Does Cinnamon Conflict With Metformin?
I've heard that cinnamon helps control blood sugar. How much truth is there to this, and would it in any way conflict with me taking metformin? Toni Cheary, Claremore, Oklahoma
Roger P. Austin, MS, RPH, CDE, responds:
Cinnamon has been used as a spice and for medicinal purposes for thousands of years. Medicinal uses have varied over the centuries and include a wide variety of maladies such as gastrointestinal disorders, chronic bronchitis, rheumatism and arthritis, and toothaches. More recently, there has been a flurry of interest in the effects of cinnamon on blood glucose levels. A number of scientific papers have looked more closely at these effects, but the conclusions are mixed at best. Some studies showed that cinnamon lowered fasting blood glucose, total cholesterol, and LDL ("bad") cholesterol. Other studies showed no effect on insulin sensitivity, blood glucose levels, or cholesterol.
This serves to illustrate one of the classic problems with the widespread interest in "natural" or "herbal" remedies in treating human diseases. First, there are several different sources of cinnamon. Cinnamon can be derived from the bark of several species of cinnamon trees or from their leaves; there are a variety of processes used to extract and to refine these products as well. Cinnamon comes from various countries, and is grown in different climates and at different altitudes, all of which can affect the content of the active compounds. Most natural sources of cinnamon are from Asia, including China, Vietnam, Indonesia, and Sri Lanka. Thus, when one purchases "cinnamon," there is no international standard for the content of active ingredients that may have effects on blood glucose or cholesterol. Furthermore, the Food and Drug Administration does not regulate the content of active ingredients in any of the many herbal products sold in the United States.
So, could the regular use of cinnamon (other than as a spice or flavoring) conflict with your use of metformin? Yes, it could, but we have no way of predicting to what degree, if at all. In contrast to the lack of regulation of herbal remedies, the FDA does strictly supervise and monitor pharmaceuticals manufactured and distributed in the United States, for both safety and efficacy. When you take your regular dose of metformin, you can reasonably expect a consistent effect on your blood glucose levels. You do not have the same assurance when you choose to use an unregulated substance such as cinnamon.