Cinnamon and Blood Glucose

The other day I was at Sam's Club, pushing my cart past the supplement section on the way to the meat counter. As I glanced at the shelves, I noticed something new. There was a bottle containing 500 mg capsules of cinnamon (specifically, ground Cinnamomum cassia bark). On the one hand, I had heard that cinnamon was able to improve blood glucose levels, but I hadn't read any of the papers. On the other hand, my fasting blood glucose levels had been in the 100 mg/dl range for a while, even though I eat less than 10 grams of carbs per day. I had been taking chromium supplements, but they didn't seem to have much of an effect. Since the cinnamon capsules weren't particularly expensive, I decided to take a chance and I bought them.

When I got home, I pulled up some of the scientific papers on cinnamon and saw that a reasonable dose would be about 1.5 grams per day. I took a capsule at breakfast, lunch and bedtime and the next morning my blood glucose was 95. To my amazement, the readings continued near that value throughout the week. I told a prediabetic friend about this, and she decided to try it as well. She too noticed a drop of about 5-10 mg/dl in her blood glucose levels. Next, my husband told one of the people at work about my experience. She has type 2 diabetes and is taking both oral hypoglycemic agents and a bit of insulin. She tried the cinnamon capsules and her blood glucose levels fell by 50 mg/dl.

Alrighty then. I decided it was time to read the scientific papers and see if there was anything to these anecdotal experiences. This blogpost will summarize my findings, such as they are.

In 2003 a paper by Khan et al. appeared in Diabetes Care. It described a group of 60 people who had type 2 diabetes and were being treated with sulfonylurea drugs. They were divided into six groups, with the first three taking 1, 3 or 6 grams of cinnamon daily while the second three were given placebo capsules of 1, 3 or 6 grams of wheat flour. After 40 days of treatment, the placebo groups experienced no change in fasting serum glucose, but the three treatment groups experienced decreases of 25%, 18% and 29%. There did not appear to be a dose-response because all three levels of cinnamon intake produced similar results.

This result was not totally unexpected because cinnamon had been observed to have insulin-enhancing activity in laboratory studies. With that in mind, several groups performed prospective clinical trials with cinnamon in human beings. Five of these studies were reviewed by Baker et al. in 2008. They concluded that the use of cinnamon did not significantly alter hemoglobin A1c or fasting blood glucose in patients with type 1 or type 2 diabetes.

However, other studies showed that there was an improvement in blood glucose with cinnamon. Zeigenfuss et al. used an aqueous cinnamon extract to treat prediabetic subjects and saw no effect at six weeks, but at twelve weeks observed an 8.4% drop in fasting blood glucose. In 2007 Wang et al. studied women with polycystic ovary syndrome (PCOS), a hormone disorder associated with insulin resistance. After eight weeks of treatment with a cinnamon extract, these women experienced significant declines both in fasting blood glucose and in two measures of insulin resistance. In 2009 Paul Crawford studied a heterogenous group of poorly controlled type 2 diabetics in a primary care setting. Their medications and dietary recommendations were left unchanged, but the treatment group received an add-on dose of 1 gram of cinnamon per day in an open-label study. After 90 days, the treatment group had significantly lowered its hemoglobin A1c from 8.47 to 7.64.

A 2008 lecture by Richard A. Anderson gives some insight into the possible mechanisms of cinnamon enhancement of insulin sensitivity. When insulin binds to its receptor, it starts a signaling cascade that begins with the autophosphorylation of the insulin receptor. In the presence of cinnamon extracts, this autophosphorylation is more robust. Not only that, cinnamon inhibits the dephosphorylation of the insulin receptor, which further enhances the signal. Cinnamon also increases the amount of insulin receptor proteins and of other proteins in the insulin signaling pathway. Cinnamon is not a substitute for insulin, but it does make insulin signaling more sensitive to the insulin that is present in the blood.

In summary, it appears that supplementation with cinnamon may provide a small but significant improvement in insulin sensitivity. It appears to have a greater influence in people with poorly controlled blood sugar, especially in those who are taking drugs that enhance insulin secretion by the pancreas. In people who are pre-diabetic, the glucose-lowering effect seems to be less. In fact, when cinnamon is given to normal subjects, it does not decrease their blood glucose, but instead reduces their postprandial serum insulin. Although the anecdotal experiences I related at the beginning would suggest that cinnamon has an immediate effect on blood glucose, from the scientific literature, it appears that it may take up to 12 weeks to exert its actions.

Even though cinnamon is found in practically every kitchen in the Western world, it is important to note that some people are allergic to cinnamon. If you decide to try cinnamon supplementation, be careful to look for rashes, inflammation of the mucous membranes or even trouble with breathing. Be sure to discontinue the cinnamon if any of these symptoms occur.

That said, it appears that supplementation with cinnamon may be helpful as part of a strategy to normalize blood glucose levels.