Control Your Blood Sugar with Cinnamon

Cinnamon Improves
Glucose Tolerance and
Insulin Sensitivity

Study in healthy young men adds more evidence that
supplementing with this spice is good for us
By Will Block

First appeared in the January 2008 issue

What is the difference between a taxidermist and a
tax collector? The taxidermist takes only your skin.

— Mark Twain

arning: The first part of this article is about something that could make your skin crawl: taxes. We’re not grinding a political ax, just making a point about economics and, via that, medical research. Much of this research is devoted to finding ways to forestall something else that we hate to contemplate: death. (Hmm, death and taxes—isn’t there some old saying about those two?)

History shows that tax increases have tended to hurt our economy by stifling consumer spending and business investment, whereas tax cuts have tended to help the economy by stimulating these actions. Although one might expect a lower tax rate to produce lower tax revenues, the opposite is usually true, owing to the surge in economic growth that tax cuts typically unleash (for a dramatic example, just look at the last few years). Isn’t economics fun?

Replication, the Impossible Dream

For some it is, perhaps, but it’s frustrating too—it’s not called the “dismal science” for nothing. Of course, economics is not a science at all. Science deals with natural phenomena, not human institutions, and it’s meaningful only to the extent that it can make predictions that can be proved or disproved experimentally, with results that can be replicated. Ah, there’s the rub.

In that regard, economics is hamstrung: no set of human circumstances (economic, social, political, demographic, biological, etc.) that has ever existed will ever exist again, so no economic “experiment” (much less the results) can be replicated. Hence nothing can be predicted with certainty, and nothing can be proved in any scientific sense. One can predict only tendencies and probabilities that are based on: (1) theoretical reasoning; (2) the results of experiments whose applicability to real life is imperfect at best; and (3) statistical analyses of the consequences of similar (but never identical) real-life events.

Medicine—Not Really Science, but a Great Offspring

What do you know—that describes much of medical research pretty accurately (which, by the way, is why medicine is not considered a science either, although most of it is firmly grounded in science). Here we’re interested in the last of the three factors mentioned above: real-life events, i.e., the results of clinical trials of nutritional supplements in human beings, as opposed to experiments with lab animals or with cells in petri dishes.

But no two clinical trials are ever the same. Even if a trial were repeated using the same people and following the same protocol, the results would probably be somewhat different. The people would be a little older, and the circumstances of their lives would have changed somewhat, so they might not respond to the supplement in quite the same way. Not to mention that knowing the results of the first trial would surely bias their responses in the second trial (mind over matter). Furthermore, their diet might have changed a little, and the weather would probably be different (weather can affect people’s health and mood in subtle ways). And . . . well, you get the idea.

Cinnamon and the Numbers Game

Possible, not probable.
So what do researchers do when faced with inconsistent or contradictory results from different clinical trials on the same supplement? They use their best judgment in weighing the evidence. If one trial seems procedurally solid but another one seems weak, the first one “wins,” in a sense. If nine out of ten trials that all seem solid produce similar results, who wouldn’t be inclined to believe in the nine and discount the one as a probable fluke? Although it’s possible that the nine were wrong and the one was correct, it’s very unlikely.*

*We’re reminded of the common advertising pitch, “Nine out of ten doctors recommend new, improved KureAll for whatever ails you.” How come we never hear from that tenth doctor? What if he or she is the really smart one?

But what if it’s only two out of three studies that show similar results? That leaves more room for doubt, doesn’t it? Such a situation occurred recently with regard to cinnamon. In laboratory and animal studies, that delightful spice had been found to help regulate blood sugar (glucose) levels, which it does by acting like insulin, the hormone responsible for transporting glucose from the bloodstream into our cells. The trouble, however, was that, of the three human clinical trials with cinnamon, only two confirmed this discovery—the third did not. We’ll see shortly what happened next.

Cinnamon Mimics Insulin

With advancing age, and especially with obesity and an inactive lifestyle, we can experience significant impairment of our glycemic control—the ability to hold blood glucose levels down within the normal (healthy) range. This impaired condition is called insulin resistance. The body responds by generating more and more insulin to make up for the cells’ decreasing sensitivity to the hormone. Eventually, however, even this compensatory mechanism may fail, resulting in type 2 diabetes, in which the patient suffers chronically elevated levels of blood glucose and insulin. Both of these conditions are exceedingly harmful.

Thus, anything that can help with insulin function is beneficial—and that’s where cinnamon comes in. The active agent is believed to be a group of flavonoids called procyanidins (type A), which are found in the water-soluble portion of cinnamon powder.* They act as insulin mimetics (i.e., they mimic insulin in biochemical processes), not only in facilitating glucose transport into our cells but also in promoting the synthesis of glycogen, a glucose polymer that’s stored in our liver and muscles as a reserve supply of energy. (Those are but two of insulin’s many important biological roles; see the sidebar for more.)

*The fat-soluble portion of cinnamon contains certain compounds, such as the anticoagulant coumarin, that could be harmful in large amounts. Supplemental cinnamon is best taken, therefore, as the water-soluble extract, which does not contain these compounds.

Insulin Wears Many Hats

Forget about insulin resistance for a moment. In a healthy body, not all of the cells respond to insulin in the first place, because many (including those of the brain) can absorb glucose without the need for insulin. The cells that do require insulin are those of the liver, the skeletal muscles, the heart, and adipose tissue (fat). In these tissues, insulin has at least a dozen distinct metabolic effects. They occur via either its promotion of or its inhibition of certain biochemical pathways (a pathway is a sequence of chemical reactions leading to a certain effect).

You knew that insulin plays a life-or-death role as the body’s regulator of blood glucose levels, and you may have known that it also regulates the storage of excess glucose in the form of glycogen. But did you know that excess glucose can also be converted to fatty acids, which are the immediate precursors of fats (also called triglycerides), and that insulin plays a role there too? Fatty acids are the second most important source of chemical energy for our cells.

In addition to facilitating the transport of fatty acids into cells that need them as fuel, insulin promotes their conversion to fat for storage in adipocytes (fat cells). Like glycogen reverting back to glucose on demand, fat acts as a reserve source of energy by reverting back to fatty acids on demand. The trouble is, if we overeat and don’t exercise enough, the supply of fat will exceed the demand for energy. That can lead to obesity, the main cause of insulin resistance, which can lead to diabetes.

Insulin does not act alone in the regulation of glucose, glycogen, fatty acids, and fat—many other compounds, including other hormones, are also involved, but we can’t go into all that here. Let’s just list insulin’s direct and indirect functions as they are presently known:

Insulin Promotes

  • Glucose transport
  • Glucose oxidation
  • Glycogen synthesis
  • Fatty acid synthesis
  • Fat synthesis
  • Amino acid transport
  • Protein synthesis
  • Potassium transport

Insulin Inhibits

  • Gluconeogenesis (the production of glucose from noncarbohydrates, such as protein or fat)
  • Glycogenolysis (the breakdown of glycogen to glucose)
  • Lipolysis (the breakdown of fat to fatty acids)
  • Ketogenesis (the production of ketones, a characteristic of diabetes)
  • Proteolysis (the breakdown of proteins)

Despite its tendency to inhibit proteolysis, insulin (a protein) is itself rapidly broken down by proteolytic enzymes, giving it a half-life in the blood of less than half an hour. The liver alone is capable of destroying about half of the insulin passing through it on its way from the pancreas to the body’s tissues. The fact that cinnamon can assist insulin in at least some of the functions listed above is a gift from Mother Nature.

Daily Cinnamon Improves Fasting Glucose Levels
(2 out of 3)

As of mid-2006, there were three clinical trials of cinnamon with humans. The first of these, conducted in Pakistan and published in 2003, showed that daily supplementation with 1, 3, or 6 g of whole cinnamon powder reduced fasting blood glucose levels by 18–29% in middle-aged patients with type 2 diabetes.1 (The results showed no long-term advantage of the two higher doses over the 1-g/day dose.) Cinnamon also reduced the patients’ cholesterol levels. (See “Cinnamon Reduces Blood Sugar and Cholesterol Levels” in the February 2004 issue.)

The results for glucose were confirmed in 2006, in a study done in Germany.2 Here a water-soluble extract of cinnamon was used, in an amount equivalent to 3 g/day of whole cinnamon powder. Again the patients were type 2 diabetics, and again they experienced substantial declines in their fasting glucose levels, albeit not by as much (10%) as in the Pakistani study. There was no effect on cholesterol levels, however. (See “Cinnamon Reduces Blood Sugar in Diabetic Patients” (July 2006.)

The German authors speculated that the smaller reduction of glucose levels they observed was because their patients’ diabetes was under better control to begin with than that of the Pakistani patients—the latter had more room for improvement, so to speak. They concluded that cinnamon supplementation is likely to be more effective in patients with more poorly controlled diabetes.

So far, so good—but now the waters get muddied. Also in 2006, a group of researchers in the Netherlands published yet another study of the same kind, this time using 1.5 g/day of whole cinnamon powder in a group of postmenopausal diabetic women.3 The results showed that cinnamon had no effect whatever, either on blood glucose levels or on cholesterol levels. Uh-oh.

Fourth Study Uses a Single Dose . . .

Even before the German and Dutch studies had been published, two researchers in England had begun what was to become the fourth study on this matter, using seven sedentary but otherwise healthy young men, average age 26.4 In what is called a randomized crossover design, each of the men served as his own control, by taking first cinnamon and then (after a suitable “washout” period) a placebo, or vice versa.

Unlike the other studies, in which prolonged daily supplementation with cinnamon was employed, this study was designed to measure the effects on fasting glucose levels of a single dose of cinnamon (5 g of the whole powder, in a capsule that was indistinguishable from the placebo). The test used was the standard oral glucose tolerance test (OGTT), in which the patient drinks a glass of water containing 75 g of pure glucose. The blood glucose concentration promptly begins to rise, peaks in about 30 minutes, and then (in healthy individuals) returns to normal within about 2 hours from the start.

In patients with insulin resistance or diabetes, the peak glucose concentration is higher, and the return to baseline (which may be higher than normal) takes longer. Thus, the patients’ blood contains more glucose (and insulin) for longer periods, which is highly detrimental to health.

. . . Which Provides Immediate, Sustained Benefits

When the men were given cinnamon along with the glucose at the start of the OGTT, the result was blood glucose levels that were 13% lower than when placebo was given. Even when the cinnamon was given 12 hours before the OGTT, the reduction was 10%. These are significant reductions (but the difference between them was not statistically significant, i.e., the data indicated that it didn’t matter when the cinnamon was taken, because its effect was sustained for at least 12 hours). The trial was repeated three times at 5-day intervals, with the same results each time.

The researchers also calculated the subjects’ insulin sensitivity index, a measure of how well their cells responded to insulin, and they found it to be substantially higher with cinnamon; again the improvement was about the same regardless of when the cinnamon was given within that 12-hour window.

Better Stats, but Questionable Explanation

So now we have three out of four studies, not two out of three, demonstrating the value of cinnamon for improving glucose tolerance and insulin sensitivity in humans. Based on the numbers alone, that improves our confidence level (from 67% to 75%) that the effect is real and not an artifact—especially when we recall that these studies tend to confirm the results of prior laboratory and animal studies.

Naturally, though, we would like to know why that Dutch study showed no effect while the other three did. The British authors offered some speculations on this, but their primary argument, regarding dosage amounts, was based on a blatantly false characterization of the Pakistani study and was thus spurious.* Their secondary argument, however, was plausible, being based on differences in certain characteristics—diet, exercise, and medications—of the various patient groups involved. These represent factors that, in their words, “can markedly influence glycaemic control and insulin sensitivity.” Unfortunately, they gave no specifics regarding the differences in these factors in the four studies.

*They stated that the Pakistani study “found little effect of 1 g/day, yet marked effects at 3 and 6 g/day.” In fact, however, all three cinnamon doses had a strong effect on blood glucose levels, and on blood lipid levels as well. Furthermore, the 1-g/day dose produced the most sustained response of the three.

The Importance of Diet and Exercise

Based on much medical research, one would expect a healthy diet—well balanced, calorically appropriate, and low glycemic index—along with regular exercise, to maintain or improve glycemic control and insulin sensitivity. By the same token, one would expect a poor diet (such as the typical Western diet) and lack of exercise to degrade them. As for medications, one would have to know which ones they were to be able to predict an effect.

But in well-designed studies, the effects of factors such as these are largely eliminated in the first place, by excluding individuals whose health circumstances make them unsuitable and by using statistical methods to correct for the variations in the extraneous factors, thus “normalizing” the data so that the factor under investigation can stand out and be seen clearly.

That, at least, is the ideal—but knowing how close one came to achieving it can be extremely difficult, and the possibility of skewed results owing to some unseen factor hangs like a cloud over virtually every clinical trial.

Taking Cinnamon Is Patriotic

Which brings us back to the analogy between medicine and economics, both of which are at the mercy of irreproducible circumstances. No two tax cuts can ever occur under the same conditions, so their results will never be the same—they’re likely to be similar, but there is no guarantee. Similarly, we should not be surprised that, of four different clinical trials with cinnamon, only one was a dud, whereas three yielded positive results that were similar (but not, of course, the same). In both economics and medicine, three out of four isn’t bad.

Everyone loves tax cuts, right? They’re certainly good for our individual financial health, and they’re generally good for the economy as well. And who doesn’t love cinnamon? If it can improve our health as individuals, it can also improve our health as a society—which is good for the economy. So taking cinnamon is patriotic! Go for it!


  1. Khan A, Safdar M, Ali Khan MM, Khattak KN, Anderson RA. Cinnamon improves glucose and lipids of people with type 2 diabetes. Diabetes Care 2003;26(12):3215-8.
  2. Mang B, Wolters M, Schmitt B, Kelb K, Lichtinghagen R, Stichtenoth DO, Hahn A. Effects of a cinnamon extract on plasma glucose, HbA1c, and serum lipids in diabetes mellitus type 2. Eur J Clin Invest 2006;36(5): 340-4.
  3. Vanschoonbeek K, Thomassen BJ, Senden JM, Wodzig WK, van Loon LJ. Cinnamon supplementation does not improve glycemic control in postmenopausal type 2 diabetes patients. J Nutr 2006;136(4):977-80.
  4. Solomon TPJ, Blannin AK. Effects of short-term cinnamon ingestion on in vivo glucose tolerance. Diabetes Obes Metab 2007;9(6):895-901.


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