Over the past 15 years, researchers have reported that cinnamon can amplify the effects of insulin and help cells respond more appropriately (Khan et al, Diabetes Care, Dec. 2003; Mang et al, European Journal of Clinical Investigation, May 2006; Kirkham et al, Diabetes, Obesity & Metabolism, Dec. 2009; Davis & Yokoyama, Journal of Medicinal Food, Sep. 2011; Anderson et al, Journal of Traditional and Complementary Medicine, April 18, 2015). But which cinnamon lowers blood sugar best? That is a controversial topic.

Lower Blood Sugar vs. Liver Safety:

Q. You’ve written about cinnamon as a supplement that could help control blood sugar levels. I understood you to say that Cinnamomum cassia has more coumarin than Cinnamomum verum. Coumarin should be avoided because it might harm the liver.

The cinnamon I purchased says Cinnamomum burmannii (bark) on the label. Do you know how much coumarin this type of cinnamon has?

Coumarin in Various Types of Cinnamon:

A. Cinnamomum burmannii is native to Indonesia. It contains many of the same compounds that provide the familiar cinnamon flavor from cassia cinnamon (Cinnamomum cassia) or Ceylon cinnamon (Cinnamomum verum). C. burmannii has anti-inflammatory activity and can help regulate blood sugar after a meal (Al-Dhubiab, Pharmacognosy Review, Jul-Dec. 2012).

You are right that coumarin has the potential to damage the liver (Iwata et al, Frontiers in Pharmacology, June 20, 2016). Relatively high levels are found in cassia cinnamon and also in C. burmannii. In fact, both Indonesian cinnamon (C. burmannii) and Saigon cinnamon (C. loureiroi) contain even more coumarin than cassia cinnamon (Wang et al, Journal of Agricultural and Food Chemistry, May 8, 2013). C. burmannii seems to be one of the most commonly used sources of cinnamon flavoring in foods sold in the US.

Avoiding Excess Coumarin:

Since coumarin is not water soluble, we suggest you make tea or another type of water extract with your C. burmannii. This should provide you with the benefits and minimize the risk of harmful liver effects. If you have the opportunity to use Ceylon cinnamon or Taiwanese C. osmophloeum twigs or leaves, you would be getting natural products with little if any coumarin (Yeh et al, Journal of Agricultural and Food Chemistry, Feb. 19, 2014).

Which Cinnamon Lowers Blood Sugar?

In many research reports, the investigators do not specify which type of cinnamon they used in their study (Costello et al, Journal of the Academy of Nutrition and Dietetics, Nov. 2016). Consequently, we have some difficulty determining which cinnamon lowers blood sugar most effectively. The first studies were conducted using cassia cinnamon. Soon thereafter, scientists began to examine C. verum (aka C. zeylanicum) to see if it can moderate blood sugar and insulin spikes after meals. Although initial results were discouraging (Wickenberg et al, British Journal of Nutrition, June 2012), research in rats and a handful of human volunteers suggests that C. verum may also be useful for blood sugar control (IM et al, Food & Function, Sep. 2014).

Reducing Coumarin While Lowering Blood Sugar:

Q. I was recently diagnosed with pre-diabetes. From reading previous People’s Pharmacy columns, I was aware that cassia cinnamon can be toxic unless put in a paper filter with coffee grounds. I have been mixing one teaspoon of cinnamon in my coffee grounds before brewing my coffee every morning.

In a recent column, a reader wrote that he wound up in the emergency room after consuming the same amount of cinnamon on a daily basis that I have been taking. Is it no longer considered safe to put cinnamon in coffee as I have been doing? I love the taste of cinnamon and would hate to have to take it in capsule form.

Avoiding Coumarin in Cassia Cinnamon:

A. The reader who developed liver damage from taking cinnamon didn’t say how he took it. That experience underscores the potential toxicity of coumarin in plain ground cinnamon.

Coumarin is a compound that is found in the same tree bark used to make cassia cinnamon. The compound can be toxic to the liver, and some years ago, the German government issued a warning that German citizens should avoid eating too many cinnamon star cookies at Christmastime. As Grinch-like as that seemed, the agency was attempting to protect the public health.

Because the amount of coumarin varies considerably depending on the source of cassia cinnamon, you can’t know without specialized testing how scary your supermarket cinnamon may be. The technology used is high-performance thin layer chromatography-bioautography-mass spectrometry (HPTLC-MS) and it demonstrates the extremely wide range of coumarin in cinnamon-containing foods (Kruger, Winheim & Morlock, Food Chemistry, Jan. 15, 2018).

You are following the best practice for protecting yourself from coumarin by using the water extract (in the form of your coffee) and leaving the rest of the powdered spice behind. Coumarin is not water-soluble, while the compounds that reduce blood sugar are. Consequently, consuming the “aqueous extract” as you do when you put cinnamon in your paper coffee filter is a good way to lower blood sugar safely.

Ellie has a suggestion on how to do this:

“Our family has been adding cinnamon to our pot of coffee for years. We put a mixture of cinnamon and cacao powder (no sugar included) into the coffee filter. Then, we put another filter on top of the cinnamon-cacao filter in which we put the coffee. It makes a slight chocolate-cinnamon flavor to the coffee to go with added health benefits. Yumm!”

What About Ceylon Cinnamon?

Ceylon cinnamon, although it is pricier, would be even safer than C. burmannii, as C. verum contains little or no coumarin (Beejmohan et al, BMC Complementary and Alternative Medicine, Sep. 23, 2014). Research shows that it reduces post-meal blood sugar by about 20 percent compared to placebo. A review found that Ceylon cinnamon could be helpful in reducing metabolic syndrome, a disorder associated with a large waistline, high cholesterol, hypertension and elevated blood sugar (Mollazadeh & Hosseinzadeh, Iranian Journal of Basic Medical Sciences, Dec. 2016).

What Is the Difference Between Cassia and Ceylon Cinnamon?

Ceylon cinnamon (Cinnamomum verum) and cassia cinnamon (Cinnamomum cassia) are two different species within the same genus. In both cases, the spice is made from the tree bark. Other species of tree that are sometimes used to produce cinnamon include C. loureiroi, termed Vietnamese or Saigon cinnamon, C. burmannii, sometimes termed korintje cinnamon, and C. citriodorum, or Malabar cinnamon. Cassia cinnamon and Indonesian cinnamon are the types most often found as ground cinnamon spice on North American supermarket shelves.

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