Pharmacist Scott Gavura writes at Science Based Medicine:
Given the consequences of diabetes, self-management is something I want to encourage, not discourage. Without a commitment from the patient to take an active role in managing their diabetes, any treatment plan is doomed to fail. So is self-treatment with dietary supplements a wise idea? There’s an array available, and patients regularly ask about the latest treatment “Big Pharma doesn’t want you to know about”. That treatment used to be chromium. Ginseng was popular for a time, too. Fenugreek and bitter melon are used as well. One of the most persistently popular treatments is cinnamon. Like any other herbal remedy, most sources will tell you that it’s been used for “thousands of years” as a medicinal herb. As a treatment for diabetes, I have my doubts. While reports of diabetes go back to 1552 BCE, the ability to measure the effectiveness of any diabetes treatment only goes back a few decades. Interest in cinnamon as a treatment seems to have started with in vitro tests but gained some plausibility in 2003, when a study from Alam Khan suggested several grams of cassia cinnamon per day could lower fasting blood glucose. Khan randomized Type 2 diabetes to 1g, 3g, or 6g of cinnamon for 40 days. All three groups improved their fasting blood glucose, and blood lipid levels, but there was no effect on A1C.Like trials with any other supplement or herbal product, the primary question we must answer is “What exactly was studied?” The cinnamon you have in your kitchen may be a single species of plant or a mix of different cultivars. Ceylon cinnamon (Cinnamommum verum) is more commonly found in the West. Cassia cinnamon (Cinnamomum aromaticum) is the version of cinnamon that’s been studied in trials. The chemical hydroxychalcone has been identified as a potential active ingredient, which is believed to modify the sensitivity of cells to insulin, enhancing their uptake. If that’s the true mechanism of action, then it would work in a manner similar to that of the drugs Avandia, Actos, and metformin (Glucophage). Given the active ingredient (or ingredients) have not yet been definitively isolated, the issue of studying cinnamon is problematic. There’s no way to assess the potency of any batch, which complicates any evaluation. And that may be a reason why the research with cinnamon is inconsistent, and on balance, not impressive.
While the Khan study looked promising, supplementary studies have failed to consistently show beneficial effects.
Source: How effectively does cinnamon treat diabetes? – Science-Based Medicine