Cinnamon, one of the oldest and most commonly used spices, is long known as a good anti-bacterial and antioxidant agent. Perhaps it might help millions of sufferers of type 2 diabetes, too. A research conducted at the Beltsville Human Nutrition Research Center in Maryland, USA, and the University of Peshawar, Pakistan, published in 2003, dealt with this question.
Although the causes of type 2 diabetes and cardiovascular diseases are multifactorial, dietary intake certainly plays a role in the frequency and severity of these diseases. The dietary components which might be of benefit in prevention and treatment have not been clearly defined, but botanical products seem to belong to these components. They can improve glucose metabolism and the overall condition of individuals with diabetes, not only by reducing blood glucose but also by improving lipid metabolism, antioxidant status, and capillary function. A number of medicinal and/or culinary herbs have been reported to lead to hypoglycaemic effects in patients with diabetes, triggering the insulin activity in vitro, and cinnamon is one of these. Cinnamon (Cinnamomum sp.) is the dried inner bark of the cinnamon trees.
Because insulin has an important role in lipid metabolism, too, the researchers from Maryland and Pakistan considered that consumption of cinnamon would lead not only to improved blood glucose, but also lipid levels. Therefore, this study was designed to determine whether there is a reaction of clinical figures related to diabetes and cardiovascular diseases (the prevalence of which is increased from two- to fourfold in people with type 2 diabetes).
The trial investigated whether cinnamon improves levels of blood glucose, triglycerides, total cholesterol, HDL cholesterol, and LDL cholesterol in type 2 diabetes. An overall of 60 patients 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 got placebo capsules. Besides, people had their normal diet and medications. Cinnamon intake lasted for 40 days followed by a 20-day washout period. Results after 40 days showed that all three dosages of cinnamon had lead to a significant decrease in:
- mean fasting serum glucose (18–29%)
- triglycerides (23–30%)
- LDL cholesterol (7–27%)
- total cholesterol (12–26%)
No significant changes were noted in the placebo groups. Changes in HDL cholesterol were not significant. The response was not dose-dependent, meaning that also small amounts of cinnamon do as good as bigger ones. The lower blood glucose and lipid levels were maintained during the cinnamon-free interval, too, indicating that it would not be necessary to intake cinnamon every day.
The mode of action of cinnamon in reducing blood glucose still has to be determined. It is known that in type 2 diabetes, insulin sensitivity and glycogen synthesis are reduced. The altered activity of enzymes playing important roles in glycogen synthesis is involved in some cases of diabetes. Extracts of cinnamon can activate glycogen synthesis, increased glucose uptake, and inhibited glycogen synthase kinase-3, an enzyme leading to decreased activity of the insulin receptor. Cinnamon has been shown also to activate insulin receptor kinase and to inhibit dephosphorylation of the insulin receptor, all effects leading to an increased insulin sensitivity.
Because cinnamon would not increase the caloric intake, patients with type 2 diabetes or subjects with elevated glucose, triglyceride, LDL cholesterol, or total cholesterol levels may have a benefit from the regular inclusion of cinnamon in their daily diet. In addition, cinnamon may have positive effects for the general population, too, to prevent and/or control elevated glucose and blood lipid levels, so the final conclusion of the researchers.