Now, I have third thoughts.
A meta-analysis published yesterday shows that cinnamon -- especially cinnamon extract -- produces a modest but statistically signification reduction of fasting blood glucose. The study, “Cinnamon Intake Lowers Fasting Blood Glucose: Meta-Analysis,” appears in the September 2011 issue of the Journal of Medicinal Food, and the abstract is online.
The authors are Paul A. Davis of the Department of Nutrition, University of California, Davis, and Wallace Yokoyama of the Western Regional Research Center, U.S. Department of Agriculture. Dr. Davis kindly sent me the full-text of the study on my request.
Several of the earlier studies didn’t “discretely report fasting blood glucose levels,” the new meta-analysis says. Another one studied people with type 1 diabetes, but “cinnamon decreases insulin resistance, which is not a mechanism of type 1 diabetes.” The new meta-analysis includes eight studies of cinnamon, including new ones that tested the effect of water extracts of cinnamon and had larger study populations.
The new meta-analysis says that both the type of cinnamon and how people prepare it is important. All but one the eight studies in the meta-analysis used cassia cinnamon. The other one didn’t specify the type of cinnamon.
Preparing the cinnamon as a water extract “may be preferable.” A water extract works as well if not better than whole cinnamon, and it avoids problems like oral lesions and mutagenicity that come with using lots of cinnamon.
In two places the meta-analysis calls the improvement in blood glucose level “modest.” But it also states that the improvement is “of the same order of magnitude as for metformin.” That’s enough of an improvement for us to stop thinking about cinnamon as only a popular cooking spice, but instead consider using it as an effective medicinal food.