Cinnamon has the potential to cause several dangerous medical side effects because of the coumarin it contains. Amounts normally used could cause serious health issues.
Commonly used amounts of cinnamon may cause adverse health effects due to its content of coumarin, according to a new study in Norway published in the journal Food and Chemical Toxicology. Coumarin is toxic to the liver, is an anticoagulant (it thins the blood), and causes cancer in rodents. The Norwegian researchers established a new Tolerable Daily Intake (TDI) for coumarin of 0.07 mg per kg of bodyweight per day. By using cinnamon on oatmeal or other cereals just a few times a week, it’s estimated that the TDI in children and adults can be greatly exceeded. Researches stated that even a few weeks of ingesting high amounts of coumarin can be dangerous to our health.
Another group of researchers had previously proven that the absorption of coumarin from Cassia cinnamon is almost the same as that absorbed from isolated (pure) coumarin. Thus, we can rely on the TDI for coumarin to measure the risk of coumarin ingestion from cinnamon. This study was performed on humans, and was published in the journal Molecular Nutrition & Food Research.
The type of cinnamon used might be part of the problem. There are two main types of cinnamon, Cassia and Ceylon. The Cassia cinnamon powder has much more coumarin than the Ceylon type. It’s hard to detect which type is Ceylon if you buy the powder form, although Ceylon has a more subtle flavour. But if you buy cinnamon sticks, the Ceylon bark will have many thin layers.
Cassia cinnamon should only be used sparingly, as a very light sprinkling, and not in teaspoon amounts. The safer option is to use the Ceylon type.