In vitro and in vivo animal studies have reported strong insulin-like or insulin-potentiating effects after cinnamon administration. Recently, a human intervention study showed that cinnamon supplementation (1 g/d) strongly reduced fasting blood glucose concentration (30%) and improved the blood lipid profile in patients with type 2 diabetes. The objective of this study was to investigate the effects of cinnamon supplementation on insulin sensitivity and/or glucose tolerance and blood lipid profile in patients with type 2 diabetes. Therefore, a total of 25 postmenopausal patients with type 2 diabetes (aged 62.9 +/- 1.5 y, BMI 30.4 +/- 0.9 kg/m2) participated in a 6-wk intervention during which they were supplemented with either cinnamon (Cinnamomum cassia, 1.5 g/d) or a placebo. Before and after 2 and 6 wk of supplementation, arterialized blood samples were obtained and oral glucose tolerance tests were performed. Blood lipid profiles and multiple indices of whole-body insulin sensitivity were determined. There were no time x treatment interactions for whole-body insulin sensitivity or oral glucose tolerance. The blood lipid profile of fasting subjects did not change after cinnamon supplementation. We conclude that cinnamon supplementation (1.5 g/d) does not improve whole-body insulin sensitivity or oral glucose tolerance and does not modulate blood lipid profile in postmenopausal patients with type 2 diabetes. More research on the proposed health benefits of cinnamon supplementation is warranted before health claims should be made.