Qin, B., K. S. Panickar and R. A. Anderson. 2010. Cinnamon: potential role in the prevention of insulin resistance, metabolic syndrome, and type 2 diabetes. J Diabetes Sci Technol. 4, 3: 685-693.

Abstract: Metabolic syndrome is associated with insulin resistance, elevated glucose and lipids, inflammation, decreased antioxidant activity, increased weight gain, and increased glycation of proteins. Cinnamon has been shown to improve all of these variables in in vitro, animal, and/or human studies. In addition, cinnamon has been shown to alleviate factors associated with Alzheimer's disease by blocking and reversing tau formation in vitro and in ischemic stroke by blocking cell swelling. In vitro studies also show that components of cinnamon control angiogenesis associated with the proliferation of cancer cells. Human studies involving control subjects and subjects with metabolic syndrome, type 2 diabetes mellitus, and polycystic ovary syndrome all show beneficial effects of whole cinnamon and/or aqueous extracts of cinnamon on glucose, insulin, insulin sensitivity, lipids, antioxidant status, blood pressure, lean body mass, and gastric emptying. However, not all studies have shown positive effects of cinnamon, and type and amount of cinnamon, as well as the type of subjects and drugs subjects are taking, are likely to affect the response to cinnamon. In summary, components of cinnamon may be important in the alleviation and prevention of the signs and symptoms of metabolic syndrome, type 2 diabetes, and cardiovascular and related diseases.

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Gruenwald, J., J. Freder and N. Armbruester. 2010. Cinnamon and health. Crit Rev Food Sci Nutr. 50, 9: 822-834.

Abstract: Cinnamon has been used as a spice and as traditional herbal medicine for centuries. The available in vitro and animal in vivo evidence suggests that cinnamon has anti-inflammatory, antimicrobial, antioxidant, antitumor, cardiovascular, cholesterol-lowering, and immunomodulatory effects. In vitro studies have demonstrated that cinnamon may act as an insulin mimetic, to potentiate insulin activity or to stimulate cellular glucose metabolism. Furthermore, animal studies have demonstrated strong hypoglycemic properties. However, there are only very few well-controlled clinical studies, a fact that limits the conclusions that can be made about the potential health benefits of cinnamon for free-living humans. The use of cinnamon as an adjunct to the treatment of type 2 diabetes mellitus is the most promising area, but further research is needed before definitive recommendations can be made.

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Ponnusamy, S., R. Ravindran, S. Zinjarde, S. Bhargava and A. R. Kumar. 2010. Evaluation of Traditional Indian Antidiabetic Medicinal Plants for Human Pancreatic Amylase Inhibitory Effect In Vitro.Evid Based Complement Alternat Med. 2011; 2011. pii: 515647.

Abstract: Pancreatic α-amylase inhibitors offer an effective strategy to lower the levels of post prandial hyperglycemia via control of starch breakdown. Eleven Ayurvedic Indian medicinal plants with known hypoglycemic properties were subjected to sequential solvent extraction and tested for α-amylase inhibition, in order to assess and evaluate their inhibitory potential on pancreatic α-amylase. Analysis of 91 extracts, showed that 10 exhibited strong Human Pancreatic Amylase (HPA) inhibitory potential. Of these, 6 extracts showed concentration dependent inhibition with IC₅₀ values, namely, cold and hot water extracts from Ficus bengalensis bark (4.4 and 125 μgmL⁻¹), Syzygium cumini seeds (42.1 and 4.1 μgmL⁻¹), isopropanol extracts of Cinnamomum verum leaves (1.0 μgmL⁻¹) and Curcuma longa rhizome (0.16 μgmL⁻¹). The other 4 extracts exhibited concentration independent inhibition, namely, methanol extract of Bixa orellana leaves (49μgmL⁻¹), isopropanol extract from Murraya koenigii leaves (127 μgmL⁻¹), acetone extracts from C. longarhizome (7.4 μgmL⁻¹) and Tribulus terrestris seeds (511 μgmL⁻¹). Thus, the probable mechanism of action of the above fractions is due to their inhibitory action on HPA, thereby reducing the rate of starch hydrolysis leading to lowered glucose levels. Phytochemical analysis revealed the presence of alkaloids, proteins, tannins, cardiac glycosides, flavonoids, saponins and steroids as probable inhibitory compounds.

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Hlebowicz, J., G. Darwiche, O. Björgell and L.-O. Almér. 2009. Effect of cinnamon on postprandial blood glucose, gastric emptying,and satiety in healthy subjects. The American Journal of Chemical  Nutrition. 85: 1552-1556. 

ABSTRACT

Background: Previous studies of patients with type 2 diabetes showed that cinnamon lowers fasting serum glucose, triacylglycerol, and LDL- and total cholesterol concentrations.

Objective: We aimed to study the effect of cinnamon on the rate of gastric emptying, the postprandial blood glucose response, and satiety in healthy subjects.

Design: The gastric emptying rate (GER) was measured by using standardized real-time ultrasonography. Fourteen healthy subjects were assessed by using a crossover trial. The subjects were examined after an 8-h fast if they had normal fasting blood glucose concentrations. GER was calculated as the percentage change in the antral cross-sectional area 15–90 min after ingestion of 300 g rice pudding (GER1) or 300 g rice pudding and 6 g cinnamon (GER2).

Results: The median value ofGER1was 37%, and that of GER2 was 34.5%. The addition of cinnamon to the rice pudding significantly delayed gastric emptying and lowered the postprandial glucose response (P
0.05 for both). The reduction in the postprandial blood glucose concentration was much more noticeable and pronounced than was the lowering of the GER. The effect of cinnamon on satiety was not significant.

Conclusions: The intake of 6 g cinnamon with rice pudding reduces postprandial blood glucose and delays gastric emptying without affecting satiety. Inclusion of cinnamon in the diet lowers the postprandial glucose response, a change that is at least partially explained by a delayed GER.

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Paul Crawford. 2009. Effectiveness of cinnamon for lowering hemoglobin A1C in patients with type 2 diabetes: a randomized, controlled trial. J Am Board Fam Med. 22, 5: 507-512.

Abstract:

PURPOSE: Multiple trials in the past have shown conflicting results of whether cinnamon lowers glucose or hemoglobin A1C (HbA1C). The purpose of this study was to determine whether cinnamon lowers HbA1C in patients with type 2 diabetes. I performed a randomized, controlled trial to evaluate whether daily cinnamon plus usual care versus usual care alone lowers HbA1c.

METHODS: I randomized 109 type 2 diabetics (HbA1C >7.0) from 3 primary care clinics caring for pediatric, adult, and geriatric patients at a United States military base. Participants were randomly allocated to either usual care with management changes by their primary care physician or usual care with management changes plus cinnamon capsules, 1g daily for 90 days. HbA1c was drawn at baseline and 90 days and compared with intention-to-treat analysis. This study was approved by an institutional review board.

RESULTS: Cinnamon lowered HbA1C 0.83% (95% CI, 0.46-1.20) compared with usual care alone lowering HbA1C 0.37% (95% CI, 0.15-0.59).

CONCLUSIONS: Taking cinnamon could be useful for lowering serum HbA1C in type 2 diabetics with HbA1C >7.0 in addition to usual care.

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Richard Nahas and Matthew Moher. 2009. Complementary and alternative medicine for the treatment of type 2 diabetes. Canadian Family Physician 55: 591-6.

Abstract

OBJECTIVE; To review clinical evidence supporting complementary and alternative medicine interventions for improving glycemic control in type 2 diabetes mellitus.

QUALITY OF EVIDENCE; MEDLINE and EMBASE were searched from January 1966 to August 2008 using the term type 2 diabetes in combination with each of the following terms for specific therapies selected by the authors: cinnamon, fenugreek, gymnema, green tea, fibre, momordica, chromium, and vanadium. Only human clinical trials were selected for review.

MAIN MESSAGE; Chromium reduced glycosylated hemoglobin (HbA1c) and fasting blood glucose (FBG) levels in a large meta-analysis. Gymnema sylvestre reduced HbA1c levels in 2 small open-label trials. Cinnamon improved FBG but its effects on HbA1c are unknown. Bitter melon had no effect in 2 small trials. Fibre had no consistent effect on HbA1c or FBG in 12 small trials. Green tea reduced FBG levels in 1 of 3 small trials. Fenugreek reduced FBG in 1 of 3 small trials. Vanadium reduced FBG in small, uncontrolled trials. There were no trials evaluating microvascular or macrovascular complications or other clinical end points.

CONCLUSION; Chromium, and possibly gymnema, appears to improve glycemic control. Fibre, green tea, and fenugreek have other benefits but there is little evidence that they substantially improve glycemic control. Further research on bitter melon and cinnamon is warranted. There is no complementary and alternative medicine research addressing microvascular or macrovascular clinical outcomes.

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Kirkham, S.,  R. Akilen,  S. Sharma  and A. Tsiami. 2009.  The potential of cinnamon to reduce blood glucose levels in patients with type 2 diabetes and insulin resistance. Diabetes Obes Metab. 11, 12: 1100-13.

ABSTRACT

Aim: Cinnamon has a long history as an antidiabetic spice, but trials involving cinnamon supplementation have produced contrasting results. The aim of this review was to examine the results of randomized controlled clinical trials of cinnamon and evaluate the therapeutic potential amongst patients with diabetes and insulin-resistant patients, particularly the ability to reduce blood glucose levels and inhibit protein glycation.

Methods: A systematic electronic literature search using the medical subject headings 'cinnamon' and 'blood glucose' was carried out to include randomized, placebo-controlled in vivo clinical trials using Cinnamomum verum or Cinnamomum cassia conducted between January 2003 and July 2008.

Results: Five type 2 diabetic and three non-diabetic studies (total N = 311) were eligible. Two of the diabetic studies illustrated significant fasting blood glucose (FBG) reductions of 18–29% and 10.3% (p < 0.05), supported by one non-diabetic trial reporting an 8.4% FBG reduction (p < 0.01) vs. placebo, and another illustrating significant reductions in glucose response using oral glucose tolerance tests (p < 0.05). Three diabetic studies reported no significant results.

Conclusions: Whilst definitive conclusions cannot be drawn regarding the use of cinnamon as an antidiabetic therapy, it does possess antihyperglycaemic properties and potential to reduce postprandial blood glucose levels. Further research is required to confirm a possible correlation between baseline FBG and blood glucose reduction and to assess the potential to reduce pathogenic diabetic complications with cinnamon supplementation.

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Geil, P. and L. S.-Mc WHORTER. (2008). Dietary Supplements in the Management ofDiabetes: Potential Risks and Benefits. American Dietetic Association 108, 4: S59-S65.

Abstract; A wide range of products claiming to lower blood glucose levels or prevent and treat diabetes complications and comorbidities are marketed to the public. Yet many individuals with diabetes are reluctant to inform their health care providers of complementary therapy use. As the nutrition experts on diabetes care teams, registered dietitians, in conjunction with pharmacists, are uniquely positioned to encourage patients to communicate openly about their use of dietary supplements, provide safety and efficacy information about supplements, and discourage use of dangerous or ineffective products. Areas of concern with dietary supplement use include potential side effects, drug interactions, and lack of product standardization, in addition to the increased costs that patients may incur when they use ineffective therapies or delay treatment with proven therapeutic agents. The science behind dietary supplements is evolving and registered dietitians must fully understand the potential risks and benefits to advise their patients appropriately, yet respect their health care values and beliefs.

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Khan, A., M. Safdar, M. Muzaffar, A. Khan, K. N. Khattak and R. A. Anderson. 2003. Cinnamon Improves Glucose and Lipids of People With Type 2 Diabetes. Diabetes Care 26: 3215–3218.

OBJECTIVE— The objective of this study was to determine whether cinnamon improves blood glucose, triglyceride, total cholesterol, HDL cholesterol, and LDL cholesterol levels in people with type 2 diabetes.

RESEARCH DESIGN AND METHODS— A total of 60 people with type 2 diabetes, 30 men and 30 women aged 52.2
6.32 years, were divided randomly into six groups. Groups 1, 2, and 3 consumed 1, 3, or 6 g of cinnamon daily, respectively, and groups 4, 5, and 6 were given placebo capsules corresponding to the number of capsules consumed for the three levels of cinnamon. The cinnamon was consumed for 40 days followed by a 20-day washout period.

RESULTS— After 40 days, all three levels of cinnamon reduced the mean fasting serum glucose (18–29%), triglyceride (23–30%), LDL cholesterol (7–27%), and total cholesterol (12– 26%) levels; no significant changes were noted in the placebo groups. Changes in HDL cholesterol were not significant.

CONCLUSIONS— The results of this study demonstrate that intake of 1, 3, or 6 g of cinnamon per day reduces serum glucose, triglyceride, LDL cholesterol, and total cholesterol in people with type 2 diabetes and suggest that the inclusion of cinnamon in the diet of people with type 2 diabetes will reduce risk factors associated with diabetes and cardiovascular diseases.

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