Ceylon Cinnamon

The inner bark is taken as a powder, an infusion or a decoction, and as a tincture within compound formulas.

Western practice treats cinnamon as a warming aromatic with three actions. It is a carminative and digestive stimulant for sluggish, cold digestion, poor appetite and wind. It is a circulatory stimulant for cold extremities. And it is astringent, the basis of its older use for diarrhoea and for checking bleeding.

It is rarely used alone. It warms a formula and makes bitter or cold remedies easier to take.

Ayurveda classes cinnamon as warming, pungent and stimulating.

It is given for weak digestion, poor circulation, respiratory congestion, fatigue and sluggish metabolism, the pattern Ayurveda links to excess kapha and a cold constitution.

In traditional medicine cinnamon is a remedy for respiratory, digestive and gynaecological complaints ^{8Reference 8Ranasinghe et al. · 2013Systematic reviewMedicinal properties of ‘true’ cinnamon (Cinnamomum zeylanicum): a systematic reviewView study →}. It is also used for asthma, bronchitis, diarrhoea, headache, inflammation and heart complaints ^{29Reference 29Singh et al. · 2021ReviewPhytochemical and pharmacological review of Cinnamomum verum JView study →}.

A 2025 randomised, double-blind, placebo-controlled trial in Sri Lanka enrolled 210 adults with type 2 diabetes. They took a standardised C. verum extract at 250 mg or 500 mg, or a placebo, and 186 completed four months ^{3Reference 3Ranasinghe et al. · 2025RCTEfficacy and safety of Cinnamomum zeylanicum (Ceylon cinnamon) for diabetes mellitus: a randomised, double-blind, placebo-controlled clinical trial (RCT, n=210)View study →}.

Fasting glucose and HbA1c fell significantly from baseline in both extract groups, and regression analysis identified the extract as a significant predictor of both changes. Insulin resistance fell and β-cell function improved in the 500 mg group ^{3Reference 3Ranasinghe et al. · 2025RCTEfficacy and safety of Cinnamomum zeylanicum (Ceylon cinnamon) for diabetes mellitus: a randomised, double-blind, placebo-controlled clinical trial (RCT, n=210)View study →}. The authors hold a patent on the extract ^{3Reference 3Ranasinghe et al. · 2025RCTEfficacy and safety of Cinnamomum zeylanicum (Ceylon cinnamon) for diabetes mellitus: a randomised, double-blind, placebo-controlled clinical trial (RCT, n=210)View study →}.

In a separate 2025 trial of 150 adults with raised LDL, 1,000 mg a day of extract lowered fasting glucose by about 8.6 mg/dL more than placebo, with the largest fall in people with type 2 diabetes ^{4Reference 4Muthukuda et al. · 2025RCTEffects of Cinnamomum zeylanicum (Ceylon cinnamon) extract on lipid profile, glucose levels and safety in adults: a randomised, double-blind, placebo-controlled trial (RCT, n=150)View study →}.

A 2012 systematic review found no human C. verum trials at that time. In the laboratory, C. zeylanicum inhibits α-amylase and α-glucosidase, increases GLUT4-mediated glucose uptake and potentiates insulin-receptor activity ^{6Reference 6Ranasinghe et al. · 2012Meta-analysisEfficacy and safety of ‘true’ cinnamon (Cinnamomum zeylanicum) as a pharmaceutical agent in diabetes: a systematic review and meta-analysisView study →}. In rats, the extract lowered fasting glucose only in diabetic animals, not healthy ones ^{7Reference 7Ranasinghe et al. · 2012AnimalEffects of Cinnamomum zeylanicum (Ceylon cinnamon) on blood glucose and lipids in a diabetic and healthy rat model — animal studyView study →}.

Meta-analyses of cinnamon in general find lower fasting glucose with a smaller and less reliable effect on HbA1c ^{10,11,13Reference 10Allen et al. · 2013Meta-analysisCinnamon use in type 2 diabetes: an updated systematic review and meta-analysis (10 RCTs)View study →Reference 11Moridpour et al. · 2024Meta-analysisThe effect of cinnamon supplementation on glycemic control in type 2 diabetes: an updated systematic review and dose-response meta-analysis of randomised controlled trialsView study →Reference 13Deyno et al. · 2019Meta-analysisEfficacy and safety of cinnamon in type 2 diabetes and pre-diabetes: a meta-analysis and meta-regression of randomised controlled trialsView study →}. An early meta-analysis of five trials found no significant effect at all ^{12Reference 12Baker et al. · 2008Meta-analysisEffect of cinnamon on glucose control and lipid parameters — meta-analysis of randomised controlled trials (null result)View study →}.

Gap: one positive C. verum trial, of a standardised extract rather than the spice, and no data beyond four months.

Pectic polysaccharides from the bark (an arabinogalactan, a galacturonic-acid fraction and a glucan) showed radical-scavenging activity in FRAP and DPPH assays ^{16Reference 16Ghosh et al. · 2015In vitroAntioxidant activity and structural features of Cinnamomum zeylanicum — in vitro study of bark polysaccharidesView study →}. The volatile oils from different parts of the tree also show antioxidant activity ^{17Reference 17Jayaprakasha et al. · 2011ReviewChemistry, biogenesis, and biological activities of Cinnamomum zeylanicum — reviewView study →}.

Gap: no C. verum-specific human antioxidant trial. Scavenging in a test tube does not establish an antioxidant effect in the body.

In human THP-1 monocytes, a methanol extract of C. verum lowered reactive oxygen species by reducing NOX2, and blocked the PKCδ/JNK/AP-1/NF-κB pathway ^{18Reference 18Kim et al. · 2023In vitroCinnamomum verum extract inhibits NOX2/ROS and PKCδ/JNK/AP-1/NF-κB pathway-mediated inflammatory response in PMA-stimulated THP-1 monocytes — in vitro studyView study →}. The extract and two of its components, cinnamic acid and coumarin, reduced IL-1β, IL-8, CCL5 and COX-2 ^{18Reference 18Kim et al. · 2023In vitroCinnamomum verum extract inhibits NOX2/ROS and PKCδ/JNK/AP-1/NF-κB pathway-mediated inflammatory response in PMA-stimulated THP-1 monocytes — in vitro studyView study →}.

Leaf extracts inhibited COX-1 and COX-2 and scavenged nitric oxide and superoxide in vitro ^{19Reference 19Abeysekera et al. · 2022In vitroAnti-inflammatory, cytotoxicity and antilipidemic properties: novel bioactivities of true cinnamon (Cinnamomum zeylanicum Blume) leaf — in vitro studyView study →}. A bark extract inhibited protein denaturation in test-tube assays ^{21Reference 21Ul Hasnain et al. · 2024AnimalAnti-inflammatory, antidiabetic and hypolipidemic potential of Cinnamomum verum JView study →}.

In people, a meta-analysis of six trials (285 participants) found cinnamon lowered serum C-reactive protein by about 0.8 mg/L ^{20Reference 20Vallianou et al. · 2019Meta-analysisEffect of cinnamon (Cinnamomum zeylanicum) supplementation on serum C-reactive protein concentrations: a meta-analysis and systematic review of randomised controlled trialsView study →}.

Gap: no trial has measured an inflammatory outcome using C. verum in people.

A 2025 trial designed for this question gave 150 adults with raised LDL 1,000 mg a day of standardised extract or placebo for 12 weeks ^{4Reference 4Muthukuda et al. · 2025RCTEffects of Cinnamomum zeylanicum (Ceylon cinnamon) extract on lipid profile, glucose levels and safety in adults: a randomised, double-blind, placebo-controlled trial (RCT, n=150)View study →}. ⚠ LDL was lower with the extract, but the difference (about 6 mg/dL) was not significant ^{4Reference 4Muthukuda et al. · 2025RCTEffects of Cinnamomum zeylanicum (Ceylon cinnamon) extract on lipid profile, glucose levels and safety in adults: a randomised, double-blind, placebo-controlled trial (RCT, n=150)View study →}. The trial was funded by a spice company ^{4Reference 4Muthukuda et al. · 2025RCTEffects of Cinnamomum zeylanicum (Ceylon cinnamon) extract on lipid profile, glucose levels and safety in adults: a randomised, double-blind, placebo-controlled trial (RCT, n=150)View study →}.

In the phase I trial, total and LDL cholesterol fell significantly over three months in 30 healthy adults ^{5Reference 5Ranasinghe et al. · 2017Clinical trialEvaluation of pharmacodynamic properties and safety of Cinnamomum zeylanicum (Ceylon cinnamon) in healthy adults — phase I clinical trialView study →}.

Class-level meta-analyses report falls in total cholesterol, LDL and triglycerides and a small rise in HDL, with high heterogeneity ^{10,14Reference 10Allen et al. · 2013Meta-analysisCinnamon use in type 2 diabetes: an updated systematic review and meta-analysis (10 RCTs)View study →Reference 14Jafari et al. · 2025Meta-analysisThe effect of cinnamon supplementation on cardiovascular risk factors in adults: a GRADE-assessed systematic review, dose-response and meta-analysis of randomised controlled trialsView study →}. In the laboratory, C. verum leaf extract inhibits HMG-CoA reductase, pancreatic lipase and cholesterol micelle formation ^{19Reference 19Abeysekera et al. · 2022In vitroAnti-inflammatory, cytotoxicity and antilipidemic properties: novel bioactivities of true cinnamon (Cinnamomum zeylanicum Blume) leaf — in vitro studyView study →}. In rats on a high-fat, high-sugar diet, a bark extract improved lipids ^{21Reference 21Ul Hasnain et al. · 2024AnimalAnti-inflammatory, antidiabetic and hypolipidemic potential of Cinnamomum verum JView study →}.

Gap: the trial built to answer this question found no significant effect on LDL ^{4Reference 4Muthukuda et al. · 2025RCTEffects of Cinnamomum zeylanicum (Ceylon cinnamon) extract on lipid profile, glucose levels and safety in adults: a randomised, double-blind, placebo-controlled trial (RCT, n=150)View study →}.

A phase I trial of C. verum water extract enrolled 30 healthy Sri Lankan adults. The dose was raised each month from 85 to 250 to 500 mg over three months ^{5Reference 5Ranasinghe et al. · 2017Clinical trialEvaluation of pharmacodynamic properties and safety of Cinnamomum zeylanicum (Ceylon cinnamon) in healthy adults — phase I clinical trialView study →}.

Systolic and diastolic pressure fell significantly in the first month, and the fall held throughout. Liver and kidney function stayed normal ^{5Reference 5Ranasinghe et al. · 2017Clinical trialEvaluation of pharmacodynamic properties and safety of Cinnamomum zeylanicum (Ceylon cinnamon) in healthy adults — phase I clinical trialView study →}.

A 2021 meta-analysis of eight trials found cinnamon lowered diastolic pressure. Systolic pressure fell only in trials lasting eight weeks or more ^{15Reference 15Ghavami et al. · 2021Meta-analysisWhat is the impact of cinnamon supplementation on blood pressure? A systematic review and meta-analysis of randomised controlled trialsView study →}. A 2025 meta-analysis of 49 studies found a significant fall in diastolic pressure ^{14Reference 14Jafari et al. · 2025Meta-analysisThe effect of cinnamon supplementation on cardiovascular risk factors in adults: a GRADE-assessed systematic review, dose-response and meta-analysis of randomised controlled trialsView study →}.

Gap: no placebo-controlled C. verum trial has taken blood pressure as its main outcome.

Ceylon bark oil, about 69% (E)-cinnamaldehyde, was strongly active against 21 bacteria and 4 Candida species in vitro ^{22Reference 22Unlu et al. · 2010In vitroComposition, antimicrobial activity and in vitro cytotoxicity of essential oil from Cinnamomum zeylanicum Blume — in vitro studyView study →}.

The oil was also active against 50 multidrug-resistant Shigella isolates ^{23Reference 23Akrami et al. · 2021In vitroIn vitro evaluation of the antibacterial effects of Cinnamomum zeylanicum essential oil against clinical multidrug-resistant Shigella isolatesView study →}. Loaded into solid lipid nanoparticles, it inhibited multidrug-resistant E. coli ^{24Reference 24Nemattalab et al. · 2022In vitroFormulation of Cinnamomum verum oil-loaded solid lipid nanoparticles and evaluation of antibacterial activity against multidrug-resistant Escherichia coli — in vitro studyView study →}.

Cinnamaldehyde and eugenol are thought to act by disrupting microbial membranes and enzymes.

Gap: the active concentrations belong to the concentrated oil. Bark tea or powder does not reach them in the body.

In mice, C. verum bark water extract (200 mg/kg a day for 14 days before a toxic dose of acetaminophen) lowered serum ALT, AST, creatinine and urea ^{25Reference 25Hussain et al. · 2019AnimalProtective effects of Cinnamomum zeylanicum L. (Darchini) in acetaminophen-induced oxidative stress, hepatotoxicity and nephrotoxicity — mouse modelView study →}. It limited liver and kidney damage and restored total antioxidant capacity ^{25Reference 25Hussain et al. · 2019AnimalProtective effects of Cinnamomum zeylanicum L. (Darchini) in acetaminophen-induced oxidative stress, hepatotoxicity and nephrotoxicity — mouse modelView study →}.

Gap: one animal model against one toxin, with no human data.

Bark extract at 200 and 400 mg/kg for 21 days reversed scopolamine-induced memory impairment in rats. It lowered brain malondialdehyde and raised glutathione ^{26Reference 26Jain et al. · 2015AnimalEffect of Cinnamomum zeylanicum extract on scopolamine-induced cognitive impairment and oxidative stress — rat modelView study →}.

In vitro, C. verum bark oil was the most potent of six oils from Iranian traditional medicine at inhibiting acetylcholinesterase and butyrylcholinesterase. It also inhibited BACE1, the enzyme that starts amyloid formation ^{27Reference 27Saeedi et al. · 2022In vitroCinnamomum verum JView study →}. It did not protect PC12 cells against amyloid-β toxicity ^{27Reference 27Saeedi et al. · 2022In vitroCinnamomum verum JView study →}.

Gap: animal and enzyme-assay evidence only, and no human memory trial of C. verum exists.

Ceylon cinnamon leaf extracts slowed growth of breast (MCF7), liver (HepG2) and endometrial (AN3CA) cancer cells in vitro ^{19Reference 19Abeysekera et al. · 2022In vitroAnti-inflammatory, cytotoxicity and antilipidemic properties: novel bioactivities of true cinnamon (Cinnamomum zeylanicum Blume) leaf — in vitro studyView study →}.

In rats with benzene-induced leukaemia, C. zeylanicum given with doxorubicin gave better results than either alone, through effects on the TRAIL and NF-κB pathways ^{28Reference 28Bukhari et al. · 2022AnimalCombined efficacy of Cinnamomum zeylanicum and doxorubicin against leukaemia through regulation of TRAIL and NF-κB pathways — rat modelView study →}.

Gap: the cell-line concentrations are not reachable by eating the bark, and the animal study tested cinnamon alongside doxorubicin rather than alone.

Coumarin. Ceylon cinnamon contains only traces of coumarin, the compound that limits how much cassia can safely be taken ^{2,32Reference 2Abraham et al. · 2010ReviewToxicology and risk assessment of coumarin: focus on human data — reviewView study →Reference 32Wang et al. · 2013Cassia cinnamon as a source of coumarin in cinnamon-flavored food and food supplements in the United States — analytical studyView study →}.

Reported adverse effects. A systematic review of cinnamon adverse events found they were mostly stomach upset and allergic reactions, usually self-limiting. It advised clinical monitoring for larger medicinal doses or long-term use ^{30Reference 30Hajimonfarednejad et al. · 2019Systematic reviewCinnamon: a systematic review of adverse eventsView study →}.

In the phase I trial, two of 30 participants stopped because of indigestion. There were no serious adverse effects, and liver function and blood clotting were unaffected ^{5Reference 5Ranasinghe et al. · 2017Clinical trialEvaluation of pharmacodynamic properties and safety of Cinnamomum zeylanicum (Ceylon cinnamon) in healthy adults — phase I clinical trialView study →}.

Diabetes medicines. Concentrated extract lowered fasting glucose and HbA1c in the 2025 diabetes trial ^{3Reference 3Ranasinghe et al. · 2025RCTEfficacy and safety of Cinnamomum zeylanicum (Ceylon cinnamon) for diabetes mellitus: a randomised, double-blind, placebo-controlled clinical trial (RCT, n=210)View study →}. It may add to the effect of diabetes medicines, so glucose should be monitored when the two are combined.

Essential oil and skin. The concentrated oil irritates skin and mucous membranes and should never be swallowed undiluted. Cinnamaldehyde is a recognised contact allergen, which matters mainly for the oil and for skin contact rather than for the spice.

Drug metabolism. In 16 healthy adults, Ceylon cinnamon taken at 2 g three times a day for five days did not change blood levels of nicotine or the breast-cancer drug letrozole, both cleared by the liver enzyme CYP2A6 ^{37Reference 37Nguyen et al. · 2026Pharmacokinetic evaluation of a cinnamon product on CYP2A6 substrate drugs: application of a novel tool involving the nicotine metabolite ratio — human pharmacokinetic studyView study →}.

In laboratory tests, cinnamaldehyde and the bark oil weakly inhibited CYP1A2 and CYP2C9, and had no effect on CYP3A4 or CYP2D6 ^{38Reference 38Husain et al. · 2025In vitroEvaluation of bioaccessibility, metabolic clearance and interaction with xenobiotic receptors (PXR and AhR) of cinnamaldehyde — in vitro studyView study →}.