Ceylon cinnamon
The cinnamon you can use daily, because the compound that burdens your liver is not in it.
How to use it
Through oats, yoghurt, coffee, baking, and through savoury stews. Daily is fine, and that is exactly why this is the species.
The best version
True Ceylon, Cinnamomum zeylanicum, recognisable as a quill made of many thin layers, like a cigar. Cassia is one thick, hard bark that curls over. If the jar just says cinnamon, it is almost always cassia.
How to prepare it
Simmer a quill and take it out again, or use it ground over food. Ground cinnamon loses its smell quickly, so buy small jars.
What it does
The advantage of Ceylon is what is missing from it. Coumarin can damage the liver and is present in cassia, the cheap cinnamon in nearly every jar. Ceylon cinnamon does not contain it, which is why the European risk assessors proposed replacing cassia with it.
Watch out
The story about cinnamon and your blood sugar is about the other species. In this trial, people with impaired glucose tolerance took 6 grams of Ceylon cinnamon with a glucose load, and nothing happened to their glucose or their insulin. The drops you read about everywhere come from cassia, which is the cinnamon with the coumarin in it.