Anti-diabetic medications: Cassia cinnamon may reduce blood glucose levels. Suddenly adding cinnamon supplements or large amounts of dietary cinnamon may cause an unexpected drop in blood glucose. When starting cinnamon supplements, monitor blood glucose closely. Anti-diabetic medications include glimepiride, glyburide, insulin, metformin, pioglitazone, rosiglitazone, chlorpropamide, glipizide, and tolbutamide.
Coumarin:Coumarin is a blood thinning drug but is also present in many plants, including cinnamon. Depending on the type of cinnamon and the preparation, coumarin content can vary significantly.1 To avoid inadvertently taking too much coumarin, people taking coumarin should avoid cinnamon supplements and teas.
Drugs that may harm the liver: Large doses of cinnamon may have hepatotoxic effects due to content of coumarin. Large doses of cinnamon should be avoided particularly if one is also taking drugs with potential to harm the liver. Such medications include acetaminophen, amiodarone, carbamazepine, isoniazid, methotrexate, methyldopa, fluconazole, itraconazole, erythromycin, phenytoin, lovastatin, pravastatin, and simvastatin.
Scientific name: Cinnamomum verum, C. aromaticum, C. burmannii, and others
Common name: cinnamon
Cinnamon is commonly used as a spice and flavoring agent.
Cinnamon for supplements and as a spice is obtained from the inner bark of Cinnamomun trees.
Common cinnamon is Cinnamomum verum or C. zylancium.1 Chinese cinnamon is more commonly used in clinical trials and is a related plant C. aromaticum (also called C. cassia Blume).1 Both varieties are sold as cinnamon supplements so it is important to purchase from a trusted company. C. burmannii or Indonesian cassia cinnamon is also sold as a spice and is used for certain aqueous extracts of cinnamon available as supplements.
To avoid potential adverse events, intake of 1 g (1000 mg) cinnamon powder or an equivalent amount of cinnamon extract is recommended. Intake of coumarin from cinnamon extracts is the main concern regarding cinnamon supplements. Most studies have investigated 1 g-3 g of cinnamon powder (typically Cinnamomum aromaticum) without reported adverse events.
Reported adverse events have been due to contact dermatitis, usually to cinnamon oils. People with sensitivity to cinnamon or cinnamon oils should not take cinnamon supplements or extracts. The variable content of coumarin in cinnamon preparations also presents the possibility of consuming too much coumarin with cinnamon supplements. A tolerable daily intake (TDI) for coumarin has been established and is 0.1 mg/kg body weight.3 This level is not likely to be exceeded with intake of 1 g cinnamon per day.
Glycated haemoglobin and blood pressure-lowering effect of cinnamon in multi-ethnic Type 2 diabetic patients in the UK: a randomized, placebo-controlled, double-blind clinical trial.
A prospective, randomized, placebo-controlled, double-blind clinical trial investigated cinnamon supplements for people with type 2 diabetes mellitus (type 2 DM) with glycated hemoglobin (HbA1c) of at least 7%. Fifty-eight people with type 2 DM (age 54.9±9.8 years) treated only with hypoglycemic agents participated in the 12 week trial. Participants were randomly assigned to receive either 2 g powdered Cinnamomum aromaticum (cassia cinnamon) or a starch placebo daily; participants each consumed one capsule with breakfast and one with dinner. Mean HbA1c was significantly decreased after 12 weeks in the cinnamon group (P<0.005; 8.22% to 7.86%) compared with placebo group (8.55% to 8.68%). Systolic and diastolic blood pressured also improved in the cinnamon supplemented group (P<0.001; cinnamon group: SBP: 132.6 to 129.2 mmHg and DBP: 85.2 to 80.2 mmHg; placebo group: SBP: 134.5 to 134.9 mmHg and DBP: 86.8 to 86.1 mmHg). The results of this study suggest that cassia cinnamon supplements may improve HbA1c and blood pressure for people with type 2 DM and elevated glycated hemoglobin levels (>7%). No significant changes in fasting blood glucose were detected when compared to the placebo group. The results of this study are different than in other studies and the efficacy of cassia cinnamon for people with type 2 DM needs further evaluation.4
Effectiveness of cinnamon for lowering hemoglobin A1C in patients with type 2 diabetes: a randomized, controlled trial.
A randomized, placebo-controlled clinical trial investigated the use of cassia cinnamon supplements (powdered Cinnamomum aromaticum) for people with type 2 diabetes mellitus (type 2 DM). One-hundred-nine people with type 2 DM and HbA1c greater than 7% participated in the 90 day study. Participants included children, adolescents, and adults. Participants were randomly assigned to receive either 1 g cassia cinnamon or a placebo daily (consumed before meals). HbA1c was assessed at baseline and after 90 days. After 90 days, HbA1c had decreased by 0.83% (95% CI 0.46-1.20) in the cinnamon group (P<0.001) and by 0.37% (95% CI 0.15-0.59) in the placebo group (not significant, P=0.16). The results of this trial support the idea that cassia cinnamon supplements may help to reduce glycation of hemoglobin (HbA1c). Further studies should be completed to assess these results.5
Effects of a cinnamon extract on plasma glucose, HbA, and serum lipids in diabetes mellitus type 2.
A randomized, placebo-controlled, double-blind clinical trial investigated an aqueous cinnamon extract for type 2 diabetes mellitus (type 2 DM). Sixty-five people with type 2 DM participated in the four month trial. Each capsule contained 115 mg cassia cinnamon extract, corresponding to 1 g cinnamon powder. Participants were randomly assigned to receive either two cinnamon extract capsules or two placebo capsules daily before meals during the trial. A blood sample was collected after an overnight fast at baseline and four months. There was a significantly higher reduction of fasting plasma glucose in the cinnamon group than in the placebo group (10.3% vs. 3.4%). No significant differences were observed for HbA1c or lipid profiles. The results of this study indicate that aqueous cinnamon extracts may help to modify fasting glucose levels for people with type 2 DM. Further studies are needed to clarify these results since some studies have not supported this conclusion.6
Cinnamon improves glucose and lipids of people with type 2 diabetes.
A randomized, double-blind, placebo-controlled clinical trial investigated the efficacy of cinnamon for blood glucose and lipid profile improvement. Sixty people with type 2 diabetes mellitus (type 2 DM) participated in the 60 day trial. Each capsule contained 500 mg of ground cinnamon or wheat flour (placebo). Participants were randomly divided into six groups: 1 g cinnamon (2 capsules), 3 g cinnamon (6 capsules), 6 g cinnamon (12 capsules), 1 g wheat flour (2 capsules), 3 g wheat flour (6 capsules), or 6 g wheat flour (12 capsules). Participants consumed the supplements for 40 days; no cinnamon was given for days 41 to 60. Blood samples were collected at baseline, 20 days, 40 days, and 60 days. Cinnamon supplements reduced the mean fasting serum glucose (18-29%) at all three levels after 40 days. Blood lipids were also improved by cinnamon supplements at all levels after 40 days: triglycerides were reduced by 23-30%, LDL cholesterol was reduced by 7-27%, and total cholesterol was reduced by 12-26%. Changes in HDL cholesterol were not significant and no significant changes were identified for the placebo groups. The results of this study indicate that cinnamon supplements may positively influence blood glucose and lipids for people with type 2 diabetes.7
Antioxidant effects of a cinnamon extract in people with impaired fasting glucose that are overweight or obese.
A double-blind, placebo-controlled, clinical trial investigated the effects of an aqueous extract of Cinnamomum burmanii (Cinnulin PF) on fasting glucose levels in people who are overweight or obese. Twenty-two otherwise healthy adults with fasting glucose between 100 and 125 mg/dL and BMI of 25 to 45 participated in the 12 week trial. Participants were randomly assigned to consume 250 mg aqueous cinnamon extract (Cinnulin PF) or a placebo twice daily. Plasma oxidative stress markers were all significantly improved (p < 0.05) for those consuming cinnamon extract supplements. Ferric Reducing Activity of Plasma (FRAP) and plasma thiol groups both increased in the cinnamon group. Plasma malondialdehyde levels decreased and there was a positive correlation (r = 0.74; p = 0.014) between MDA and plasma glucose in the cinnamon group. These results suggest that aqueous cinnamon extracts could improve oxidative stress and fasting blood glucose for people who are overweight or obese.8
Effects of a water-soluble cinnamon extract on body composition and features of the metabolic syndrome in pre-diabetic men and women.
The effects of cinnamon extract (Cinnulin PF) were studied in a group of men and women with pre-diabetes and metabolic syndrome in a randomized, placebo-controlled, double-blind, clinical trial. Twenty-two men and women (46.0 ± 9.7 years) participated in the twelve week trial. Participants were randomly assigned to receive either cinnamon extract (Cinnulin PF, 500 mg/day) or a placebo daily for the duration of the trial. Changes in fasting blood glucose, systolic blood pressure, and body composition were assessed after twelve weeks; comparisons were made between placebo and cinnamon groups and within each group. Participants in the cinnamon group had significant decreases in fasting blood glucose (-8.4%, p<0.01) and systolic blood pressure (-3.8, p<0.001) compared to baseline. Compared to the placebo group, the cinnamon group also had a significant increase in lean body mass (+1.1%, p<0.002). The results of this small study indicate that this cinnamon extract (Cinnulin PF) affected blood glucose, systolic blood pressure, and lean body mass in beneficial ways for people with metabolic syndrome and pre-diabetes.9
The effect of cinnamon extract on insulin resistance parameters in polycystic ovary syndrome: a pilot study.
A pilot study investigated the effects of cinnamon extract (Cinnulin PF) on insulin resistance in women with polycystic ovary syndrome (PCOS). Participants were randomly assigned to receive 333mg cinnamon extract three times daily or a placebo three times daily for eight weeks. Oral glucose tolerance tests were completed at baseline and after eight weeks of supplementation. In the placebo group, fasting glucose decreased significantly from 92.57 to 85.43 mg/dL (-7.7%, P<0.03). In the cinnamon group, fasting glucose decreased significantly from 95.83 to 79.67 mg/dL (-16.9%, P<0.03). The QUICKI increased significantly in the cinnamon group from 0.35 to 0.38 (7.7%, P<0.03) and HOMA-IR decreased from 2.57 to 1.43 (-44.5%, P<0.03) but remained unchanged in the placebo group, suggesting that cinnamon extract improved insulin sensitivity. At the end of the trial, insulin resistance parameters had to returned to normal levels in the cinnamon extract group (not statistically different from normal controls, P=0.17). Mean glucose levels (AUCglucose/120 minutes) were reduced from 144.88 mg/dL per minute to 114.54 mg/dL per minute (-20.9%, P<0.03) in the cinnamon group. The Matsuda insulin resistance index increased from 4.69 to 10.44 during the treatment period (+122.8%, P<0.05), also consistent with improved insulin sensitivity. These results suggest that cinnamon extract may be beneficial for women with PCOS. Larger trials are necessary to confirm the results of this pilot study.10
Cinnamon has been studied for control of blood glucose and lowering of HbA1c (glycated hemoglobin). Although not all studies are in agreement, the evidence suggests that cinnamon is beneficial for improving blood glucose control. Additional trials are needed to confirm these results.
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