkle it on food, stir it into drinks, or take it in capsules with meals to help maintain healthy blood sugar.
Cassia contains coumarin, which can damage the liver in large amounts. Ceylon supplies much less coumarin. Cinnamon can interact with diabetes medications and blood thinners. Coumarin adds to the blood-thinning effect. Avoid high doses before surgery.