Type 2 diabetes is a chronic disease that is increasing in prevalence despite the growing options for management. Cinnamon is a spice that may have a role in lowering blood glucose values through its insulin-like actions.1,2 Previous studies have shown that cinnamon extracts and cinnamon polyphenols can increase insulin receptor beta proteins and GLUT4 proteins in vitro and in vivo in animal studies. Insulin beta proteins are substrates that activate insulin receptors, whereas GLUT4 proteins serve as insulin-regulated transporters to transport glucose into the cell. Decreased GLUT4 proteins have been associated with insulin resistance as seen in Type 2 diabetes. These pharmacological mechanisms of cinnamon may lead to lower blood glucose levels in diabetic patients and studies have shown conflicting results.1
In a 12-week double-blind randomized clinical trial by Akilen and colleagues, the effects of cinnamon were studied in 58 subjects with Type 2 diabetes. The subjects were randomly assigned to receive either cinnamon-filled (Cinnamomum cassia) capsules (2 gm/d given three times daily) or placebo. Cinnamon was well tolerated by the subjects in this study. The results showed that there were significant changes in HbA1c (decrease of 0.36%±0.90% with cinnamon compared to an increase of 0.12%±0.82% with placebo, p=0.002), systolic blood pressure (decrease of 4.00±1.77 with cinnamon compared to increase of 1.00±3.95 with placebo, p=0<0.001), and diastolic blood pressure (decrease of 4.00±4.25mmHg with cinnamon compared to 1.00±4.32mmHG with placebo, p<0.001). Subjects with higher baseline HbA1c levels showed greater reductions in HbA1c post-intervention (p=0.008). The reductions in fasting blood glucose, lipid levels, weight, BMI, and waist circumference were not statistically significant between the placebo and cinnamon groups post-intervention. It is important to note that all subjects received diet and lifestyle counseling from dieticians two or more times weekly throughout the study, and the subjects were taking sulfonylurea and metformin.1
Another 8-week, double-blind, randomized clinical trial by Hasanzade and colleagues evaluated the effect of cinnamon on blood glucose levels in 70 Iranian subjects with Type 2 diabetes. The subjects were assigned to receive either cinnamon (Cinnamomum cassia) or placebo. The cinnamon group received 1 gm of cinnamon by mouth twice daily for the first 30 days, then 1 gm per day for the next 30 days. Fasting blood glucose levels were assessed on day 30 and then on day 60 of the study. The study found no significant reductions in fasting blood glucose or HbA1c levels between the cinnamon and placebo groups. The results of this study might not reflect the true effect of cinnamon on blood glucose levels since the duration of the study might be too short to detect a significant change in HbA1c level, and a lower daily dose was used compared to the Akilen study. In addition, there was no protocol to ensure the purity of the cinnamon capsules in this trial. Compliance was assessed based on self-reports from the subjects and pill counts at the end of the day 30 and day 60 of the study. The study also did not evaluate the safety profile of cinnamon.2
The use of Cinnamomum cassia (cinnamon) has been demonstrated to be safe for up to 4 months in clinical trials. However, long-term use at high doses may lead to liver toxicity as some products of Cinnamomum cassia may contain coumarin, which has been associated with hepatotoxicity in animals and in high doses in humans.3 With conflicting results, the efficacy of Cinnamomum cassia ...