Controversies surrounding the clinical potential of cinnamon for the management of diabetes

Abstract

Obesity levels have increased significantly in the past five decades and are predicted to continue rising, resulting in important health implications. In particular, this has translated to an increase in the occurrence of type II diabetes mellitus (T2D). To alleviate associated problems, certain nutraceuticals have been considered as potential adjuncts or alternatives to conventional prescription drugs. Cinnamon, a commonly consumed spice originating from South East Asia, is currently being investigated as a potential preventative supplement and treatment for insulin resistance, metabolic syndrome and T2D. Extensive in vitro evidence has shown that cinnamon may improve insulin resistance by preventing and reversing impairments in insulin signalling in skeletal muscle. In adipose tissue, it has been shown that cinnamon increases the expression of peroxisome proliferator-activated receptors including, PPARγ. This is comparable to the action of commonly used thiazolinediones, which are PPAR agonists. Studies have also shown that cinnamon has potent anti-inflammatory properties. However, numerous human clinical trials with cinnamon have been conducted with varying findings. While some studies have showed no beneficial effect, others have indicated improvements in cholesterol levels, systolic blood pressure, insulin sensitivity and postprandial glucose levels with cinnamon. However, the only measurement consistently improved by cinnamon consumption is fasting glucose levels. While it is still premature to suggest the use of cinnamon supplementation based on the evidence, further investigation into mechanisms of action is warranted. Apart from further characterization of genetic and epigenetic changes in model systems, systematic large-scale clinical trials are required. In this study, we discuss the mechanisms of action of cinnamon in the context of T2D and we highlight some of the associated controversies.

Herbal Therapies for Type 2 Diabetes Mellitus: Chemistry, Biology, and Potential Application of Selected Plants and Compounds

“…Cinnamon has traditionally been used for rheumatism, wounds, diarrhea, headaches, and colds [136]. Recently, extensive studies have been performed on the action of cinnamon on diabetes and metabolic syndrome [135].…”

Potential therapeutic value of TRPV1 and TRPA1 in diabetes mellitus and obesity

“…The controversy regarding effects of cinnamon undoubtedly exists and further studies required determining the patient population which could benefit from cinnamon supplementation. Detailed review of findings regarding cinnamon interventions in diabetes mellitus can be found in other papers (35, 36). …”

Trimer procyanidin oligomers contribute to the protective effects of cinnamon extracts on pancreatic β-cells in vitro

“…For example, some studies reported that cinnamon supplementation did not have any significant effects on type 2 diabetic patients [9,10] . Cinnamon is produced from the bark of multiple species of Cinnamomum, which contains a variety of compounds, such as cinnamaldehyde, eugenol, and polyphenols [11] . Recently, active water-soluble components were isolated and found to Trimer procyanidin oligomers contribute to the protective effects of cinnamon extracts on pancreatic β-cells in vitro 1084 www.nature.com/aps Sun P et al Acta Pharmacologica Sinica mediate beneficial effects on glucose metabolism [12][13][14] .…”