Cassia Cinnamon

In Chinese medicine the dried stem bark is rou gui (肉桂). The Chinese Pharmacopoeia classes it as pungent and sweet in taste and hot in nature, entering the Kidney, Spleen, Heart and Liver channels ^{26Reference 26Chinese Pharmacopoeia Commission · 2020ReviewPharmacopoeia of the People’s Republic of China, Vol}.

It is intensely warming. It is used to warm the interior, dispel cold and restore depleted yang.

The Shennong Bencao Jing used it for arthritis, the Mingyi Bielu recorded it as a pain reliever, and the Yaoxing Lun used it for abdominal pain and painful periods ^{24Reference 24Zhang C et al. · 2019ReviewCinnamomum cassia Presl: A Review of Its Traditional Uses, Phytochemistry, Pharmacology and Toxicology — reviewView study →}. Today it is a common Chinese medicine for kidney disease, painful periods, menstrual disorders and diabetes ^{24Reference 24Zhang C et al. · 2019ReviewCinnamomum cassia Presl: A Review of Its Traditional Uses, Phytochemistry, Pharmacology and Toxicology — reviewView study →}.

It is given for cold hands and feet, weakness, abdominal pain, a weak lower back, poor circulation and cold digestive conditions. More than 500 Chinese formulas contain it ^{24Reference 24Zhang C et al. · 2019ReviewCinnamomum cassia Presl: A Review of Its Traditional Uses, Phytochemistry, Pharmacology and Toxicology — reviewView study →}.

Cinnamon twig, gui zhi, is a separate medicine used to release the exterior and harmonise circulation.

Western herbalists treat cinnamon as a warming circulatory stimulant, an aromatic digestive and an antimicrobial spice.

It is given for poor circulation, cold digestion, bloating, nausea, diarrhoea, sluggish digestion and chest congestion that comes with a chill.

The German Commission E approved Chinese cinnamon bark (Cinnamomi cassiae cortex) for loss of appetite and for dyspeptic complaints such as bloating, flatulence and mild cramping of the gut ^{25Reference 25Blumenthal M et al. · 1998ReviewCinnamon, Chinese (Cinnamomi cassiae cortex)}.

The bark was also used in preserving preparations.

A 2024 dose-response meta-analysis of 24 RCTs in type 2 diabetes found significant reductions in fasting blood sugar, HOMA-IR (insulin resistance) and HbA1c, with no significant change in fasting insulin ^{1Reference 1Moridpour AH et al. · 2024Meta-analysisThe effect of cinnamon supplementation on glycemic control in patients with type 2 diabetes mellitus: an updated systematic review and dose-response meta-analysis of randomized controlled trials — [meta-analysis]View study →}.

A 2019 meta-analysis of 16 trials found lower fasting glucose (by about 0.5 mmol/L) and HOMA-IR, with no significant change in HbA1c ^{3Reference 3Deyno S et al. · 2019Meta-analysisEfficacy and safety of cinnamon in type 2 diabetes mellitus and pre-diabetes patients: a meta-analysis and meta-regression — [meta-analysis]View study →}.

A 2025 meta-analysis of 28 RCTs (3,054 patients) found fasting glucose fell by about 15 mg/dL, HbA1c by about 0.6% and HOMA-IR overall. In the trials that used capsules, fasting glucose fell by about 18 mg/dL and post-meal glucose by about 45 mg/dL, and only doses of 2 g a day or less lowered HbA1c ^{4Reference 4de Moura SL et al. · 2025Meta-analysisEffects of cinnamon supplementation on metabolic biomarkers in individuals with type 2 diabetes: a systematic review and meta-analysis — [meta-analysis]View study →}.

In prediabetes, a 12-week double-blind trial gave 54 adults 500 mg of cinnamon or placebo three times a day. Fasting glucose rose on placebo but stayed stable on cinnamon, a difference of 5 mg/dL, and glucose tolerance improved ^{28Reference 28Romeo GR et al. · 2020RCTInfluence of Cinnamon on Glycemic Control in Individuals With Prediabetes: A Randomized Controlled TrialView study →}.

⚠ Earlier syntheses disagree on HbA1c. A 2013 meta-analysis of 10 RCTs (543 patients) found fasting glucose fell by about 25 mg/dL, but HbA1c did not change significantly, and heterogeneity was high (I² 66–95%) ^{2Reference 2Allen RW et al. · 2013Meta-analysisCinnamon use in type 2 diabetes: an updated systematic review and meta-analysis — [meta-analysis]View study →}.

The 2012 Cochrane review of 10 trials (577 participants) found the effect on fasting glucose inconclusive and no significant difference in HbA1c. Most of its trials used C. cassia at a mean of 2 g a day, and nearly all were at high or unclear risk of bias. It concluded there was insufficient evidence to support cinnamon for diabetes ^{5Reference 5Leach MJ · 2012Systematic reviewCinnamon for diabetes mellitus — [systematic review]View study →}.

Doses in the trials ranged from 120 mg a day of extract to 6 g a day of powdered bark ^{2Reference 2Allen RW et al. · 2013Meta-analysisCinnamon use in type 2 diabetes: an updated systematic review and meta-analysis — [meta-analysis]View study →}.

Gap: HbA1c does not move consistently, and no trial has measured long-term diabetes outcomes.

A 2017 meta-analysis of 13 RCTs (750 participants) found significant falls in triglycerides (about 24 mg/dL) and total cholesterol (about 14 mg/dL), with no significant effect on LDL or HDL ^{6Reference 6Maierean SM et al. · 2017Meta-analysisThe effects of cinnamon supplementation on blood lipid concentrations: a systematic review and meta-analysis — [meta-analysis]View study →}.

A 2022 dose-response meta-analysis of 35 trials in metabolic disease found falls in total cholesterol (about 12 mg/dL), triglycerides (about 16 mg/dL) and LDL (about 6 mg/dL), and a small rise in HDL. The effects were clearest at doses of 1.5 g a day or less ^{7Reference 7Kutbi EH et al. · 2022Meta-analysisThe beneficial effects of cinnamon among patients with metabolic diseases: a systematic review and dose-response meta-analysis of randomized controlled trials — [meta-analysis]View study →}. The 2013 diabetes meta-analysis also found total cholesterol, LDL and triglycerides fell while HDL rose ^{2Reference 2Allen RW et al. · 2013Meta-analysisCinnamon use in type 2 diabetes: an updated systematic review and meta-analysis — [meta-analysis]View study →}.

A 2023 umbrella analysis of eleven meta-analyses found improvements in total cholesterol, LDL and HDL, but not triglycerides, with the clearest benefit in PCOS ^{8Reference 8Sarmadi B et al. · 2023Meta-analysisThe effect of cinnamon consumption on lipid profile, oxidative stress, and inflammation biomarkers in adults: an umbrella meta-analysis of randomized controlled trials — [meta-analysis]View study →}.

The analyses disagree on which lipid fractions change. Effect sizes are small throughout.

A 2020 meta-analysis of 9 RCTs (641 adults) found systolic pressure fell by about 5.2 mmHg and diastolic by about 3.4 mmHg ^{9Reference 9Hadi A et al. · 2020Meta-analysisThe effect of cinnamon supplementation on blood pressure in adults: a systematic review and meta-analysis of randomized controlled trials — [meta-analysis]View study →}.

⚠ The fall was significant only when cinnamon was taken at 2 g a day or less, for longer than eight weeks, and by people with a BMI of 30 or more ^{9Reference 9Hadi A et al. · 2020Meta-analysisThe effect of cinnamon supplementation on blood pressure in adults: a systematic review and meta-analysis of randomized controlled trials — [meta-analysis]View study →}.

A second 2020 meta-analysis, of 9 studies in type 2 diabetes, also found significant falls in systolic and diastolic pressure ^{10Reference 10Jamali N et al. · 2020Meta-analysisEffect of cinnamon supplementation on blood pressure and anthropometric parameters in patients with type 2 diabetes: a systematic review and meta-analysis of clinical trials — [meta-analysis]View study →}.

Gap: the trials are few and short, and none measured a cardiovascular outcome.

A 2020 meta-analysis of five small trials in polycystic ovary syndrome found significant falls in fasting blood sugar, fasting insulin, HOMA-IR, LDL, total cholesterol and triglycerides, and a rise in HDL. Body weight and BMI did not change significantly ^{15Reference 15Heydarpour F et al. · 2020Meta-analysisEffects of cinnamon on controlling metabolic parameters of polycystic ovary syndrome: a systematic review and meta-analysis — [meta-analysis]View study →}.

The umbrella meta-analysis also found the lipid benefit clearest in PCOS ^{8Reference 8Sarmadi B et al. · 2023Meta-analysisThe effect of cinnamon consumption on lipid profile, oxidative stress, and inflammation biomarkers in adults: an umbrella meta-analysis of randomized controlled trials — [meta-analysis]View study →}.

These trials measured metabolic markers. They did not report on ovulation or androgens.

Cassia oil and cinnamaldehyde inhibited a range of bacteria, Candida yeasts, moulds and skin fungi in vitro, with minimum inhibitory concentrations of 75–600 µg/mL for bacteria ^{11Reference 11Ooi LS et al. · 2006In vitroAntimicrobial activities of cinnamon oil and cinnamaldehyde from the Chinese medicinal herb Cinnamomum cassia — [in vitro]View study →}.

Cinnamaldehyde inhibited Helicobacter pylori, the bacterium behind many ulcers and gastritis, at 8–16 µg/mL in vitro, including antibiotic-resistant strains ^{12Reference 12Li CY et al. · 2024In vitroCinnamaldehyde: an effective component of Cinnamomum cassia inhibiting Helicobacter pylori — [in vitro and mouse in vivo]View study →}. In a mouse model of acute gastritis, cinnamaldehyde combined with a proton-pump inhibitor worked better than standard triple therapy ^{12Reference 12Li CY et al. · 2024In vitroCinnamaldehyde: an effective component of Cinnamomum cassia inhibiting Helicobacter pylori — [in vitro and mouse in vivo]View study →}.

Cassia is widely used for dyspepsia, wind, diarrhoea and vomiting ^{13Reference 13Muhammad JS et al. · 2015In vitroAnti-inflammatory effect of cinnamaldehyde in Helicobacter pylori induced gastric inflammation — [in vitro]View study →}.

Gap: the active concentrations belong to the essential oil or purified cinnamaldehyde, not bark tea. There are no human trials against H. pylori infection.

In stomach cells infected with H. pylori, cinnamaldehyde lowered interleukin-8 release by blocking NF-κB activation ^{13Reference 13Muhammad JS et al. · 2015In vitroAnti-inflammatory effect of cinnamaldehyde in Helicobacter pylori induced gastric inflammation — [in vitro]View study →}.

In mice with adjuvant-induced arthritis, injected trans-cinnamaldehyde reduced paw swelling and arthritis severity. It lowered TNF-α, NF-κB and COX-2, and IL-1β, IL-6, IL-23 and IL-17 ^{14Reference 14El-Tanbouly GS et al. · 2022AnimalNovel anti-arthritic mechanisms of trans-cinnamaldehyde against complete Freund’s adjuvant-induced arthritis in mice — [mouse in vivo]View study →}.

In people, the 2023 umbrella meta-analysis found no significant change in C-reactive protein or malondialdehyde. It did find higher total antioxidant capacity in type 2 diabetes and PCOS, and lower interleukin-6 ^{8Reference 8Sarmadi B et al. · 2023Meta-analysisThe effect of cinnamon consumption on lipid profile, oxidative stress, and inflammation biomarkers in adults: an umbrella meta-analysis of randomized controlled trials — [meta-analysis]View study →}.

A 2020 meta-analysis of 12 trials, using 1.5–4 g of cinnamon powder a day, came out differently: CRP and malondialdehyde fell significantly, interleukin-6 fell marginally and total antioxidant capacity rose ^{29Reference 29Zhu C et al. · 2020Meta-analysisImpact of Cinnamon Supplementation on cardiometabolic Biomarkers of Inflammation and Oxidative Stress: A Systematic Review and Meta-Analysis of Randomized Controlled Trials — meta-analysisView study →}.

Gap: the clearest anti-inflammatory results are in cells and animals, and the pooled human analyses disagree on CRP ^{8,29Reference 8Sarmadi B et al. · 2023Meta-analysisThe effect of cinnamon consumption on lipid profile, oxidative stress, and inflammation biomarkers in adults: an umbrella meta-analysis of randomized controlled trials — [meta-analysis]View study →Reference 29Zhu C et al. · 2020Meta-analysisImpact of Cinnamon Supplementation on cardiometabolic Biomarkers of Inflammation and Oxidative Stress: A Systematic Review and Meta-Analysis of Randomized Controlled Trials — meta-analysisView study →}.

In a 2014 double-blind RCT, 50 people with non-alcoholic fatty liver disease took 1.5 g of cinnamon a day or placebo for 12 weeks. Both groups were given diet and exercise advice ^{16Reference 16Askari F et al. · 2014RCTCinnamon may have therapeutic benefits on lipid profile, liver enzymes, insulin resistance, and high-sensitivity C-reactive protein in nonalcoholic fatty liver disease patients — [randomized controlled trial]View study →}.

The cinnamon group had significant falls in the liver enzymes ALT, AST and GGT, and in fasting glucose, insulin resistance, total cholesterol, triglycerides and hs-CRP ^{16Reference 16Askari F et al. · 2014RCTCinnamon may have therapeutic benefits on lipid profile, liver enzymes, insulin resistance, and high-sensitivity C-reactive protein in nonalcoholic fatty liver disease patients — [randomized controlled trial]View study →}.

The trial authors attributed the effect to improved insulin sensitivity ^{16Reference 16Askari F et al. · 2014RCTCinnamon may have therapeutic benefits on lipid profile, liver enzymes, insulin resistance, and high-sensitivity C-reactive protein in nonalcoholic fatty liver disease patients — [randomized controlled trial]View study →}.

Gap: this is one small trial, the species was not stated, the diet and exercise advice confounds the result, and cassia’s coumarin argues against high doses in anyone with liver disease ^{19,20Reference 19Woehrlin F et al. · 2010Quantification of flavoring constituents in cinnamon: high variation of coumarin in cassia bark from the German retail market and in authentic samples from Indonesia — [comparative study]View study →Reference 20Abraham K et al. · 2010ReviewToxicology and risk assessment of coumarin: focus on human data — [review]View study →}.

A review describes cinnamon polyphenols and cinnamaldehyde inhibiting tau aggregation and the formation of toxic amyloid-β clusters, the two hallmarks of Alzheimer’s disease, in cell and animal models ^{17Reference 17Momtaz S et al. · 2018ReviewCinnamon, a promising prospect towards Alzheimer’s disease — [review]View study →}.

Gap: none of this has been tested in people.

Cinnamaldehyde induces apoptosis (programmed cell death) and cell-cycle arrest in cancer cell lines and inhibits tumour blood-vessel growth, as summarised in mechanistic reviews ^{18Reference 18Peng J et al. · 2024ReviewThe role and mechanism of cinnamaldehyde in cancer — [review]View study →}.

Gap: this work uses the isolated molecule in the laboratory. There is no human evidence that cinnamon prevents or treats cancer.

Coumarin. Coumarin can damage the liver in a susceptible subgroup of people, and the tolerable daily intake is set at 0.1 mg per kg of body weight ^{20Reference 20Abraham K et al. · 2010ReviewToxicology and risk assessment of coumarin: focus on human data — [review]View study →}. Cassia is the main source of coumarin in the diet ^{20Reference 20Abraham K et al. · 2010ReviewToxicology and risk assessment of coumarin: focus on human data — [review]View study →}.

The amount in cassia varies widely, from undetectable to about 10,000 mg/kg in retail sticks, even within one tree ^{19Reference 19Woehrlin F et al. · 2010Quantification of flavoring constituents in cinnamon: high variation of coumarin in cassia bark from the German retail market and in authentic samples from Indonesia — [comparative study]View study →}. Ceylon cinnamon contains only traces ^{21Reference 21Wang Y-H et al. · 2013Cassia cinnamon as a source of coumarin in cinnamon-flavored food and food supplements — [analytical study]View study →}.

Everyday use. Heavy consumers of cassia can reach the tolerable daily intake from food alone, so this matters for regular cooking as well as for supplements ^{20Reference 20Abraham K et al. · 2010ReviewToxicology and risk assessment of coumarin: focus on human data — [review]View study →}. Keep medicinal doses short-term, and avoid them in liver disease.

Liver injury. A 34-year-old woman developed liver injury with jaundice after taking cinnamon for weight loss over a long period, and recovered fully after stopping ^{32Reference 32Yesukumar SJ et al. · 2025Case reportProbable Cinnamon-Induced Mixed Hepatocellular-Cholestatic Liver Injury in a Young Woman: A Case Report — case reportView study →}. A 40-year-old man developed severe liver injury four months after starting two over-the-counter herbal products that both contained cinnamon and fennel; the authors’ review of 13 reported cases of cinnamon-related liver disease found marked abnormalities of clotting time and bilirubin ^{31Reference 31Higaki H et al. · 2018Case reportA Case of Severe Drug-induced Liver Injury Caused by Over the Counter Herb (Cinnamon): Review of Literature — case reportView study →}.

Statins and liver-stressing drugs. A 73-year-old woman on a long-term statin developed hepatitis about a week after starting cinnamon supplements. Both were stopped, and the statin was later restarted alone without problems ^{30Reference 30Brancheau D et al. · 2015Case reportDo cinnamon supplements cause acute hepatitis? — case reportView study →}. Concentrated cassia is best avoided alongside statins and other drugs that can harm the liver ^{30Reference 30Brancheau D et al. · 2015Case reportDo cinnamon supplements cause acute hepatitis? — case reportView study →}.

Diabetes medicines. Several trials show cinnamon lowers blood glucose. Concentrated supplements may add to the effect of diabetes medicines, so blood glucose should be monitored if the two are combined ^{1,3Reference 1Moridpour AH et al. · 2024Meta-analysisThe effect of cinnamon supplementation on glycemic control in patients with type 2 diabetes mellitus: an updated systematic review and dose-response meta-analysis of randomized controlled trials — [meta-analysis]View study →Reference 3Deyno S et al. · 2019Meta-analysisEfficacy and safety of cinnamon in type 2 diabetes mellitus and pre-diabetes patients: a meta-analysis and meta-regression — [meta-analysis]View study →}.

Drug metabolism. In laboratory tests, cinnamaldehyde, the bark’s main compound, progressively inactivates CYP2A6, the enzyme that clears coumarin, nicotine and the breast-cancer drug letrozole. Its effect on CYP1A2, 2B6, 2C9, 2C19, 2D6 and 3A4 needed concentrations at least 15 times higher ^{33Reference 33Chan J et al. · 2016In vitroInactivation of CYP2A6 by the Dietary Phenylpropanoid trans-Cinnamic Aldehyde (Cinnamaldehyde) and Estimation of Interactions with Nicotine and Letrozole — in vitroView study →}. 2-Methoxycinnamaldehyde, another cinnamon compound, acts on CYP2A6 in the same way, and models predict that heavy cinnamon intake could raise nicotine and letrozole levels four- to five-fold ^{34Reference 34Espiritu MJ et al. · 2020In vitroMechanisms of Herb-Drug Interactions Involving Cinnamon and CYP2A6: Focus on Time-Dependent Inhibition by Cinnamaldehyde and 2-Methoxycinnamaldehyde — in vitroView study →}. None of this has been tested in people.

Warfarin. An interaction with warfarin is often mentioned because of cassia’s coumarin. Coumarin itself is not an anticoagulant (that is the related compound dicoumarol), and no controlled study has shown the interaction. Treat it as a precaution.

Digestion and heat. Large medicinal doses may irritate a sensitive gut or aggravate heat conditions.

Essential oil. The concentrated oil irritates mucous membranes and is not taken internally except under professional supervision.

Quality. Cassia is routinely sold simply as “cinnamon”, and many clinical and retail products do not state the species. The two species differ in composition, and cassia carries far more coumarin ^{19,27Reference 19Woehrlin F et al. · 2010Quantification of flavoring constituents in cinnamon: high variation of coumarin in cassia bark from the German retail market and in authentic samples from Indonesia — [comparative study]View study →Reference 27Oketch-Rabah HA et al. · 2018ReviewCinnamon and Cassia Nomenclature Confusion: A Challenge to the Applicability of Clinical Data — reviewView study →}.