Effect of cinnamon on glucose and lipid levels in non insulin-dependent type 2 diabetes.

Interest in cinnamon as a potentially useful treatment for type 2 diabetes began with the discovery almost 20 years ago of cinnamon’s insulin-sensitizing properties (1). Numerous in vitro and in vivo studies have elucidated cinnamon’s effect on insulin signal transduction (2– 6). A study in diabetic mice showed that cinnamon lowered blood glucose, total cholesterol, and triglyceride levels while raising HDL cholesterol levels (7). The first clinical trial to evaluate the effect of cinnamon in individuals with type 2 diabetes was conducted in Pakistan (8). It showed that cinnamon powder (Cinnamomum cassia), taken over a 40day period, reduced mean fasting serum glucose (18 –29%), triglyceride (23– 30%), LDL cholesterol (7–27%), and total cholesterol (12–26%) levels. Three different doses of cinnamon were administered: 1, 3, and 6 g daily. All were equally effective. These findings led to widespread cinnamon use, although no study had yet evaluated the effects of cinnamon in Western diabetic populations with likely differences in diet, BMI, baseline glucose levels, and prescribed medication. We report the first U.S. study examining the effects of cinnamon on glucose and lipid levels in subjects with type 2 diabetes. RESEARCH DESIGN AND METHODS — Participants were recruited through e-mail announcements to campus employees and through an article in the local newspaper. Individuals of any age with type 2 diabetes, based on criteria from the American Diabetes Association (9), were eligible for the study. Exclusion criteria included insulin use, consumption of nondietary cinnamon supplements, A1C 6.0%, and acute illness. Subjects were withdrawn if any of the following medicines were initiated, discontinued, or adjusted during the study: sulfonylureas, meglitinides, metformin, thiazoledinediones, -glucosidase inhibitors, exenatide, hydromethylglutarylCoA reductase inhibitors, ezetimibe, niacin, or fibric acid derivatives. Enrolled subjects were stratified by sex and randomized to receive either cinnamon (C. cassia) or placebo (wheat flour). Investigators and subjects were blinded to group assignment and to capsule content. Each capsule contained 500 mg product. Subjects were instructed to ingest one capsule with breakfast and one with dinner for 3 months. Compliance was assessed by capsule count. Follow-up visits were scheduled at 1, 2, and 3 months. Fasting glucose, cholesterol (total, LDL, and HDL), triglyceride, and insulin levels were measured at each visit. A1C was measured at baseline and at 3 months. Dietary patterns were monitored monthly using a 3-day food journal. An intention-to-treat analysis was conducted. Outcomes were analyzed using a general linear model for the threeway ANOVA (two treatments 2 sexes 4 visits) with repeated measures on the time factor. Significance was set at 0.05. We estimated that changes ranging from 11.5 (A1C) to 24.7% (triglycerides) could be detected with 80% power. For each variable, detectable change was within the range found by Khan et al. (with the exception of A1C, which was not measured by Khan et al.) (8).