Cinnamon as a Natural Adjunct in Glycemic Control: A Review of Current Evidence and Underlying Mechanisms

Abstract

Type 2 diabetes mellitus (T2DM) represents one of the most significant public health issues of the twenty-first century. It is characterised by chronic hyperglycaemia resulting from insulin resistance, impaired insulin secretion, and progressive beta-cell dysfunction. Its prevalence continues to rise globally, driven by sedentary lifestyles, unbalanced diets, and an ageing population, imposing significant socioeconomic and healthcare burdens. Conventional treatment strategies based on pharmacological therapy, dietary modifications, and increased physical activity frequently fail to achieve sustained glycaemic targets, prompting growing interest in complementary and natural interventions. Among various plant-derived substances, cinnamon (Cinnamomum verum J. Presl) has emerged as a promising adjunctive agent in glycaemic control. It contains multiple bioactive constituents, such as cinnamaldehyde, eugenol, and polyphenolic proanthocyanidins, which exert a range of effects on glucose and lipid metabolism. These compounds enhance insulin receptor activity, facilitate glucose uptake in peripheral tissues, inhibit intestinal α-glucosidase and α-amylase enzymes, and reduce oxidative stress and inflammatory signalling. Through these mechanisms, cinnamon supplementation may improve insulin sensitivity, lower fasting blood glucose, and attenuate postprandial hyperglycaemia. Evidence from numerous clinical trials and meta-analyses provides evidence that daily supplementation with 1-6 g of cinnamon over several weeks can produce modest yet statistically significant reductions in fasting plasma glucose, HbA1c, triglycerides, and LDL cholesterol. Furthermore, experimental findings suggest beneficial effects on hepatic enzyme activity and oxidative balance in patients with T2DM. Nevertheless, inconsistencies in reported outcomes are attributed to differences in study design, cinnamon species (C. verum versus C. cassia), and formulation (powder, extract, or capsule). Safety considerations, particularly with regard to the coumarin content of C. cassia, support the preferential use of C. verum in clinical applications. From a therapeutic perspective, cinnamon supplementation is a safe, affordable, and easily accessible complementary strategy that could enhance conventional antidiabetic therapy, improve metabolic stability, and promote patient adherence. Therefore, integrating cinnamon into comprehensive diabetes management alongside pharmacotherapy, dietary regulation, and lifestyle modification may contribute to improved long-term clinical outcomes.