Cassia is what almost all supermarket "cinnamon" is, and it carries coumarin — a hepatotoxin in susceptible people. Ceylon cinnamon (Cinnamomum verum) carries almost none. This is a species distinction, not a quality one, and the label rarely states it.
Also known as: cassia, Cinnamomum cassia, Chinese cinnamon, coumarin, supermarket cinnamon. Category: seasoning.
What it does, mechanism by mechanism
Additive hepatotoxicity — provides, moderate
Two or more agents with documented liver injury signals taken together. Not a pharmacokinetic interaction; the additivity is at the organ.
Woehrlin et al. measured German retail cassia powder at a median of about 3 g coumarin per kg, versus trace amounts in Ceylon cinnamon. EFSA set a coumarin TDI of 0.1 mg/kg body weight per day; a few grams of cassia powder daily can exceed it for an adult. Coumarin hepatotoxicity is idiosyncratic and reversible on withdrawal. NOTE: this coumarin is NOT an anticoagulant — it is not warfarin, and cinnamon is not a blood thinner by this route.
A clean result means NO DOCUMENTED INTERACTION IN THIS DATASET. It does not mean safe, and it is not a clearance. Most substances are not in this dataset at all, and for many pairs that are, nobody has ever studied the combination.
Serotonergic drugs and the serotonin-toxicity mechanism
Dietary tyramine and L-dopa loads
The major cytochrome P450 pathways: CYP3A4, CYP2D6, CYP1A2, CYP2C9, CYP2C19 — inhibition and induction
P-glycoprotein inhibition and induction
11β-HSD2 inhibition (the licorice mechanism) and the potassium consequences that follow it
QT prolongation as an additive pharmacodynamic axis
Culinary seasonings and common foods with documented pharmacological activity
A selected set of narrow-therapeutic-index drugs where those shifts matter most
Not in this dataset
Any substance not named in this dataset — which is most substances. There are tens of thousands of marketed drugs and this table holds fewer than a hundred entries.
Phase-2 conjugation (UGT, SULT, NAT2, COMT) except where a specific entry names it. The oilahuasca corpus turns heavily on phase 2 and this engine models it only in passing.
Pharmacogenomics. CYP2D6 and CYP2C19 are strongly polymorphic; a poor metaboliser and an ultra-rapid metaboliser can have opposite outcomes from the same pair, and this engine does not know your genotype.
Dose, timing, duration, formulation and route — all of which change whether a documented interaction is clinically real for you.
Renal and hepatic impairment, age, pregnancy, and body composition.
Additive sedation, respiratory depression, bleeding risk, hypoglycaemia and most other pharmacodynamic axes beyond the ones listed above.
Herb–herb interactions outside the named entries, and essentially the whole botanical world: most plants have no interaction literature at all.
Allergy, intolerance, and contamination or adulteration of unregulated products.
Anything published after the last-reviewed date below.
72 substances, 20 mechanisms,
64 citations. Last reviewed .
Primary literature (every DOI resolved against the Crossref API) and FDA drug labelling. There is no free, openly-licensed, comprehensive drug-interaction dataset to draw on; NLM retired its Drug Interaction API on 2024-01-02 and DrugBank's interaction set is a commercial licence.
References
Woehrlin F, Fry H, Abraham K, Preiss-Weigert A (2010). Quantification of Flavoring Constituents in Cinnamon: High Variation of Coumarin in Cassia Bark from the German Retail Market and in Authentic Samples from Indonesia. Journal of Agricultural and Food Chemistry. doi:10.1021/jf102112p
Abraham K, Wöhrlin F, Lindtner O, Heinemeyer G, Lampen A (2010). Toxicology and risk assessment of coumarin: Focus on human data. Molecular Nutrition & Food Research. doi:10.1002/mnfr.200900281
EFSA Scientific Panel on Food Additives, Flavourings, Processing Aids and Materials in Contact with Food (AFC) (2004). Opinion of the Scientific Panel on food additives, flavourings, processing aids and materials in contact with food (AFC) on coumarin. EFSA Journal. doi:10.2903/j.efsa.2004.104
Every DOI above was resolved against the Crossref API on 2026-09-09 and the returned
title checked against the one printed here. Three DOIs in the first draft resolved to real but different
papers and were corrected before publication.