Several studies have been done on the effectiveness of reducing A1c levels and blood lipids and increasing insulin sensitivity by adding cinnamon to the diet.

OBJECTIVE—The objective of this study was to determine whether cinnamon improves blood glucose, triglyceride, total cholesterol, HDL cholesterol, and LDL cholesterol levels in people with type 2 diabetes.

RESEARCH DESIGN AND METHODS—A total of 60 people with type 2 diabetes, 30 men and 30 women aged 52.2 ± 6.32 years, 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 were given placebo capsules corresponding to the number of capsules consumed for the three levels of cinnamon. The cinnamon was consumed for 40 days followed by a 20-day washout period.

RESULTS—After 40 days, all three levels of cinnamon reduced the mean fasting serum glucose (18–29%), triglyceride (23–30%), LDL cholesterol (7–27%), and total cholesterol (12–26%) levels; no significant changes were noted in the placebo groups. Changes in HDL cholesterol were not significant.

CONCLUSIONS—The results of this study demonstrate that intake of 1, 3, or 6 g of cinnamon per day reduces serum glucose, triglyceride, LDL cholesterol, and total cholesterol in people with type 2 diabetes and suggest that the inclusion of cinnamon in the diet of people with type 2 diabetes will reduce risk factors associated with diabetes and cardiovascular diseases.

http://care.diabetesjournals.org/co...26/12/3215.full

One important thing to note is that cinnamomum cassium was used. NOT cinnamomum vericum or Ceylon Cinnamon.

Cinnamomum cassium, which is the every day garden variety of cinammon that is most common in North America, also has potentially dangerously high concentrations of coumarin, which can cause severe liver damage when taken in large amounts, such as 1 teaspoon per day. Ceylon Cinnamon, on the other hand, seems to have the same beneficial effects while containing very little coumarin.

If you are going to consume cinnamon on a regular basis to take advantage of its beneficial effects, please make sure that you find a source of Ceylon Cinnamon, or Cinnamomum Vericum.

Major brands of spices, such as McCormick, only sell the cassia variety.