Lauraceae

Cinnamomum aromaticum

Cassia · Chinese cinnamon · Rou gui · Gui zhi

Mixed Caution

Part used: barkwood
Native range: Southern China and mainland Southeast Asia
Morphology: An evergreen tree to fifteen metres with leathery three-veined leaves. The thick bark is stripped and dries into hard, coarse, dark quills, quite unlike the fine papery scrolls of true cinnamon.
Also known as: Cinnamomum cassia

What is in it

volatile oil cinnamaldehyde

coumarin

procyanidins

Evidence

Trials of cinnamon for glycaemic control in type 2 diabetes are inconsistent; meta-analyses find small effects that do not hold up well and Cochrane finds insufficient evidence. Most trials used cassia rather than true cinnamon.

Safety

The significant issue is coumarin. Cassia contains it at levels high enough that regular consumption of a few grams a day can exceed the tolerable daily intake, and coumarin is hepatotoxic in susceptible people. Danish and German authorities have issued warnings about cassia in baked goods. True cinnamon, Cinnamomum verum, contains far less.

Interactions: Coumarin content raises theoretical concern with anticoagulants; Additive liver risk at high intake

Regulatory: Permitted as a food. Coumarin limits in food apply in the EU and elsewhere.

How the traditions classify it

Galenic Cinnamon was classed as hot and dry in the second or third degree, and was among the most valuable traded drugs of the ancient world.

Chinese Two medicines from one tree. The inner bark, rou gui, is very hot and pungent, used to warm the interior and fortify yang. The young twig, gui zhi, is warm and pungent, used to release the exterior and warm the channels.

Three systems, rating the same plant. Where they disagree, none of them is correcting the others — they are separate frameworks that arrived at their categories independently.

Historical use

Traded from China and Southeast Asia for millennia and recorded in Egyptian, biblical and Greek sources — though ancient references almost certainly cover several species.

Recorded as history and attributed where possible. Long use establishes that a plant was widely used, not that it worked, and not that it was safe.

Worth knowing

Almost all the cinnamon sold in the English-speaking world is not cinnamon. It is cassia, a different species, and the substitution is legal, ancient and unlabelled.

It matters because of coumarin. Cassia carries it at concentrations that make daily supplement- level intake a genuine liver concern, and German and Danish regulators have both acted on cinnamon in baked goods for exactly this reason. Cinnamomum verum contains a small fraction of the amount.

Its accepted name is not the one you will see on a label. Most references, and this entry until it was checked, call it Cinnamomum cassia; GBIF and Kew give priority to C. aromaticum.

You can tell them apart by the stick. True cinnamon rolls into fine, brittle, many-layered scrolls the texture of paper. Cassia is a single thick hard curl. Ground, they are indistinguishable, which is most of the problem.

Nomenclature verified against GBIF backbone taxonomy.