Cinnamomum

Cinnamomum: A Comprehensive Reference

1. Identity and Botanical Classification

Genus and Family: Cinnamomum is a large genus of aromatic trees and shrubs belonging to the family Lauraceae (the laurel family). The genus Cinnamomum comprises approximately 250 species, which occur in Eastern Asia, Australia, and the archipelago of the Pacific Ocean. The commercially and medicinally most significant members of the genus are a small number of species whose dried inner bark is traded globally as "cinnamon."

Commercially and medicinally relevant species:

• Cinnamomum verum J. Presl (synonym: Cinnamomum zeylanicum Blume) — "Ceylon cinnamon" or "true cinnamon." Native to Sri Lanka and Southern India, specifically the Malabar Coast, the cinnamon tree typically grows to a height of 7–10 m.
• Cinnamomum cassia (L.) J. Presl (synonym: Cinnamomum aromaticum Nees) — "Cassia cinnamon" or "Chinese cinnamon."
• Cinnamomum burmannii (Nees & T. Nees) Blume — "Indonesian cassia" or "Korintje cinnamon."
• Cinnamomum loureiroi — "Vietnamese cinnamon" or "Saigon cinnamon."

The four major commercially-viable species of cinnamon (Cinnamomum verum, C. cassia, C. burmannii, and C. loureiroi) have distinct flavour profiles, meaning that care should be taken when using this spice in the kitchen, especially given the naming confusion that exists between cinnamon and cassia.

Plant part used: Cinnamon is the name given to the bark of the thin lateral shoots taken from the foot of several tropical evergreen trees of the genus Cinnamomum. Trees tend to be harvested every two to three years. Beyond bark, leaves and roots are also used as sources of essential oil, each producing a chemically distinct profile.

Common Forms and Preparations: Cinnamon can be added to food in the form of whole or ground material or as extracts or oils obtained from leaves or bark. As supplements, it is available as capsules, powders, teas, tinctures, and standardized extracts. In research settings, both whole dried bark powder and water-soluble polyphenolic extracts have been used.

2. Historical and Traditional Use

Ancient and Near Eastern Cultures

Cinnamon is one of the oldest known spices and has been used in cooking and traditional herbal medicine for millennia. Egyptians imported it from China as early as 2000 B.C.E. and used the spice for embalming. Various Ancient Near Eastern cultures considered cinnamon sacred, and the Hebrew Bible mentions its use in anointing oils.

The emperor Nero, after the death of his wife Poppaea, reportedly burned a year's supply of cinnamon on her funeral pyre as a grand expression of mourning. Physicians like Dioscorides and Galen noted cinnamon's medicinal uses for digestion and respiratory conditions. In medieval times, cinnamon was an ingredient of medicines for sore throats and coughs.

Traditional Chinese Medicine (TCM)

Cinnamon has been widely used in Asia for more than 4,000 years. C. cassia bark, known in TCM as ròu guì, was used as a warming medicine. Cassia cinnamon was used to treat colds, boost circulation, and improve digestion — uses that continue in Traditional Chinese Medicine today. Cassia is prized in TCM for dispersing cold and invigorating the flow of "Qi" (energy).

Ayurvedic Medicine

In the ancient system of Ayurveda, cinnamon — known as "Twak" — played a vital role. Ayurvedic practitioners recognized its warming nature, which made it a valuable ingredient for balancing the body's doshas, particularly Vata and Kapha. Cinnamon was employed to aid digestion, alleviate respiratory ailments, and address menstrual discomfort. Traditional Ayurvedic formulations included mixing Darusita (cinnamon) powder with honey and ghee for digestive tonics (cinnamon ghrita).

Islamic and Persian Medicine

The 10th-century Persian physician Avicenna (Ibn Sina) included cinnamon in his famous medical texts, noting its warming properties and effectiveness in treating colds, coughs, and inflammation. Islamic traders were also instrumental in bringing cinnamon to Europe via Mediterranean ports, especially during the Crusades when cross-cultural contact surged.

European Trade and Colonial History

By the 16th century, Portuguese and Dutch explorers had discovered that the most coveted cinnamon came from the island of Ceylon (modern-day Sri Lanka). Cinnamon's value led to bloody battles and trade monopolies. The Portuguese controlled cinnamon exports from Ceylon until the Dutch ousted them in the 17th century. Eventually, the British took control in the 1800s, expanding cinnamon cultivation to other colonies.

3. Key Constituents and Active Compounds

Volatile (Essential Oil) Constituents

The chemical composition of Cinnamomum essential oils varies substantially by species and by plant part used. The main constituents of oils extracted from C. verum stem bark are trans-cinnamaldehyde (49.9–62.8%), eugenol, cinnamyl acetate, linalool, and benzyl benzoate. Oils extracted from the root bark contain camphor (up to 60%), 1,8-cineole, eugenol, terpinol, and cinnamaldehyde. The leaf oil contains eugenol (60–90%), cinnamaldehyde, linalool, and cinnamyl acetate. The fruit oil contains cadinene (30–40%), cadinol, and β-caryophyllene.

For C. verum bark essential oil specifically, cinnamaldehyde (59%), benzaldehyde (12%), and eugenol (5%) are the major compounds, while six minor constituents include α-phellandrene (1.1%), linalool (1.1%), benzoic acid (0.8%), β-caryophyllene (0.7%), linalyl acetate (0.6%), and benzyl cinnamate (0.6%).

The major constituent of both C. verum and C. cassia is cinnamaldehyde at 65–80% and 90% of the volatile oil, respectively. C. verum also contains o-methoxycinnamaldehyde; its volatile oil contains approximately 10% eugenol and terpenoids including linalool. In C. cassia, only a trace of eugenol is found.

Non-Volatile Constituents

Other minor constituents reported in cinnamon essential oil include cinnamic acid, phenolic acids, oligopolymeric procyanidins, pentacyclic diterpenes, cinnzeylanol, and its acetyl derivative cinnzeylanine, along with mannitol, xylose, arabinose, xylanose, glucose, and mucilage polysaccharides.

In terms of overall phytochemical complexity, approximately 306 chemical constituents have been separated and identified from the genus Cinnamomum, covering 111 terpenes, 44 phenylpropanoids, 51 lignans, 17 flavonoids, 53 aromatic compounds, 17 aliphatic compounds, four coumarins, and two steroids.

Coumarin — Species-Specific Distinction

A toxicologically important distinction exists between species regarding coumarin content. Most cinnamon on the market comes from China (Cinnamomum cassia) and contains significant amounts of coumarin (2.23 mg/g dry weight). True cinnamon (Cinnamomum zeylanicum) from Sri Lanka is a better alternative since its content of coumarin is negligible (<0.01 mg/g dry weight).

4. Mechanisms of Action

Insulin Sensitization and Glucose Metabolism

Multiple molecular mechanisms have been proposed to underlie cinnamon's metabolic effects. Preclinical studies indicate that cinnamon bioactives modulate glucose homeostasis through multiple complementary pathways, including inhibition of α-amylase and α-glucosidase, insulin signaling enhancement (PI3K/Akt, AMPK-GLUT4 translocation), hepatic glucose suppression, intestinal transporter downregulation, and gut microbiota modulation.

Water-soluble polyphenols — particularly type-A procyanidin polymers — are considered a primary active fraction. Water-soluble cinnamon extract (CE) and HPLC-purified cinnamon polyphenols (CP) with doubly linked procyanidin type-A polymers display insulin-like activity, and cinnamon improves glucose and lipid profiles of people with type 2 diabetes. Type-A procyanidins have been shown to exhibit approximately 20-fold insulin-mimetic potency in vitro.

Polyphenols of procyanidin type-A polymers in cinnamon also have insulin-like effects; they can increase the mRNA levels of insulin β-receptor (IR-β) and glucose transporter 4 (GLUT4, whose main function is to rapidly increase glucose intake under the condition of elevated insulin) in 3T3-L1 adipocytes. They also stimulate the autophosphorylation of insulin receptors, promote glucose absorption and glycogen biosynthesis, activate glycogen synthase, and inhibit glycogen synthase kinase.

A water extract of cinnamon (Cinnulin PF®) was observed to reduce blood glucose, plasma insulin, and soluble cluster of differentiation 36 (CD36), reported as a novel marker of insulin resistance. Cinnamon extracts also inhibited retinol-binding protein 4 (RBP4), a novel adipokine that contributes to insulin resistance in plasma and adipose tissues.

Anti-Inflammatory Mechanisms

The anti-inflammatory properties of cinnamon have been suggested to be derived via inhibition of nuclear factor kappa B (NF-κB) expression and consequently reduced production of proinflammatory cytokines, such as tumor necrosis factor (TNF), C-reactive protein (CRP), and interleukin-6 (IL-6). Anti-inflammatory effects occur through suppression of NF-κB, COX-2, and iNOS pathways.

Antioxidant Mechanisms

Most cinnamon studies in vitro and in vivo demonstrate significant antioxidant activity through multiple mechanisms, including reduction of malondialdehyde level (a lipid peroxidation marker), activation of transcription factor Nrf2, and synthesis of antioxidant enzymes. At the compound level, eugenol exhibited considerable NO radical scavenging (63%) and reducing abilities, while cinnamaldehyde showed comparatively better protective efficacy against lipid peroxidation in rat brain and kidney homogenates (up to 40%).

Antimicrobial Mechanisms

The spice oil components eugenol and cinnamaldehyde possess activity against both gram-positive and gram-negative bacteria. In broth media at 20°C, 5 mM eugenol or 30 mM cinnamaldehyde was bactericidal (>1-log reduction in CFU per milliliter in 1 hour) to Listeria monocytogenes. Cinnamaldehyde has been reported to inhibit the growth of Clostridium botulinum, Staphylococcus aureus, E. coli O157:H7, and Salmonella enterica serovar Typhimurium.

5. Scientific Evidence by Health Area

5.1 Glycemic Control and Type 2 Diabetes

This is the most extensively studied area for cinnamon supplementation in humans, and it has attracted numerous randomized controlled trials (RCTs) and meta-analyses.

Meta-analytic evidence: Although many RCTs have revealed benefits of cinnamon on type 2 diabetes mellitus, the effects on glycemic control remain inconclusive. Findings from 24 RCTs revealed that cinnamon supplementation had a statistically significant reduction in fasting blood sugar (SMD: −1.32; 95% CI: −1.77, −0.87, p < 0.001), Homeostatic Model Assessment for Insulin Resistance (SMD: −1.32), and hemoglobin A1C (SMD: −0.67; 95% CI: −1.18, −0.15, p = 0.011) compared with control.

The findings of a broader umbrella review indicate that cinnamon supplementation is significantly associated with improvements in fasting blood glucose and lipid profiles, with more pronounced effects observed in patients with diabetes and metabolic syndrome. Subgroup analyses indicated that higher doses (>1.5 g/day) and shorter intervention durations (≤2 months) were more likely to yield clinically meaningful improvements.

Limitations and heterogeneity: Supplementation with cinnamon can reduce serum levels of glucose with no changes in other glycemic parameters and anthropometric indices; however, due to high heterogeneity, findings should be interpreted with great caution. A key methodological issue is species conflation: chemical composition differences suggest that biological effects are also likely to differ between species, and analyses that combine results from different species of Cinnamomum may result in erroneous conclusions.

Study dosages reported: In a 2012 systematic review, 6 clinical trials met strict inclusion criteria, considering a total of 435 patients; follow-up ranged between 40 days and 4 months, with doses ranging from 1 g to 6 g per day. Clinical trials using whole spice or extracts (280–1000 mg/day) report consistent, modest reductions in fasting plasma glucose and HbA1c, most reliably in individuals with established glycemic dysregulation. In one specific trial, subjects consumed 1, 3, or 6 g of cinnamon per day for 40 days, with corresponding placebo groups.

Evidence strength: Moderate, based on multiple RCTs and meta-analyses showing statistically significant but modest effects, particularly on fasting blood glucose. High heterogeneity across studies, variable species used, and inconsistent effects on HbA1c limit definitive conclusions.

5.2 Lipid Profile and Cardiovascular Risk Markers

A recent meta-analysis showed that cinnamon significantly decreased blood triglyceride and total cholesterol levels but did not affect blood LDL-c and HDL-c levels. A separate systematic review examining lipid profiles found that for LDL, an intervention dose of less than 500 mg/day demonstrated a significant reduction (WMD: −10.26; 95% CI: −15.62, −4.90; p = 0.001), with a modest level of heterogeneity; in contrast, higher doses (≥500 mg/day) exhibited a non-significant increase in LDL levels.

Evidence strength: Moderate-to-low. Effects on triglycerides and total cholesterol appear more consistent across trials than effects on LDL or HDL cholesterol, which remain inconsistent and possibly dose-dependent.

5.3 Blood Pressure

Cinnamon's effect on blood pressure has also been evaluated in clinical trials and meta-analyses. An umbrella review of meta-analyses found that cinnamon might exert favorable effects on systolic blood pressure (ES = −2.36 mmHg; 95% CI: −3.86, −1.40) and diastolic blood pressure (ES = −1.65 mmHg; 95% CI: −2.41, −0.90). However, postulated hypotensive effects ascribed to cinnamon remain inconclusive. One analysis of eight studies including 582 participants suggested that cinnamon supplementation had beneficial effects only on diastolic blood pressure.

Evidence strength: Weak-to-moderate. Numerically small reductions in blood pressure have been reported, but clinical significance and mechanistic consistency remain uncertain.

5.4 Antioxidant and Anti-Inflammatory Effects

Preclinical and clinical studies have demonstrated that cinnamon possesses diverse pharmacological properties, including antioxidant, anti-inflammatory, antitumor, immunomodulatory, antidiabetic, and lipid-lowering effects. In the umbrella review, cinnamon shows potential in modulating insulin resistance, antioxidant capacity, and blood pressure regulation. Specifically on inflammatory markers, cinnamon was associated with improvements in total antioxidant capacity (WMD = 0.34; 95% CI: 0.04, 0.64) and interleukin-6 (WMD = −1.48; 95% CI: −2.96, −0.01).

Evidence strength: Moderate for in vitro and animal models; the human evidence on inflammatory biomarkers is limited and requires more dedicated RCTs.

5.5 Antimicrobial and Antifungal Properties

In vitro and in vivo studies on cinnamon extracts or its components (mainly cinnamaldehyde) revealed antifungal, anti-cardiovascular, anticancer, anti-inflammatory, antiulcer, antidiabetes, antiviral, antihypertensive, antioxidant, and cholesterol- and lipid-lowering effects. The antifungal activity of cinnamaldehyde, which is used as a vapor to treat respiratory tract mycoses, has been reported. Cinnamon acts against infectious fungi including Aspergillus niger, A. fumigatus, A. nidulans, A. flavus, and Candida albicans. Fluconazole-resistant strains showed sensitivity to cinnamon oils, suggesting usefulness against drug-resistant yeasts. Cinnamaldehyde disrupts fungal cell membranes and inhibits biofilm formation.

Evidence strength: Primarily preclinical (in vitro and animal). Human clinical trials specifically addressing antimicrobial outcomes are lacking, so this evidence remains preliminary.

5.6 Neuroprotective and Neurological Areas

Cinnamon has been investigated as a traditional medicine for possible use in controlling tumor growth, diabetes, Alzheimer's and Parkinson's diseases. However, further investigations are necessary to provide additional clinical evidence for the traditional uses of this spice against cancer and inflammatory, cardioprotective, and neurological disorders.

Evidence strength: Preliminary. Evidence from neurological and neurodegenerative disease contexts is largely limited to cell-culture or animal studies, with no established human clinical trial data supporting therapeutic use.

6. Body Systems and Health Areas Associated With Cinnamomum

• Metabolic and Endocrine System: Glycemic control, insulin sensitivity, insulin resistance (type 2 diabetes, prediabetes, metabolic syndrome)
• Cardiovascular System: Lipid-lowering effects (triglycerides, total cholesterol), blood pressure modulation, antioxidant effects on vascular tissue
• Digestive/Gastrointestinal System: Traditional use for dyspepsia, flatulence, nausea, and appetite stimulation; historically, cinnamon has been used medicinally for loss of appetite and dyspeptic complaints.
• Immune and Inflammatory System: Inhibition of NF-κB pathway, reduction of pro-inflammatory cytokines (TNF-α, IL-6, CRP)
• Microbial Defense: Antibacterial and antifungal activities, principally demonstrated in vitro and in animal models
• Respiratory System: Traditional use in TCM, Ayurveda, and medieval European medicine for coughs, colds, and sore throats
• Neurological System: Investigated preclinically for roles in Alzheimer's and Parkinson's disease; no established human clinical data

7. Dosage Forms and Reported Dosages in Studies

Cinnamon can be used whole, ground, as extract, or as essential oil. In the supplement and clinical research context, several dosage forms and ranges have been reported:

• Whole or ground bark powder: Doses of 1 to 6 g powdered cinnamon (approximately ¼ to 1 teaspoon) have been used in clinical studies.
• Standardized cassia extract: Doses of 200 to 300 mg cassia extract have been reported.
• Water-soluble polyphenolic extract (e.g., CinSulin®): One clinical trial used a commercially available spray-dried water extract of cinnamon containing more than 4% type-A procyanidin polyphenols in 250 mg capsules, taken twice a day.
• Dose range across clinical trials: Doses ranging from 1 g to 6 g per day have been used in RCTs with follow-up periods of 40 days to 4 months.
• Dose threshold for metabolic effects: Subgroup analyses suggest that higher doses (>1.5 g/day) and shorter intervention durations (≤2 months) may enhance metabolic benefits.

Dosage forms for traditional use include decoctions, powders mixed with honey or ghee (Ayurvedic preparations), infusions (teas), and topical essential oil applications.

8. Safety Considerations and Interactions

Coumarin Content and Hepatotoxicity

The most clinically important safety concern with cinnamon supplements relates to coumarin, a compound found primarily in cassia-type species. Interactions between coumarin, a chemical found in cassia cinnamon, and the liver have been reported. Consuming cassia cinnamon does not usually include enough coumarin to cause significant problems; however, some cassia cinnamon products contain high levels of coumarin. Prolonged use of cassia cinnamon could be an issue for sensitive people, such as those with liver disease.

Coumarin is a flavouring substance contained in relatively high concentrations in cinnamon varieties collectively known as "Cassia cinnamon." In especially sensitive persons, even comparatively small quantities of coumarin can cause liver damage, although the effect is usually reversible. In mild cases, this leads to an increase of liver enzymes in the blood. In severe cases, it results in inflammation of the liver which can manifest as jaundice.

A published case report documented a rare case of herb-induced liver injury (HILI) in a 34-year-old female, attributed to prolonged ingestion of cinnamon for weight loss purposes. This case report establishes a probable causal relationship between cinnamon exposure and HILI through the systematic application of multiple ADR causality assessment tools.

True cinnamon (Cinnamomum zeylanicum) from Sri Lanka is a better alternative for long-term supplementation, since its content of coumarin is negligible (<0.01 mg/g dry weight). For cinnamon-containing foods, new maximum permissible coumarin levels have been in place in the European Union since 2011.

Pregnancy

Some studies of the use of Ceylon and cassia cinnamon during pregnancy suggest it is safe in amounts commonly found in foods, but Ceylon cinnamon in larger amounts during pregnancy is considered unsafe. Animal studies have indicated that the constituent cinnamaldehyde increases the risk of foetal abnormalities at larger doses.

Topical Use

Some types of topical cinnamon oil or powder may cause skin irritation or contact dermatitis, according to reports.

Drug Interactions

According to research partially funded by the National Center for Complementary and Integrative Health, there are theoretical reasons to suspect that some components of cinnamon may interact with an anticancer medicine or nicotine. Because cinnamon can lower blood glucose, additive effects should be considered when taken alongside antidiabetic drugs. Cinnamon is generally well tolerated, and gastrointestinal side effects are the most common.

Regulatory and Quality Considerations

Consumers who take cinnamon-based food supplements should be aware that such products may contain high quantities of cassia cinnamon. The German Federal Institute for Risk Assessment (BfR) recommends moderate consumption of cassia cinnamon.

9. Research Limitations and Evidence Gaps

Across the body of clinical research on Cinnamomum, a number of consistent limitations reduce confidence in the existing evidence base:

• Species conflation: Many clinical trials and meta-analyses group different Cinnamomum species together, despite established chemical differences between them.
• Heterogeneity of preparations: Whole powder, aqueous extracts, and essential oils each have different active compound profiles, making cross-trial comparisons difficult.
• Short follow-up periods: Most RCTs have limited durations of 40 days to 4 months, providing little data on long-term safety or sustained efficacy.
• Small sample sizes: Many individual trials involve small numbers of participants, limiting statistical power.
• Future research should focus on well-designed randomized controlled trials with extended follow-up periods and standardized species identification and extract characterization.

References

• Frontiers in Pharmacology / PMC: "Cinnamomum Species: Bridging Phytochemistry Knowledge, Pharmacological Properties and Toxicological Safety for Health Benefits" (2021)
• ScienceDirect Topics: Cinnamomum — Overview of Chemical Constituents
• ScienceDirect: "Cinnamon: The historic spice, medicinal uses, and flavour chemistry" (2023)
• ScienceDirect: "Revisiting an ancient spice with medicinal purposes: Cinnamon" (2017)
• PubMed: "A Systematic Review Evaluating Cinnamon's Effects on Glucose Utilizing a Ranking System to Assess Bias and Study Quality" (2024)
• PMC: "The effects of cinnamon on patients with metabolic diseases: an umbrella review of meta-analyses of randomized controlled trials" (2025)
• Frontiers in Physiology: "Efficacy of cinnamon supplementation on glycolipid metabolism in T2DM diabetes: A meta-analysis and systematic review" (2022)
• PubMed: "The impact of cinnamon on anthropometric indices and glycemic status in patients with type 2 diabetes: A systematic review and meta-analysis" (2019)
• PubMed: "The effect of cinnamon supplementation on glycemic control in patients with type 2 diabetes mellitus: An updated systematic review and dose-response meta-analysis of RCTs" (2023)
• PMC: "Cinnamon Use in Type 2 Diabetes: An Updated Systematic Review and Meta-Analysis" (2013)
• PubMed: "Pharmacological activities of cinnamaldehyde and eugenol: antioxidant, cytotoxic and anti-leishmanial studies" (2017)
• PMC: "Mechanisms of Bactericidal Action of Cinnamaldehyde against Listeria monocytogenes and of Eugenol against L. monocytogenes and Lactobacillus sakei"
• NIH/NCCIH: "Cinnamon: Usefulness and Safety"
• German Federal Institute for Risk Assessment (BfR): "FAQ on coumarin in cinnamon and other foods"
• PMC: "Coumarin-Induced Hepatotoxicity: A Narrative Review" (2022)
• PMC: "Probable Cinnamon-Induced Mixed Hepatocellular-Cholestatic Liver Injury in a Young Woman: A Case Report" (2025)
• PMC: "The Relation between Hepatotoxicity and the Total Coumarin Intake from Traditional Japanese Medicines Containing Cinnamon Bark" (2016)
• PMC: "Cinnamon effects on blood pressure and metabolic profile: A double-blind, randomized, placebo-controlled trial in patients with stage 1 hypertension" (2021)
• PubMed: "Effect of cinnamon supplementation on blood pressure, oxidative stress, and inflammatory biomarkers in adults: An umbrella review" (2024)
• PMC: "Effects of Cinnamon Supplementation on Lipid Profile: A Systematic Review and Meta-Analysis of Randomized Controlled Trials" (2024)
• PMC: "Cinnamon: A Multifaceted Medicinal Plant" (2014)
• PMC: "Beneficial Effects of Cinnamon on the Metabolic Syndrome, Inflammation, and Pain, and Mechanisms Underlying These Effects – A Review" (2014)
• PMC: "Cinnamon: an aromatic condiment applicable to chronic kidney disease" (2023)
• PMC: "Cinnamon extract lowers glucose, insulin and cholesterol in people with elevated serum glucose" (2016)
• PubMed: "Cinnamon extract and polyphenols affect the expression of tristetraprolin, insulin receptor, and glucose transporter 4 in mouse 3T3-L1 adipocytes" (2007)
• PMC: "Cinnamon: Potential Role in the Prevention of Insulin Resistance, Metabolic Syndrome, and Type 2 Diabetes" (2010)
• ScienceDirect: "A critical appraisal of anti-hyperglycemic mechanisms, matrix-dependent bioavailability, and species-stratified safety of Cinnamomum spp. as functional food ingredients" (2026)
• American Botanical Council (HerbalGram): "Cinnamon – A Bit of History"