Talaei B, Amouzegar A, Sahranavard S, Hedayati M, Mirmiran P, Azizi F. Effects of cinnamon consumption on glycemic indicators, advanced glycation end products, and antioxidant status in type 2 diabetic patients. Nutrients. September 8, 2017;9(9):991. doi: 10.3390/nu9090991.

Managing diabetes mellitus is essential to prevent complications and improve health in those with the disease. Controlling the disease can involve dietary changes, exercise, and/or medications. Recent studies report protective effects of some herbal products in treating type 2 diabetes. Oxidative stress and advanced glycation end products (AGEs) are implicated in the progression of diabetes, but few studies have examined the effects of botanicals on AGEs. Cinnamon (Cinnamomum verum syn. C. zeylanicum, Lauraceae) contains antioxidant compounds and is used in traditional medicine to treat chronic diseases including cardiovascular disease and diabetes. These authors conducted a double-blind, randomized, placebo-controlled clinical trial to investigate the effects of cinnamon supplementation on glycemic indices, AGEs, and antioxidant status in patients with type 2 diabetes.

The trial, conducted at the Endocrinology and Metabolism Center at Shahid Beheshti University of Medical Sciences in Tehran, Iran, between 2016 and 2017, specifically examined the effects of 3 grams of cinnamon supplementation daily on fasting plasma glucose (FPG), glycated hemoglobin (HbA1c), homeostasis model assessment for insulin resistance (HOMA-IR), the AGE carboxymethyl lysine, total antioxidant capacity, and the oxidative stress biomarker malondialdehyde (MDA) in patients with type 2 diabetes. Included patients had a history of diabetes of less than 8 years, body mass index (BMI) of 18.5-30 kg/m², FPG <180 mg/dL, and 2-hour blood glucose <250 mg/dL with metformin therapy. Exclusion criteria were certain other chronic diseases, pregnancy or lactation, insulin use or changes in medical management of diabetes during the study, use of alcohol or anti-inflammatory medications, drug abuse, allergy to cinnamon, and the development of side effects.

The patients were randomly assigned to either the cinnamon (n=22) or placebo (n=22) group. The study capsules, which were identical in the 2 groups, contained 1000 mg of powdered cinnamon or microcrystalline cellulose (placebo). At baseline and at week 4, the patients were given a 4-week supply of capsules and instructed to consume 1 capsule 3 times daily after each main meal, and to continue their usual physical activity, dietary habits, and metformin therapy. The patients were contacted weekly to encourage compliance to the study, and leftover capsules were counted at 4 and 8 weeks. At baseline, each patient's sociodemographic information was recorded, their weight and height were measured, and BMI was calculated. Fasting blood draws to measure glycemic indices and inflammatory factors were conducted at baseline and after week 8.

A total of 44 patients (mean age, 57.61 ± 8.70 years) were recruited. No significant between-group differences were observed in lifestyle or anthropometric characteristics or in glycemic indices or inflammatory factors at baseline. Of the 22 patients assigned to the placebo group, 3 patients withdrew from the study. In the cinnamon group, 2 patients withdrew. Reasons for withdrawal included travel and lack of cooperation. Final analysis included 19 patients in the placebo group and 20 in the cinnamon group.

After 8 weeks of intervention, the authors observed no significant differences between the groups or in each group compared with baseline values for any of the glycemic indices or inflammatory factors. There was a trend toward declining mean FPG in the cinnamon group, versus a slight increase in the placebo group, but within-group variation was large and the between-group difference was not quite significant (−11.65 ± 29.34 mg/dL vs. 8.57 ± 35.10 mg/dL; P=0.06).

The findings of this study agree with earlier studies in patients with diabetes showing no significant change in FPG, HbA1c, or insulin levels after 1 g of cinnamon intake daily for 3 months¹ and showing no improvement in FPG, oral glucose tolerance, or insulin sensitivity with 1.5 g of cinnamon daily for 6 weeks.² However, the authors suggest that nonsignificant changes in glycemic markers in those studies might have become statistically significant given a longer study period. Another cited study, with a treatment period of 90 days, reported improved HbA1c levels with 1 g of cinnamon supplementation daily.³ Other findings on the effects of cinnamon intake on inflammatory indicators and antioxidant factors are conflicting and limited, say the authors. Limitations of this study include its short duration, small size, and lower dose of cinnamon compared to that used in some animal studies. Further, no information was given on the source or chemical composition of the cinnamon product. Variation in the quality of test substances could contribute to inconsistent study results.

The study was funded by a grant from the Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences.

―Shari Henson

References

¹Blevins SM, Leyva MJ, Brown J, Wright J, Scofield RH, Aston CE. Effect of cinnamon on glucose and lipid levels in non-insulin-dependent type 2 diabetes. Diabetes Care. 2007;30(9):2236-2237.

²Vanschoonbeek K, Thomassen BJ, Senden JM, Wodzig WK, van Loon LJ. Cinnamon supplementation does not improve glycemic control in postmenopausal type 2 diabetes patients. J Nutr. 2006;136(4):977-980.