Benefits
Fasting Blood Sugar in Pooled Randomized Trials
Meta-analyses of randomized trials in adults with type 2 diabetes found that cinnamon lowered fasting blood sugar compared with control. One pooled 10 trials and found a drop of about 25 mg/dL; a larger one of 24 trials also found lower HbA1c. Results varied widely between trials, and doses ranged from 120 mg to 6 g a day.
Blood Sugar Response After a Meal
In 14 healthy adults, adding 6 g of cinnamon to a rice pudding lowered the rise in blood sugar after the meal and slowed stomach emptying. In 10 adults with impaired glucose tolerance, 6 g of Ceylon cinnamon taken with a glucose drink did not change blood sugar or insulin. The two studies used different cinnamon and test meals.
Insulin Sensitivity and Insulin Levels
A cinnamon compound acted like insulin in fat cells in the lab. In people, a 12-week trial of 12 g of cassia a day in adults with impaired glucose tolerance found no change in insulin sensitivity measured by clamp. A pooled analysis of 24 trials found lower HOMA-IR, an insulin resistance score, but no significant change in insulin levels.
Triglycerides and Total Cholesterol
A meta-analysis of 13 randomized trials with 750 people found that cinnamon lowered triglycerides by about 24 mg/dL and total cholesterol by about 14 mg/dL, with no significant change in LDL or HDL. Longer use was linked to larger changes; the dose was not. A pooled analysis limited to type 2 diabetes also found lower LDL.
C-Reactive Protein, a Marker of Inflammation
A pooled analysis of 6 randomized trials with 285 people found that cinnamon lowered blood C-reactive protein (CRP) by about 0.8 mg/L. Results differed between trials, and the drop was larger when CRP started above 3 and when trials lasted longer than 12 weeks.
Antioxidant Markers With a Water Extract
In a placebo-controlled trial in 22 overweight or obese adults with impaired fasting glucose, those taking 250 mg of a water extract of cinnamon twice a day for 12 weeks had higher blood antioxidant power and thiol groups and lower malondialdehyde, a marker of lipid oxidation. Effects were larger at 12 weeks than at 6.
Mechanism of action
Slower Stomach Emptying After a Meal
Measured by ultrasound in healthy adults, adding 6 g of cinnamon to a rice pudding slowed how fast the stomach emptied. The authors say slower emptying partly explains the smaller rise in blood sugar after that meal, although the glucose change was larger than the change in emptying.
Insulin-Like Signaling in Fat Cells (Lab Study)
In cultured fat cells, a methylhydroxychalcone polymer (MHCP) from cinnamon raised glucose uptake and glycogen production about as much as insulin did, switched on the insulin receptor and worked through PI3-kinase. This is a cell study; it has not been shown to happen this way in people.
Antioxidant Activity of Water-Soluble Compounds
A water extract of cinnamon raised blood antioxidant power and lowered a lipid oxidation marker over 12 weeks in adults with impaired fasting glucose. Malondialdehyde levels correlated with blood glucose in that trial.
Coumarin Content of Cassia
Cassia bark can contain large amounts of coumarin, up to about 10,000 mg/kg in retail sticks, with wide variation even within a single tree, while Ceylon contains only traces. EFSA set a tolerable daily intake of 0.1 mg/kg body weight because coumarin can harm the liver, and heavy cassia users may reach it.
Clinical trials
Systematic review and meta-analysis of randomized controlled trials comparing cinnamon with control, using weighted mean differences (Allen et al. 2013, Ann Fam Med)
10 trials with 543 adults with type 2 diabetes; cinnamon powder or water extract at 120 mg to 6 g a day for 4 to 18 weeks.
Fasting plasma glucose fell by 24.59 mg/dL, total cholesterol by 15.60 mg/dL, LDL by 9.42 mg/dL and triglycerides by 29.59 mg/dL, and HDL rose by 1.66 mg/dL. HbA1c did not change significantly (minus 0.16 percent, confidence interval crossing zero). Heterogeneity was high for every outcome except HDL, and the authors say the best dose and duration are unclear.
Updated systematic review and dose-response meta-analysis of randomized controlled trials, using standardized mean differences (Moridpour et al. 2024, Phytother Res)
24 trials in adults with type 2 diabetes.
Cinnamon lowered fasting blood sugar (SMD -1.32, p < 0.001), HOMA-IR (SMD -1.32, p < 0.001) and HbA1c (SMD -0.67, p = 0.011) compared with control. Serum insulin did not change significantly (SMD -0.17, p = 0.058). Results are reported as standardized mean differences, so they cannot be read as mg/dL or percentage point changes.
Randomized placebo-controlled trial with six groups, three cinnamon doses and three matching placebos, for 40 days followed by a 20-day washout (Khan et al. 2003, Diabetes Care)
60 adults with type 2 diabetes (30 men, 30 women), average age 52.
All three doses lowered fasting serum glucose (18 to 29 percent), triglycerides, LDL and total cholesterol, and HDL did not change; the placebo groups did not change. In 2025 the journal issued an expression of concern after an independent statistical review found baseline differences between groups, unclear randomization and blinding, possible misreporting of standard deviations and no loss to follow-up, so these results should be read with caution.
Crossover trial measuring gastric emptying by real-time ultrasound and blood glucose after 300 g rice pudding with or without 6 g cinnamon (Hlebowicz et al. 2007, Am J Clin Nutr)
14 healthy adults with normal fasting blood glucose.
Cinnamon lowered the blood glucose response after the meal and slowed gastric emptying (P < 0.05 for both). The drop in glucose was more pronounced than the slowing of emptying. Satiety did not change.
Crossover trial of 6 g Ceylon cinnamon (C. zeylanicum) capsules or placebo taken with a standard 75 g oral glucose tolerance test, sampled for 180 minutes (Wickenberg et al. 2012, Br J Nutr)
10 adults with impaired glucose tolerance.
Ceylon cinnamon had no significant effect on blood glucose, insulin response, glycemic index or insulinemic index. The authors note that switching from cassia to Ceylon to avoid coumarin may lose the glucose effects reported with cassia.
Randomized double-blind placebo-controlled trial of capsules equal to 6 g cassia cinnamon twice a day for 12 weeks, with insulin sensitivity measured by euglycemic hyperinsulinemic clamp (Wickenberg et al. 2014, Nutr J)
21 adults with impaired glucose tolerance; 17 completed (9 cinnamon, 8 placebo).
Cassia cinnamon had no significant effect on insulin sensitivity, HbA1c, fasting glucose or BMI, and no significant changes were seen in blood lipids or liver enzymes. The trial was small.
Double-blind placebo-controlled trial of 250 mg water extract of cinnamon (Cinnulin PF) or placebo twice a day for 12 weeks (Roussel et al. 2009, J Am Coll Nutr)
22 overweight or obese adults (BMI 25 to 45) with impaired fasting glucose.
The extract raised plasma antioxidant power (FRAP) and thiol groups and lowered plasma malondialdehyde, with larger effects at 12 weeks than at 6. Malondialdehyde correlated with plasma glucose (r = 0.74, p = 0.014).
Systematic review and meta-analysis of randomized controlled trials using weighted mean differences (Vallianou et al. 2019, Complement Ther Med)
6 trials with 285 participants.
Cinnamon lowered serum CRP by 0.81 mg/L (p = 0.004), with significant heterogeneity between trials. Reductions were larger when baseline CRP was above 3 and in trials longer than 12 weeks. The authors call for better designed studies to confirm the finding.
Systematic review and meta-analysis of randomized controlled trials using weighted mean differences, with meta-regression on dose and duration (Maierean et al. 2017, J Clin Lipidol)
13 trials with 750 participants.
Cinnamon lowered triglycerides by 23.91 mg/dL and total cholesterol by 13.92 mg/dL (P < .01 for both). LDL (P = .10) and HDL (P = .21) did not change significantly. Changes were linked to how long cinnamon was taken, not to the dose.