Coumarins
What slows things down
The cut-hay aroma of cinnamon — and the only molecule in the catalog where the variety changes everything.
Effects
The cut-hay scent of Chinese cinnamon hides a molecule that, at high repeated doses, can damage the liver of sensitive people. A child reaches the tolerable daily intake much faster than an adult.
Coumarin gives its scent to freshly cut hay, tonka bean and sweet woodruff. EFSA set its tolerable daily intake at 0.1 mg per kilo of body weight, based on the liver damage seen in sensitive people (EFSA, 2008).
Chinese cinnamon often contains 2 to 5 g per kilo: a teaspoon, about 2.5 g, can thus provide 5 to 12 mg, when a 60 kg adult is allowed 6 mg and a 15 kg child 1.5 mg (BfR, 2012).
By age: children exceed it fastest, because of their low weight; Christmas cinnamon cookies have been the subject of warnings in Germany for this reason.
Sources: EFSA, 2008 · BfR, 2012
The remedy
Chinese cinnamon (cassia), the supermarket kind, contains enough that a few grams a day exceed an adult's tolerable daily intake. Ceylon cinnamon is almost free of it: for daily use, that is the one to buy. The catalog distinguishes the two: logging “Ceylon cinnamon” therefore raises nothing here.