Medically reviewed by Drugs.com. Last updated on Jan 17, 2019.
Scientific Name(s): Cinnamomum cassia Blume, Cinnamomum loureirii Nees, Cinnamomum verum J.S. Presl, Cinnamomum zeylanicum Nees, Cinnamomum burmannii
Common Name(s): Ceylon cinnamon, Chinese cassia, Chinese cinnamon, Cinnamomon, Cinnamon, Saigon cinnamon
Cinnamon is used as a spice and aromatic. Traditionally, the bark or oil has been used to combat microorganisms, diarrhea, and other GI disorders, and dysmenorrhea, although there is limited data to support these uses. Evidence is lacking to support the use of cinnamon in the management of diabetes. Research has focused on anti-inflammatory, antioxidant, and antimicrobial activity.
Ground cinnamon is generally given at dosages of 1 to 3 g/day (range, 120 mg/day to 6 g/day) in studies of diabetes without reported adverse reactions.
Contraindicated in people who are allergic to cinnamon or Peru balsam. Further contraindications have not yet been identified.
Data are insufficient for adequate risk-to-benefit analysis. Cinnamon is generally recognized as safe when used in food.
None well documented. Additive effects may occur if taken with other hepatotoxic drugs.
Heavy exposure may cause skin irritation and allergic reactions.
Information is lacking.
Cinnamon plants have oval-lanceolate, rough-textured leaves approximately 7 to 20 cm in length. The spice is derived from the brown bark, which forms quills with longitudinal striations. Cinnamon bark is available in ground form as a spice. The plant is native to Sri Lanka, southeastern India, Indonesia, South America, and the West Indies.1, 2, 3, 4, 5
Reports of cinnamon use date back to 2000 BC, when texts note the importation of cinnamon from China to Egypt. Cinnamon is also mentioned in the Bible, most often for its aromatic qualities.5 Cinnamon is primarily used as a spice, taste enhancer, or aromatic. Historically, cinnamon has been used to treat GI upset and dysmenorrhea disorders of microcirculation, among other broad-ranging uses.3, 6, 7, 8 The essential oil derived from the plant has been used for its activity against various microorganisms and fungi.3
The primary constituents of the essential oil are 65% to 80% cinnamaldehyde and lesser percentages of other phenols and terpenes, including eugenol, trans-cinnamic acid, hydroxycinnamaldehyde, o-methoxycinnamaldehyde, cinnamyl alcohol and its acetate, limonene, alpha-terpineol, tannins, mucilage, oligomeric procyanidins, and trace amounts of coumarin.3, 4
C. verum differs in composition from C. cassia in eugenol and coumarin content. Coumarin is only found in cassia (0.45%).5 Varying sources of material and extraction techniques alter the chemical composition of the extracts, and may impact the intended medicinal and experimental effects.6, 9
Uses and Pharmacology
The first known clinical trial conducted in humans evaluated pain and healing associated with episiotomies in 144 postpartum women. The trial was randomized, double-blind, and placebo-controlled conducted in Iran and found that 2% (w/w) cinnamon applied to the perineum twice daily for 10 days significantly improved intensity of pain compared with placebo. Also, compared with baseline, reduction of pain intensity was significantly better with cinnamon at the 4- and 8-hour, as well as the 10-day follow up (16%, 26%, 76%, respectively) versus placebo (2%, 4%, 43%), which yielded P values of 0.003, 0.002, and < 0.01, respectively. Wound healing scores were also significantly improved with supplemental cinnamon compared with placebo.59 Pain severity was also significantly reduced with cinnamon supplementation (3 g/day) in young adult women (mean age, 22 years) with primary dysmenorrhea in another double-blind, randomized, placebo-controlled trial (n=80). Although a significant reduction in mean intensity of dysmenorrhea occurred in both the intervention and placebo groups, the benefit of cinnamon (−2.5 points) was significantly greater than that seen with placebo (−0.9 points, P<0.001) overall as well as after the first (P=0.001) and second cycle (P=0.002).73
A few laboratory experiments suggest anti-inflammatory action of certain chemical components in cinnamon. Cinnamaldehyde inhibits nitric oxide production implicated in the inflammatory disease process and also demonstrated inhibition of cyclooxygenase-2 catalyzed prostaglandin E2 biosynthesis.28, 29, 30
Conflicting evidence exists for the action of cinnamon on Helicobacter pylori. In a small clinical study no effect on H. pylori was observed at dosages of extract 80 mg/day, but the study may have been underpowered.5, 31, 32 A laboratory study using H. pylori isolates from hospital patients was able to demonstrate inhibition of all isolates by a methylene chloride cinnamon extract.33 In vitro experimentation was conducted in H. pylori-infected gastric epithelial cells with 24 medicinal plants indigenous to Pakistan to evaluate their effect on secretion of interleukin (IL)-8 and generation of reactive oxygen species (ROS) in order to assess anti-inflammatory and cytoprotective effects. Although no significant direct cytotoxic effects on the gastric cells or bactericidal effects on H. pylori were found, cinnamon extract was observed to have high and strong inhibitory activity on IL-8 at 50 and 100 mcg/mL, respectively, in H. pylori-infected gastric cells. Cinnamon had the strongest effect on IL-8 secretion of all 24 plants tested with effects up to 3.12 mcg/mL and almost complete inhibition at 50 and 100 mcg/mL, comparable to the positive control (curcumin 40 mcM).67
Cinnamon extracts have been shown to exert in vitro activity against some common human pathogens1 as well as fungicidal activity against plant pathogens.34, 35 In vitro inhibition of bacterial endotoxin has been demonstrated by an unidentified component in cinnamon bark.36 The essential oils of cinnamon halted mycelial growth and aflatoxin synthesis in Aspergillus parasiticus at a concentration of only 0.1%.37
Chinese investigators evaluated the combination of cinnamon and pogostemon oils for the treatment of patients with intestinal Candida infections. Patients were randomized to 14-day courses of treatment with 3 capsules, each capsule containing 18 mg cinnamon oil and 9 mg pogostemon oil, or fluconazole 50 mg 3 times daily. All patients treated with cinnamon-pogostemon experienced cure or improvement at the end of treatment.56
Cinnamon extracts appear to exhibit antioxidant action, with an ethanol extract showing more effectiveness than an aqueous extract.23 The relative antioxidant action of cinnamon has been evaluated against other herbs and spices, and against alpha-tocopherol.5, 23, 24, 25, 26
In an experiment in which rats with induced diabetes were fed cinnamon via drinking water, no effect on blood glucose levels was shown. The researchers noted a significant decrease in platelet counts and a slight increase in hemoglobin in the rats.10
Data from several meta-analyses,20, 55, 57, 71, 72 systematic reviews,21, 22, 70 and clinical trials13, 14, 17, 18, 19, 51, 52, 53, 54, 69 conducted in patients with metabolic syndrome, prediabetes, and diabetes mellitus (type 1 and type 2) report equivocal results regarding the ability of cinnamon supplementation to improve glucose metabolism and related parameters. Statistically significant results were often not clinically relevant. Overall, evidence is lacking to support the clinical use of cinnamon in the management of diabetes. Variables suggested to account for the differences in trial outcomes include differing concurrent therapies, degree of control of the condition, and differences of populations studied.18, 20, 64
A systematic review of randomized, controlled trials that evaluated the effect of cinnamon supplementation (Cinnamomum spp) on various fractions of blood lipids identified 13 trials (N=750) that met inclusion criteria. Studies were conducted in 10 countries, mostly in patients with diabetes, and published between 2003 and 2015; only 2 explicitly excluded patients on lipid-lowering medications. Meta-analyses found a significant improvement with cinnamon compared to controls on total cholesterol and triglycerides (weighted mean differences, −13.92 mg/dL and −23.91 mg/dL, respectively; P<0.01 each) but no significant effect was found for low-density lipoprotein or high-density lipoprotein cholesterol. Doses of cinnamon (any species or standardized extract) ranged from 1 to 6 g/day and were given for 2 to 4 months. A positive correlation was found with duration of supplementation but not dose.70
Single bolus doses of cinnamon in healthy volunteers led to increased insulin sensitivity15 and decreased postprandial blood glucose levels16, 62 in 3 small studies. Similarly, a single-dose of 100 mL of cinnamon tea (6 g per 100 mL of Cinnamomum burmannii) was found to slightly decrease postprandial blood glucose levels and significantly lower postprandial maximum glucose in nondiabetic adults.66
A randomized clinical trial studying various dosages of cassia cinnamon powder (1, 3, or 6 g/day) over 40 days found a statistically and clinically significant improvement in blood glucose control among patients with type 2 diabetes. A reduction in cardiovascular risk factor biomarkers was also observed.13 A second trial also found a significant reduction in fasting glucose levels at 3 g/day over 4 months, but no significant difference in the lipid profile.14 Daily doses of 1 g added to usual care produced a significant reduction in hemoglobin A1c (HbA1c) compared with usual care in a 3-month study.51 Significant improvements in HbA1c, fasting blood glucose, and systolic and diastolic blood pressure were seen in a study of 2 g/day compared with placebo in a 12-week study in type 2 diabetes mellitus.52 Another small study looked at the effects of 1.2 g of cinnamon per day, and did not find a significant reduction in systolic blood pressure, and HbA1c actually increased.53 A randomized, controlled trial evaluated cinnamon extract at daily doses of 120 and 360 mg in type 2 diabetes mellitus patients managed solely with gliclazide (a sulfonylurea) during the 3-month study. Both doses of cinnamon extract produced significant reductions in HbA1c, and the lower dose significantly reduced serum triglycerides.54
However, other clinical trials have been unable to replicate these positive findings in patients with type 1 or 2 diabetes at dosages of cinnamon 1 to 1.5 g/day.17, 18, 19 A meta-analysis of 5 trials20 and systematic reviews21, 22 have found no significant effect on glycated hemoglobin (A1C), fasting blood glucose, or lipid profiles. A Cochrane review pooled data from 10 studies (n = 577), including data from several of the studies mentioned above. This review concluded that cinnamon was no more effective than placebo, other treatments, or no treatment for reduction of blood glucose and HbA1c.55
A meta-analysis of 3 placebo-controlled, randomized clinical trials evaluating short-term use of cinnamon on blood pressure in prediabetic or type 2 diabetic patients identified a significant benefit with cinnamon administration. Cinnamon powder or extract (500 mg to 2.4 g/day) was administered for 12 weeks. Significant changes in blood pressure appeared to be more closely associated with patients’ baseline blood pressure rather than dose of cinnamon, such that patients with a higher baseline pressure benefited from a lower dose than patients with a lower baseline pressure.57 Similarly, blood pressure as well as several metabolic parameters (ie, body mass index [BMI], waist circumference, waist:hip ratio, percent body fat) were improved significantly with cinnamon compared to controls in treatment-naïve Asian Indians with newly diagnosed metabolic syndrome. Cinnamon was dosed at 3 g/day for 16 weeks in a randomized, double-blind, placebo-controlled design.69
Postprandial working memory was not found to be significantly different after a single dose of 2 g of cinnamon in a small double-blind trial that randomized 48 elderly prediabetes patients (median age, 71 to 75 years) to receive a single dose of turmeric (1 g), cinnamon (2 g), both (1 and 2 g, respectively), or placebo prior to a white-bread breakfast. Of a total score of 3, postprandial working memory increased over the 6-hour observation period from 2.6 to 2.9 (P = 0.05) with turmeric users compared with non-turmeric users. These changes were not noted with cinnamon users and were independent of body fat, glycemia, insulin, or Alzheimer disease biomarkers.63
The revised American Diabetes Association (ADA) standards of medical care in diabetes statement (2015) states that evidence is insufficient to support use of cinnamon to improve glycemic control in diabetic patients (expert opinion).64
A randomized, double-blind, placebo-controlled trial (N = 45) investigated the insulin sensitizer effects of cinnamon supplementation in patients with nonalcoholic fatty liver disease (NAFLD), the most prevalent etiology of hepatic injury. NAFLD characteristics were significantly improved by the supplementation of 1,500 mg/day of cinnamon for 12 weeks compared with placebo; insulin resistance, insulin sensitivity, fasting blood sugar, total cholesterol, triglycerides, liver enzymes, and the inflammatory marker (C-reactive protein) were all significantly improved with cinnamon (P < 0.001 to P = 0.029).60
In an experiment to determine the wound healing action of an ethanol extract of cinnamon, researchers suggested the significant increase in wound healing was attributable to antioxidant activity.27
The first known clinical trial conducted in humans evaluated pain and healing associated with episiotomies in 144 postpartum women. The trial was randomized, double-blind, and placebo-controlled conducted in Iran and found that 2% (w/w) cinnamon applied to the perineum twice daily for 10 days significantly improved redness, edema, ecchymosis, discharge approximation wound healing scores from baseline (53%) compared with placebo (6%). Additionally, the overall healing scores were significantly lower in the cinnamon group versus placebo (P < 0.01). Compared with baseline, significantly more women experienced bloody or purulent discharges (4) in the placebo group than the cinnamon group (0) (P = 0.025). Pain intensity and reduction in pain were also significantly better with supplemental cinnamon.59
Angiogenesis inhibition, antiproliferative, and immunomodulatory effects have been demonstrated leading some researchers to suggest value in screening cinnamon for anticancer effects.38, 39, 40 A stimulatory effect on human osteoblast cells has been demonstrated as well as some estrogenic activity.41 A dose-dependent neuroprotective effect was demonstrated in rats with glutamate-induced neuronal cell death.7
A small randomized, placebo-controlled, double-blind trial found supplementation with cinnamon 1,500 mg/day (4 capsules 3 times daily) for 6 months significantly improved menstrual cyclicity from baseline (P = 0.0076) in women with polycystic ovary syndrome, whereas no improvements were seen in the placebo group. No serious adverse events were reported.61 In addition to this study, a 2017 systematic review and meta-analysis of nutritional supplements and herbal medicines for polycystic ovary syndrome identified a second randomized controlled trial that investigated Cinnamomum sp in this patient population. Women received 1,000 mg daily for 8 weeks or placebo. Primary data, however, were apparently not reported in this 2nd study so the between groups' outcomes could not be examined. Incongruencies throughout this systematic review between the reference numbers in the table of studies vs reference numbers in the text led to conflicting data for many of the meta-analyses and/or interventions summarized.68
Ground cinnamon typically has been given at dosages of 1 to 3 g/day (range, 120 mg/day to 6 g/day) in studies of diabetes, pre-diabetes, and metabolic syndrome13, 17, 18, 19, 69 and 80 mg/day in an ethanol extract in a study of activity against Helicobacter, without reported adverse reactions.30
Pregnancy / Lactation
Data are insufficient for adequate risk-benefit analysis. Cinnamon is generally recognized as safe when used as food. Avoid dosages above those found in food because safety and efficacy are not proven.42
Cinnamon may interact with other hepatically metabolized medications; a case of acute hepatitis was reported in a 73-year-old female with multiple co-morbid conditions following 1 week of cinnamon supplementation while on a polypharmacy regimen that included rosuvastatin 40 mg/day.65
Cinnamon has been given Generally Recognized As Safe (GRAS) status by the FDA.5 At dosages of up to 6 g/day, no significant adverse reactions have been reported.13, 17, 18, 19 Human consumption of large quantities of cinnamon bark or moderate quantities of cinnamon oil has been shown to increase heart rate, intestinal motility, respiratory rate, and perspiration via a chemical stimulation of the vasomotor center. This state of accelerated body function is followed by a period of centralized sedation that includes sleepiness or depression.3
Contact dermatitis has been reported after single exposure and repeated use of cinnamon-containing preparations.43, 44, 45 An acute exacerbation of rosacea has been reported consequent to consumption of cinnamon oil pills.21
Oral mucosal lesions have been reported, commonly associated with cinnamon-flavored chewing gum and candies5, 46, 47 and exposure to cinnamon oil has been cited as a risk factor for oral cancers.48, 49, 50
A case of acute hepatitis with cholestatic feature was reported in a 73-year-old female within 1 week of her taking cinnamon supplementation while on a high-dose regimen of rosuvastatin (40 mg/day). The patient had a significant medical history including polypharmacy with several hepatically metabolized medications, alcohol and tobacco use, and multiple co-morbid diagnoses that included CAD, diabetes, hyperlipidemia, cholestectomy, and recurrent abdominal pain. The elevated liver enzymes and abdominal pain present upon admission slowly improved after discontinuing rosuvastatin and cinnamon, and did not recur with reintroduction of rosuvastatin. Because coumarin in cinnamon has been associated with acute liver damage, combined with the recent timing of new onset symptoms related to recent cinnamon supplementation, the authors suspected the higher dose of rosuvastatin plus cinnamon led to medication-induced acute hepatitis.65
Information is lacking. Teratogenicity in chick embryos has been reported in one study; in another, no evidence of teratogenicity in rats given a methanol extract of cinnamon was demonstrated.1 A case report describes vomiting, diarrhea, and loss of consciousness in a child who consumed 60 mL of cinnamon oil.5
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