Image Source: / Gualberto107

Image Source: / Gualberto107

Cinnamon, Coumarins and Breast Cancer

I have recently been asked by a few people whether or not cinnamon promotes cancer or caused problems for those with breast cancer.  I had never heard of that, in fact, in my studies I have found quite the opposite – that cinnamon has anti-cancer properties.

The people asking me had apparently been reading something on the Internet which indicated there was a problem with cinnamon.  “Time to go into research mode”, I thought.

First of all, there are a few different kinds of cinnamon:

Cassia cinnamon (Cinnamomum aromaticum)
Ceylon cinnamon (Cinnamomum zeylanicum)
Indonesian cinnamon (Cinnamomum burmanni)
Vietnamese or Saigon cinnamon (Cinnamomum loureiroi)
Mexican cinnamon (Cinnamomum verum)

Most of the articles I discovered in my Google search had one thing in common – the problem with cinnamon appeared to be associated with the levels of a plant chemical known as coumarin.  Coumarin (benzo-a-pyrone) is a natural substance found in many plants. It is the natural chemical upon which Coumadin, a well-known drug used for its anti-coagulant properties, was based back in 1858.

I discovered three things:

1. Coumarin has the potential to damage the liver in high doses.
2. Not all of the above-listed types of cinnamon contain high levels of coumarin.
3. There existed plenty of research stating cinnamon does have anti-cancer properties.

The Coumarin/Cinnamon Studies

There were plenty of studies about coumarin, and I could not possibly list them all here. Here are but a few that discussed the coumarin levels in cinnamon.

A 2013 study indicated that Cinnamomum verum bark contained only traces of coumarin, whereas barks from three other cassia species, especially C. loureiroi and C. burmannii, contained substantial amounts of coumarin. 1

A 2012 study from the Czech Republic analyzed 60 cinnamon samples and discovered high levels of coumarins in C. aromaticum, but C. zeylanicum was coumarin free. 2

Oddly, one 2010 research study indicated that levels of coumarins varied widely, even within the same tree. 3

Other than the disparities in those studies mentioned above, most of the studies I found agreed that of the cinnamon species, Ceylon cinnamon (C. zeylanicum) had the least amount of coumarins, while Cassia cinnamon tended to contain higher levels of coumarins. And it’s the Cassia cinnamon that is most commonly sold in the grocery stores, at least in America, Australia and Great Britain.

And of course there were a couple of studies that discussed the toxicity of coumarin on the livers of rodents.  But interestingly, most of the more recent studies I located indicated that coumarins had protective effects.  One 2011 study indicated coumarins played an important role for the protection of liver toxicity in rats. 4

Coumarins as Anti-Cancer Agents

Here’s where it gets really interesting. I did find some studies discussing how coumarins were being researched for their anti-cancer properties.

In one 2015 study, 27 coumarin derivatives were synthesized and found to be toxic to estrogen/progesterone receptor positive breast cancer cells (among a few other cancer cell lines). 5

I also found four separate studies which indicated coumarins were effective against lung cancer cells, the most interesting of which indicated coumarins inhibited lung carcinoma cell growth by inducing cell cycle arrest. 6

One 2007 study indicated one particular form of coumarin induced apoptosis (programmed cell death, something absent from cancer cells) in human lung adenocarcinoma cells. 7

Cinnamon And Estrogen

To confound matters further, the Memorial Sloan Kettering Cancer Center website contains this warning: “Do not take cinnamon if you have hormone-sensitive cancer (cinnamon was found to have both estrogenic and antiestrogenic activities).”  The article did not indicate which research study it was relying upon for that information, however, at the bottom of the page, I was able to locate just one study that showed Cassia cinnamon exerted anti-estrogenic effects.

So Is Cinnamon Safe? Is It Helpful For Breast Cancer?

Let’s look at the situation carefully.  Here is what we do know:

  • Cinnamon contains several carotenoids and proanthocyanidins, phytochemicals that have cancer preventing benefits
  • Cinnamon is a stupendously powerful antioxidant (and we know antioxidants help fight cancer)
  • Cinnamon contains cinnamaldehyde, a natural anti-inflammatory chemical (and we know that cancer is an inflammatory process)
  • Cinnamon helps to lower blood sugar and reduces insulin resistance (and we know that insulin resistance and high blood sugar can lead to type 2 diabetes and metabolic syndrome, both of which are linked to breast cancer)
  • Studies on cinnamic acid, another phytochemical within cinnamon, indicate it has potent anti-cancer effects. It fights cell proliferation, angiogenesis, and is anti-tumoral. 10
  • An extract of C. zeylanicum (Ceylon cinnamon) has been shown to inhibit vascular endothelial growth factor (VEGF), which is crucial to the process of angiogenesis, the formation of new blood vessels to feed a tumor. 11
  • A phytochemical known as 2-Hydroxycinnamaldehyde, derived from C. aromaticum (Cassia cinnamon), showed promise in inhibiting epithelial-mesenchymal transition (EMT), which plays a pivotal role in the spread (metastasis) of breast cancer cells. 12

So I would say, yes, cinnamon definitely shows great promise for breast cancer. But because of the coumarins within some varieties of cinnamon you need to be cautious about which type you have. If you aren’t sure which kind you have, you should be cautious about how often you have it.

My best advice:

1. Only buy Ceylon cinnamon (C. zeylanicum) as it appears to have the lowest amounts of coumarins;
2. Don’t eat cinnamon every single day but do use it in your cooking – remember that moderation is always the best idea;
3. Don’t take Cassia cinnamon if you are on blood-thinners;
4. Don’t mix Cassia cinnamon with pharmaceutical drugs, this does appear to cause problems for the liver.


1. Cassia Cinnamon As A Source Of Coumarin In Cinnamon-Flavored Food And Food Supplements In The United States –

2. Assessment of coumarin levels in ground cinnamon available in the Czech retail market —

3. Quantification of Flavoring Constituents in Cinnamon: High Variation of Coumarin in Cassia Bark from the German Retail Market and in Authentic Samples from Indonesia –

4. Protective effects of coumarin and coumarin derivatives against carbon tetrachloride-induced acute hepatotoxicity in rats —

5. Structure-activity relationship studies of 4-methylcoumarin derivatives as anticancer agents –

6. Apoptosis and cell cycle disturbances induced by coumarin and 7-hydroxycoumarin on human lung carcinoma cell lines –

7. 7,8-Dihydroxy-4-methylcoumarin induces apoptosis of human lung adenocarcinoma cells by ROS-independent mitochondrial pathway through partial inhibition of ERK/MAPK signaling –

8. Screening of estrogenic and antiestrogenic activities from medicinal plants –

9. Cinnamon intake lowers fasting blood glucose: meta-analysis –

10. Anticancer Agents Derived from Natural Cinnamic Acids –

11. Novel angiogenesis inhibitory activity in cinnamon extract blocks VEGFR2 kinase and downstream signaling –

12. 2-Hydroxycinnamaldehyde inhibits the epithelial-mesenchymal transition in breast cancer cells –

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