Ceylon Cinnamon vs Cassia: Active Compounds, Clinical Evidence, and Coumarin Safety

Cinnamomum verum — Species Identity, Safety Profile, and the Evidence Base for Repeated-Use Applications

Nalin Siriwardhana, PhD, FACN   ·   Nutritional Scientist

Ceylon Nutritionals · Science & Education Series · March 2025

01 · Definition & Historical Context

Cinnamomum verum— commonly known as Ceylon cinnamon or true cinnamon — is the inner bark of an evergreen tree native to Sri Lanka, belonging to the Lauraceae family. It is one of four commercially significantCinnamomumspecies, alongsideC. cassia(Chinese cinnamon),C. loureiroi(Vietnamese/Saigon cinnamon), andC. burmannii(Indonesian/Korintje cinnamon). The namesCinnamomum verumandCinnamomum zeylanicumrefer to the same species; both appear in the scientific literature, withC. verumbeing the currently accepted botanical nomenclature.

Species identity matters for two reasons directly relevant to supplementation: the four commercial species differ substantially in phytochemical composition and bioactive compound profiles, and they differ by orders of magnitude in coumarin content — a naturally occurring compound with established hepatotoxic potential at elevated intakes. Understanding which species is present in any cinnamon ingredient is therefore a prerequisite for interpreting the scientific literature or making sourcing decisions.

Historical records document cinnamon in Egyptian ritual and embalming contexts by approximately 2000 BCE.1 The ancient Ayurvedic medical tradition, whose earliest texts are associated with compilations spanning several centuries BCE, includes cinnamon bark among documented medicinal preparations. Classical Greek physicians Dioscorides (~40–90 CE) and Galen (~130–210 CE) recorded its properties. Ibn Sina (Avicenna, ~980–1037 CE) catalogued cinnamon in hisCanon of Medicine. Pliny the Elder recorded in the first century AD that cinnamon was priced at approximately fifteen times its weight in silver.1

This convergence of independent recognition across unrelated civilisations spanning more than two millennia does not constitute proof of modern pharmacological efficacy. It establishes cultural significance and provides a well-documented rationale for scientific investigation — which has proceeded actively over the past three decades.

02 · Phytochemistry

The bark ofCinnamomum verumcontains a phytochemically complex mixture. The dominant constituent is trans-cinnamaldehyde — principally responsible for cinnamon's characteristic aroma — which inC. verumbark essential oil typically comprises approximately 50–70% of the volatile fraction, with higher values reported in some studies depending on geographic origin and analytical method.2

C. verumbark is associated with a class of polyphenols called Type-A proanthocyanidins (PAC-A), which have been studied for potential interactions with insulin signalling pathways and represent a key standardisation target in several recent authenticatedC. verumclinical studies. It is important to note that eugenol — a phenolic with antioxidant properties — is present at significant concentrations inC. verumleafoil (typically 70–90%), but at much lower concentrations in thebarkoil used in supplementation (typically below 5% in most analyses).2 This distinction matters when evaluating claims about eugenol in cinnamon bark products.

Mechanistic research — conducted primarily in cell culture and animal models — has described several plausible molecular interactions. Cinnamaldehyde and PAC-A polyphenols have been shown in preclinical models to inhibit alpha-glucosidase and alpha-amylase (digestive enzymes involved in starch breakdown), upregulate GLUT4 glucose transporter expression in skeletal muscle cells, activate the PI3K/Akt insulin-signalling cascade, and modulate NF-κB-mediated inflammatory pathways.32 These are mechanistic findings from laboratory conditions — they establish biological plausibility and guide clinical hypothesis formation, but do not establish clinical outcomes in humans.

03 · Clinical Evidence Review

The U.S. National Center for Complementary and Integrative Health (NCCIH), part of the National Institutes of Health, provides essential framing for the cinnamon literature: many cinnamon studies are difficult to compare because the species or plant part used may not be clearly specified, and current evidence does not clearly support the use of cinnamon for any specific health condition.4 This underscores why species authentication is essential for interpreting any specific study.

What does research say about cinnamon and blood sugar?

Blood glucose and metabolic health: where is the evidence strongest?

A 2025 systematic review inNaunyn-Schmiedeberg's Archives of Pharmacology(Beheshti et al.) synthesised available in vitro, in vivo, and some clinical data onC. zeylanicum's metabolic properties, identifying a consistent pattern of reported anti-diabetic, anti-dyslipidaemic, and anti-inflammatory activity across study designs — while noting that the majority of reviewed studies are preclinical, and that further large-scale human trials are needed.3

Cognitive function: is the evidence sufficient to draw conclusions?

Antimicrobial properties: what does in vitro research show?

04 · Species Comparison & Safety

The four commercially significantCinnamomumspecies differ substantially in phytochemical composition and, most consequentially from a safety standpoint, in coumarin content. Coumarin is a naturally occurring compound with known hepatotoxic potential at elevated intake levels, and its concentration varies by several orders of magnitude across species.

The European Food Safety Authority (EFSA) has established a Tolerable Daily Intake (TDI) for coumarin of 0.1 mg per kilogram of body weight per day.10 For a 70 kg adult, this corresponds to approximately 7 mg per day. A single teaspoon of ground cassia (~2.6 g) may contain 7–20 mg of coumarin — placing daily cassia use at or near the EFSA TDI. The German Federal Institute for Risk Assessment (BfR) has specifically flagged children as a population of concern, given that their lower body weight results in proportionally higher coumarin exposure per gram consumed.11

In a 60-sample retail analysis in Czech markets (Blahová & Svobodová, 2012), cassia samples ranged from 700 to over 7,000 mg/kg coumarin, while the Sri LankanC. verumsample registered below the analytical detection limit.9 A 2018 review inClinical Pharmacology & Therapeutics(Oketch-Rabah, Marles, and Brinckmann) demonstrated that species mislabelling in commerce makes it difficult to apply clinical findings to specific ingredients without confirmed species identity.12

COUMARIN CONTENT BY SPECIES — ANALYTICAL DATA & SAFETY ASSESSMENT

Sources: Blahová & Svobodová (2012), The Scientific World Journal (PMC3385612; PubMed 22593682) · EFSA Scientific Opinion on Coumarin (2004; doi:10.2903/j.efsa.2004.104) · BfR Health Assessment No. 043/2006. Coumarin content varies by origin and analytical method; ranges represent published analytical data.

EVIDENCE SYNTHESIS

Four Evidence-Based Conclusions About Ceylon Cinnamon

1. Historical significance is real, but distinct from clinical proof. The independent recognition of cinnamon across ancient Egyptian, Ayurvedic, Greek, Roman, and Arab medical traditions is a genuine historical phenomenon that frames the modern scientific investigation. It does not constitute evidence of pharmacological efficacy for any specific health outcome.

2. Human clinical evidence is most developed for blood glucose endpoints — with important caveats. The most methodologically rigorous species-authenticated trial to date (Muthukuda et al., 2025) found a statistically significant fasting blood glucose effect as a secondary outcome; the primary endpoint (LDL-C reduction) was not met. Current evidence does not support using cinnamon to manage or treat any clinical condition. Larger confirmatory trials are needed. These findings should be interpreted within the context of study size, duration, and endpoint hierarchy.

3. Species identity is the most important variable in interpreting cinnamon research. The coumarin differential between C. verum and cassia spans two to three orders of magnitude. Conclusions from cassia-based research cannot be applied to C. verum. Any cinnamon supplement should be species-authenticated, with coumarin content documented.

4. Cinnamomum verum is one of the most clearly characterised commercial cinnamon species for repeated-use supplementation contexts. It presents the lowest documented coumarin burden, the most rigorous species-authenticated clinical research base, and the only EU Protected Geographical Indication among commercial cinnamon species — a combination not currently documented for any other commercial cinnamon species in peer-reviewed or regulatory literature.

SCIENTIFIC REFERENCES — PUBMED-LINKED WHERE AVAILABLE

[1]  Encyclopaedia Britannica. Cinnamon (Cinnamomum verum). Secondary historical reference. Documents Egyptian use (~2000 BCE), Pliny's silver valuation. britannica.com/plant/cinnamon  www.britannica.com

[2]  Rao PV & Gan SH. (2014). Cinnamon: A Multifaceted Medicinal Plant. Evidence-Based Complementary and Alternative Medicine 2014:642942. doi:10.1155/2014/642942. PubMed 24817901 · PMC4003790  PubMed  ·  PMC

[3]  Beheshti AS, et al. (2025). Molecular, cellular, and metabolic insights of cinnamon (C. zeylanicum) in diabetes. Naunyn-Schmiedeberg's Arch Pharmacol 398(4):3513–3526. doi:10.1007/s00210-024-03644-0. Majority of included studies preclinical. PubMed 39589531  PubMed

[4]  NCCIH. (2024). Cinnamon: Usefulness and Safety. U.S. NIH. States evidence does not clearly support cinnamon for any specific health condition; documents species ambiguity and coumarin differential. nccih.nih.gov/health/cinnamon  www.nccih.nih.gov

[5]  Muthukuda D, et al. (2025). Effects of C. zeylanicum extract on lipid profile, glucose levels and safety. PLoS ONE 20(1):e0317904. doi:10.1371/journal.pone.0317904. Primary endpoint (LDL-C) not met; secondary endpoint (FBS) statistically significant. PubMed 39854533 · PMC11759401  PubMed  ·  PMC

[6]  Mohammadabadi T & Jain R. (2024). Cinnamon: a nutraceutical supplement for the cardiovascular system. Arch Med Sci Atheroscler Dis 9:e72–e81. doi:10.5114/amsad/184245. Narrative review; mechanisms largely preclinical. PubMed 38846056 · PMC11155465  PubMed  ·  PMC

[7]  Nakhaee S, et al. (2023). Cinnamon and cognitive function: a systematic review of preclinical and clinical studies. Nutritional Neuroscience 27(2):132–146. doi:10.1080/1028415X.2023.2166436. 40 studies: 33 in vivo, 5 in vitro, 2 clinical. Human evidence insufficient for conclusions. PubMed 36652384  PubMed

[8]  Yanakiev S. (2020). Effects of Cinnamon (Cinnamomum spp.) in Dentistry: A Review. Molecules 25(18):4184. doi:10.3390/molecules25184184. In vitro antimicrobial activity; does not predict human clinical outcomes. PubMed 32932678 · PMC7571082  PubMed  ·  PMC

[9]  Blahová J & Svobodová Z. (2012). Assessment of Coumarin Levels in Ground Cinnamon Available in the Czech Retail Market. Scientific World Journal 2012:263851. 60-sample analysis: cassia 700–7,000+ mg/kg; C. verum below detection limit. PubMed 22593682 · PMC3385612  PubMed  ·  PMC

[10]  EFSA. (2004). Opinion on Coumarin. EFSA Journal 2(9):104. TDI: 0.1 mg coumarin/kg body weight/day. efsa.onlinelibrary.wiley.com  efsa.onlinelibrary.wiley.com

[11]  BfR. (2006). Coumarin in Cinnamon. Health Assessment No. 043/2006. Children identified as high-concern group. bfr.bund.de  www.bfr.bund.de

[12]  Oketch-Rabah HA, Marles RJ, Brinckmann JA. (2018). Cinnamon and Cassia Nomenclature Confusion. Clin Pharmacol Ther 104(3):435–445. doi:10.1002/cpt.1162. Species mislabelling makes clinical literature difficult to interpret. PubMed 29947417  PubMed

[13]  Department of Cinnamon Development, Government of Sri Lanka. (2023–2025). Official records; cultivation documented to 1400 BCE. cinnamon.gov.lk  cinnamon.gov.lk

[14]  European Union Commission. (2022). Implementing Regulation (EU) 2022/144. Ceylon Cinnamon Protected Geographical Indication. First enforceable provenance standard for any commercial cinnamon species. eur-lex.europa.eu  eur-lex.europa.eu

Editorial Standards & Compliance. This article is part of the Ceylon Nutritionals Science & Education Series. No statements constitute health claims under EU Regulation 1924/2006, the U.S. DSHEA, or equivalent frameworks. Mechanistic and preclinical findings are explicitly distinguished from human clinical outcomes throughout. NCCIH is incorporated as the primary balancing authority. EFSA and BfR regulatory documents provide the basis for coumarin safety statements. This content is not intended to replace professional medical advice, diagnosis, or treatment.