Cinnamon is reputed to help maintain healthy blood sugar levels, a concern for people who have either pre-diabetic or type 2 diabetes. Evidence from human trials is generally consistent for a 10-percent decrease in fasting glucose, but not conclusive. Cinnamon should not be used in lieu of medical care. All of these trials were conducted using either powdered cinnamon or cinnamon extract in capsules, taken twice or three times a day. Using cinnamon on foods has not been tested in formal trials.
Significance
Millions of people in the U.S. have type 2 diabetes, also described as adult-onset diabetes. With diabetes, our bodies either do not produce enough insulin or are resistant to the insulin that is being produced. As a consequence, sugar from food does not get into the cells where it is needed, and instead is higher than normal in the blood. The normal range for fasting blood glucose--measured in the morning before breakfast--is 70 to 130 milligrams per deciliter, abbreviated as mg/dL. With diabetes, blood sugar is also elevated higher than normal after a meal. Untreated diabetes has serious consequences.
Identification of Cinnamon Types
"True" cinnamon is the species associated with Sri Lanka, formerly known as Ceylon. The formal species name is Cinnamomum zeylanicum. Other types of cinnamon are Chinese: C. cassia, Indonesian: C. burmanii and Vietnamese: C. loureiroi. All the clinical trials published in scientific journals were conducted with C. cassia. Most of the supplement products identify the type of cinnamon they contain. Cinnamon sold as spice is probably C. cassia because it is less expensive than C. zeylanicum. Or the spice may be a blend of the two.
Function
Exactly how cinnamon functions to help control blood sugar has not been determined. Theories range from the purely mechanical slowing of stomach emptying, which would have the result of not flooding the blood with sugar as quickly, to triggering more production of insulin and/or increasing sensitivity of the insulin receptors.
Evidence for Glucose Balance Benefits
One of the often cited studies in support for cinnamon was published by Dr. Alam Khan in the December 2003 issue of "Diabetes Care." This human trial tested 1, 3 and 6 grams of powdered cinnamon per day, in capsules. Fasting blood sugar dropped 24 percent after 40 days. The higher doses did not have a stronger effect. Although the subjects were type 2 diabetes patients taking medication to control their diabetes, their average starting blood glucose was 216 mg/dL--very high. For six subsequent clinical trials of pre-diabetic or type 2 diabetes patients with better-controlled blood sugar, the effect of consuming one-third to 1.5 grams of cinnamon for 6 to 12 weeks averaged a 9.8-percent decrease in fasting blood sugar.
Warnings
Two of the clinical trials used powdered cinnamon in capsules and had only modest impact; decreases of 7.5 percent and 5.3 percent, respectively. The other four trials conducted since Khan's 2003 report used a cinnamon extract that claims to increase the concentration of the active ingredient. Thus, the evidence for powdered cinnamon is not strong. Khan also claimed lowering of cholesterol and triglycerides, but none of the subsequent clinical trials have been able to repeat this finding.
References
- "Diabetes Care"; Cinnamon improves glucose and lipids of people with type 2 diabetes; A. Khan et al.; Dec. 2003.
- "Journal of American College of Nutrition"; Antioxidant effects of a cinnamon extract in people with impaired fasting glucose that are overweight or obese; A. M. Roussel et al.; 2009.
- "Fertility and Sterility"; The effect of cinnamon extract on insulin resistance parameters in polycystic ovary syndrome: a pilot study; J. Wang et al.; 2007.
- "Journal of the International Society for Sports Nutrition"; Effects of a water-soluble cinnamon extract on body composition and features of the metabolic syndrome in pre-diabetic men and women; T. Ziegenfuss et al.; Aug. 7, 2006.
- "European Journal of Clinical Investigation"; Effects of a cinnamon extract on plasma glucose, HbA, and serum lipids in diabetes mellitus type 2; M. Wolters et al.; May 2006.
