1- Might result in liver damage
Coumarin is abundant in cassia (or ordinary) cinnamon.
While Ceylon cinnamon only has negligible levels of coumarin, pulverized Cassia cinnamon contains a range of 7 to 18 milligrams of coumarin per teaspoon (2.6 grams).
A 130-pound (59-kg) individual can consume 5 mg of coumarin daily, or roughly 0.05 mg per pound (0.1 mg per kilogram) of body weight. Accordingly, consuming even a single teaspoon of cassia cinnamon might cause you to exceed the daily limit.
Sadly, a number of studies have revealed that consuming too much coumarin may result in liver toxicity and damage.
For instance, a 73-year-old lady who had been taking cinnamon pills for just one week suddenly had a liver infection that damaged her liver. But in this instance, the dosage was larger because of the supplements used than it would be from food alone.