Cinnamon (Cassia / Coumarin)

Cinnamon is the spice everyone assumes is harmless, and as a flavouring on your oats or in your coffee, it essentially is. ORIA's caution applies to a specific use: taking cassia cinnamon as a daily, concentrated SUPPLEMENT, usually marketed for blood sugar or weight loss. The pivot point is a compound called coumarin. There are two main commercial cinnamons, and they are not interchangeable: cassia cinnamon (the cheap, common one - Chinese, Indonesian or Saigon) is naturally HIGH in coumarin, while Ceylon or 'true' cinnamon (Cinnamomum verum) contains almost none. Coumarin can cause liver injury: European food-safety authorities set a tolerable daily intake of 0.1 mg per kilogram of body weight - roughly 6 to 7 milligrams a day for an adult - based on liver toxicity in animal studies. Independent laboratory testing found that a single teaspoon of cassia cinnamon contains somewhere between about 8.5 and 15.5 milligrams of coumarin, so even a teaspoon a day of cassia can put you over the limit, and a concentrated cassia capsule taken daily pushes further. On top of the regulatory limit, there are documented - though rare and idiosyncratic - case reports of reversible acute liver injury (jaundice, raised liver enzymes) attributed to cinnamon, resolving once it was stopped. That combination of a clear dose-toxicity mechanism plus real, if uncommon, human cases is why ORIA grades it caution rather than okay - a more concrete liver case than several botanicals it already flags. The good news is that the remedy is trivially simple and worth repeating: if you use cinnamon regularly or in supplement doses, choose CEYLON cinnamon, which is essentially coumarin-free; reserve cassia for occasional culinary use. A quality note: some products labelled 'Ceylon' have tested as cassia, so buy from a reputable source. Finally, a myth to retire - the coumarin in cinnamon is NOT an anticoagulant; it is chemically distinct from the blood-thinning compound warfarin, so the 'cinnamon thins your blood' line is wrong; the genuine concern is the liver. Verdict: love it on your food, but if you're taking cinnamon daily or as a supplement, switch to Ceylon and keep cassia for the spice rack.