An Updated Systematic Review and Meta-Analysis

Ann Fam Med 2013 Sep 01;11(5)452-459, RW Allen, E Schwartzman, WL Baker, CI Coleman, OJ Phung

TAKE-HOME MESSAGE

• What is the glycemic-lowering effect of cinnamon?
• A meta-analysis of 10 randomized controlled trials (543 patients) evaluated cinnamon’s effect on glycemia and lipid levels.
• Cinnamon lowers the levels of fasting plasma glucose, total cholesterol, LDL-C, and triglyceride levels and increases HDL-C; however, it has no effect on hemoglobin A1C.

The glucose-lowering effects of cinnamon were found by mistake when a study using apple pie to increase blood sugar found that it did not raise glucose as much as other sugary foods. Cinnamon in the pie was found to be the stabilizing factor.

The ideal dose is yet to be determined, but 1 to 3 gm/day appears to be a good start according to available data. You don’t have to use a special product. Most cinnamon available in grocery stores is a combination of Cinnamomum aromaticum and C. verum; both forms were included in this meta-analysis. One tsp = 4.5 gm; so shooting for ½ tsp, or about 2 gm, daily is reasonable. The effects do not appear to increase with escalating doses.

To put the glucose-lowering effects of cinnamon in perspective, the authors state that it is about half as potent as metformin and more potent than sitagliptin, which costs ~$220 for 30-day supply of 50-mg tablets. A 2.5-oz bottle of cinnamon contains 15 tsp, for about $4/bottle. Using a half tsp (2 gm/day) is about $4 for a 30-day supply. But remember: cinnamon does not appear to have a significant effect on hemoglobin A1C.

If you choose to recommend cinnamon, encourage your patients to sprinkle ½ tsp over their oatmeal and fresh fruit each morning. If they want to further reduce the glycemic index of the meal, suggest that they add a teaspoon of fiber-rich ground flax or chia seeds. Or, suggest a sprinkle of cinnamon as a topper in the morning java or tea. Let food be thy medicine!

ABSTRACT

Purpose: Cinnamon has been studied in randomized controlled trials (RCTs) for its glycemic-lowering effects, but studies have been small and show conflicting results. A prior meta-analysis did not show significant results, but several RCTs have been published since then. We conducted an updated systematic review and meta-analysis of RCTs evaluating cinnamon’s effect on glycemia and lipid levels.

Methods: MEDLINE, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) were searched through February 2012. Included RCTs evaluated cinnamon compared with control in patients with type 2 diabetes and reported at least one of the following: glycated hemoglobin (A1c), fasting plasma glucose, total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), or triglycerides. Weighted mean differences (with 95% confidence intervals) for endpoints were calculated using random-effects models.

Results: In a meta-analysis of 10 RCTs (n = 543 patients), cinnamon doses of 120 mg/d to 6 g/d for 4 to 18 weeks reduced levels of fasting plasma glucose (−24.59 mg/dL; 95% CI, −40.52 to −8.67 mg/dL), total cholesterol (−15.60 mg/dL; 95% CI, −29.76 to −1.44 mg/dL), LDL-C (−9.42 mg/dL; 95% CI, −17.21 to −1.63 mg/dL), and triglycerides (−29.59 mg/dL; 95% CI, −48.27 to −10.91 mg/dL). Cinnamon also increased levels of HDL-C (1.66 mg/dL; 95% CI, 1.09 to 2.24 mg/dL). No significant effect on hemoglobin A1c levels (−0.16%; 95%, CI −0.39% to 0.02%) was seen. High degrees of heterogeneity were present for all analyses except HDL-C (I2 ranging from 66.5% to 94.72%).

Conclusions: The consumption of cinnamon is associated with a statistically significant decrease in levels of fasting plasma glucose, total cholesterol, LDL-C, and triglyceride levels, and an increase in HDL-C levels; however, no significant effect on hemoglobin A1c was found. The high degree of heterogeneity may limit the ability to apply these results to patient care, because the preferred dose and duration of therapy are unclear.

Practice Update:  http://www.practiceupdate.com/journalscan/6098