Scientists are reporting that a 'huge' variation exists in the amounts of coumarin in bark samples of cassia cinnamon from trees growing in Indonesia.
That natural ingredient in the spice may carry a theoretical risk of causing liver damage in a small number of sensitive people who consume large amounts of cinnamon, say Friederike Woehrlin and colleagues.
There are two main types of cinnamon: Ceylon cinnamon (also known as "true" cinnamon) and cassia cinnamon.
Ceylon grows in Sri Lanka, the Seychelles, and Madagascar; however, Cassia generally comes from China and Indonesia.
The scientists analysed 91 cinnamon samples purchased from stores in Germany.
They found that coumarin levels varied widely among different bark samples of Cassia cinnamon.
Therefore they analysed cassia bark samples of five trees received directly from Indonesia and found a huge variation even among samples collected from a single tree.
The study confirmed that cassia cinnamon has the highest levels of coumarin, while Ceylon had the lowest levels.
On average, cassia cinnamon powder contained up to 63 times more coumarin than Ceylon cinnamon powder and cassia cinnamon sticks contained 18 times more coumarin than Ceylon sticks.
"Further research is necessary to identify factors influencing the coumarin levels in cassia cinnamon and to possibly allow the harvesting of cassia cinnamon with low coumarin levels in the future," noted the report.
The report appeared in ACS' bi-weekly Journal of Agricultural and Food Chemistry.