Cinnamon's Impact on Blood Sugar

One way or another, we all know cinnamon. And the spice (actually, tree bark) enjoys a well-known reputation for health based on popular herbal lore.

By Mark Anthony, Ph.D.

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Modern science has found cinnamon to be more and more intriguingly deserving of a healthy reputation. Over the years, studies have gone a long way to prove cinnamon's connection to such benefits as antimicrobial action and lower LDL cholesterol.

What's more recent is science connecting cinnamon to the stabilization of blood sugar for many individuals. That's the conclusion coming from an article published at the beginning of the year in The American Journal of Clinical Nutrition.

Previous studies, including a well-reported in 2003 in Diabetes Care, had demonstrated cinnamon lowers fasting serum glucose, triglycerides (blood fats), LDL and total cholesterol in patients with type-2 diabetes. The 2007 study, conducted at the University of Lund, Sweden, was different in that it focused on healthy subjects.

Fourteen healthy volunteers were given rice pudding, either plain or spiked with 6g of cinnamon, in a crossover study (a clinical trial in which the study subjects receive each treatment in a random order, each subject serving as his or her own control.) The aim of the study was to measure the after-meal blood sugar -- the rate at which the stomach emptied into the small intestines (gastric emptying) and how both affected satiety. The results were interesting.

The addition of cinnamon reduced both after-meal blood sugar and gastric emptying. Slowing gastric emptying is a proven way to lower after-meal blood glucose levels. (That's how fats work and why fatty foods generally have a low glycemic index   a measure of after-meal blood glucose compared to a standard.) As a side note, by slowing gastric emptying, fats decrease the delivery of dietary carbohydrates to the small intestines, a phenomenon that undermines the credibility of glycemic index as the determinant of carbohydrate value.

But here's the spicy kicker: The effect of cinnamon on blood sugar in this study was greater than could be accounted for by the slowdown of the gut. There must be something else about cinnamon at work.

Eating carbohydrates stimulates the production of insulin from the pancreas. At the cell surface, special insulin receptors bind the insulin and increase the uptake of glucose into the cell. Previous studies showed cinnamon can make the insulin receptor on the cell surface work better, which means more glucose is pulled out of the blood after a meal containing carbohydrate. It's the non-responsiveness of cells to insulin that is believed to be at the heart of type 2 diabetes.

Surprisingly, the negative impact on blood glucose and the slowing of gastric emptying did little to affect satiety. That may have been due to the small number of subjects. Subjects reported slightly greater satiety at each time point of data collection, but not enough to add up to statistical significance.

So, what does all this mean? We have a traditional spice that nearly everyone loves that can lower cholesterol and blood fats, and possibly help normalize blood sugar.

But before processors start to add cinnamon to everything and brand it as a health food, there's still a matter of possible potential complications with the spice itself.

In the Diabetes Care article, researchers used Cinnamomum cassia or Cinnamomum aromaticum, aka "Chinese cinnamon" (cassia for short). Cassia is a close relative of cinnamon, but it lacks the delicate flavor of Cinnamomum verum, Ceylon cinnamon, or "true cinnamon." What's the difference? Cassia, which accounts for most of the cinnamon found in processed foods, contains relatively large amounts of coumarin, a naturally occurring compound that can act as a blood thinner (not related to the drug Coumadin, an anticoagulant). In high concentrations can damage the liver. True cinnamon contains very small amounts of coumarin.

How can you tell if you have true cinnamon? When the spice is powdered, it's nearly impossible for consumers to distinguish between the two varieties. And packages generally do not declare the origin of the cinnamon. The sticks are different. Cassia cinnamon is a relatively thick layer of the bark rolled into a stick. Ceylon cinnamon stick is a roll of several thin layers of bark, giving the appearance of a compact cross section.

There are several questions left unanswered. Will these findings hold up in larger studies, and with different varieties of cinnamon? Is coumarin a problem if consumed as part of the cinnamon? Studies indicating liver toxicity used isolated coumarin, not cinnamon. For now, it seems if using cinnamon as an ingredient for health, it's wise to be moderate.

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