In my previous article on cinnamon and cassia oil, I explored the benefits of this sweet spice in all its yummy varieties. These included cinnamon’s favorable effects on blood sugar, cardiovascular markers, and immune health. I also began my discussion on some of the cautions of using Cassia cinnamon, specifically in relation to its coumarin content.

In this post you will learn:

– why we may want to be mindful, though not frightened, of coumarin

– more details regarding the anticoagulant (blood-thinning) and liver precautions of Cinnamomum cassia

– staying within safe doses of cassia and who may want to avoid this spice variety altogether

In the final article, I will sum up what was learned about cinnamon and cassia and provide additional uses and indications for the spice and oil.

In the end, I hope you won’t fully shun cassia, but enjoy its wellness effects without going heavy handed with the essential oil or spice bottle.

What are Coumarins & Why Are We So Cautious with Them?

Coumarins are natural, aromatic compounds that are widespread throughout the plant kingdom. They are classified as secondary metabolites which protect the plant from infestations and play a role in modulating their physiology. They act as antioxidants, enzyme inhibitors, and precursors to toxic substances for defense. (source)

Coumarin and its derivatives possess various biological properties that depend on their chemical structure. For example, they have been used in many pharmacological applications due to their antimicrobial, anti-inflammatory, anticoagulation, and many other actions. (source)

A variety of foods, spices, medicinal plants, and some essential oils contain coumarins. The most common exposure to them is through certain types of cinnamon, specifically cassia. (source)

This is Your Liver on Coumarin

Europe and the United States have regulations in place for coumarin intake and manufacturing. It is prohibited from being isolated and taken in pure form in both countries, as it has been purported to be toxic to the liver in high amounts. Notably, the original toxicity studies that determined the upper threshold of intake used rodents as test subjects. It has since been elucidated that humans elimination routes are likely to be more effective and more varied than in rats. (source, source, source)

According to a 2020 article, “Coumarins in Food and Methods of Their Determination:

EFSA’s Scientific Panel on Food Additives, Flavourings, Processing Aids and Materials in Contact with Food [30] were asked to review the toxicity of coumarin. The panel concluded that coumarin was not genotoxic in experimental animals and therefore a TDI (tolerable daily intake) could be derived. Established TDI, based on hepatotoxicity in a two-year dog study, was 0 – 0.1 mg coumarin/kg bw. Human data from the medicinal use of coumarin evaluated by the Federal Institute for Risk Assessment (Bundesinstitut für Risikobewertung) (BfR) [31] and identification of lowest daily dose capable of inducing liver toxicity [32] resulted in the same value for TDI as already established by EFSA (2004).

For those who tend to be more moderate in their spice usage, Natural Medicine Database echoes some of this concern, yet states that overall ingestion will probably not exceed safe doses and not cause long-term liver damage. (source, subscription required, bold emphasis mine):

There is some concern about the safety of ingesting large amounts of cassia cinnamon for extended durations due to its coumarin content. Coumarin can cause hepatotoxicity in animal models (15299). In humans, very high doses of coumarin from 50-7000 mg/day can result in hepatotoxicity that resolves when coumarin is discontinued (15302). In clinical trials, taking cassia cinnamon 360 mg to 12 grams daily for 3 months did not significantly increase aspartate transaminase (AST) or alanine transaminase (ALT) (21918,96280). However, in one case report, acute hepatitis with elevated AST and ALT occurred in a 73-year-old woman who started taking a cinnamon supplement (dose unknown) one week prior to admission. The cinnamon supplement was added on to high-dose rosuvastatin, which may have led to additive adverse hepatic effects. After discontinuing both products, the patient’s liver function returned to normal, and she was able to restart statin therapy without further complications (97249). In most cases, ingestion of cassia cinnamon won’t provide a high enough amount of coumarin to cause significant toxicity; however, in especially sensitive people, such as those with liver disease or taking potentially hepatotoxic agents, prolonged ingestion of large amounts of cassia cinnamon might exacerbate the condition.

Coumarin and Blood Thinning

Beyond liver health, another concern with coumarin is that it has blood thinning properties. Those on specific anticoagulant medications need to be cautious of this. There have been studies that demonstrate that those on coumarin anticoagulants tend to have a higher association with microbleeds, so it would be wise not to add to this effect. (To spin it another way, cassia could be considered for those who wish to use a natural blood thinner. This would need to be discussed with one’s doctor and monitored carefully.)

Should You Avoid Cassia Due to Its Cautions?

Does its potential liver harm and blood thinning aspects mean we should avoid Cassia cinnamon? It depends.

For those on certain blood thinners that are impacted by coumarin, it is important to monitor intake of this substance. In this scenario, it may be wise to switch your species of cassia to another cinnamon type.

When taken in moderate quantities, liver toxicity is not likely a concern; however, there are certain populations that need to be very cognizant of its dosage. For example, tolerable threshold limits can be exceeded easily if little ones are consuming several servings of cinnamon treats at once. Those who are regularly imbibing large amounts of tea along with combinations of other products, and those with liver issues, need to be cautious as well. (source, source) Finally, pregnant woman may wish to avoid cassia due to a link to neurological effects in those taking prescription coumarin. It is important to note that this is an association with synthetic coumarin, not a natural source.

Healthline states:

In fact, the Tolerable Daily Intake (TDI) of coumarin used to be 0.2 mg/lb (0.5 mg/kg) of body weight. It has now been reduced to 0.05 mg/lb (0.1 mg/kg) (source).

Cassia cinnamon, but not Ceylon, is a very rich source of coumarin.

Cassia contains approximately 1% coumarin, while Ceylon contains only 0.004%, or 250 times less. This is so low that it’s often undetectable. (source, source)

Exceeding the upper limit for coumarin is easily possible if you are consuming a lot of cassia cinnamon. In many cases, just 1-2 teaspoons could bring someone over the daily limit.

Therefore, if you regularly eat a lot of cinnamon or take a supplement that contains it, then it should be Ceylon and not cassia.

In the final article on Cassia, I will finish off with uses of cinnamon cassia and why, beyond its cautions, it should not be overlooked. I will also report on several studies on the essential oil.

Mental Health Resources

*If you are experiencing a mental health crisis and/or are suicidal, please seek professional mental health support:

  • The National Suicide Prevention Lifeline (U.S.) — Call 1-800-273-TALK (8255)
  • Crisis Text Line — Text HOME to 741741 to connect with a crisis counselor
  • Lifeline Crisis Chat — Chat online with a specialist who can provide emotional support, crisis intervention and suicide prevention services at


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Disclaimer: This material is for information purposes only and is not intended to diagnose, treat, or prescribe for any illness. You should check with your doctor regarding implementing any new strategies into your wellness regime. These statements have not been evaluated by the FDA. (Affiliation link.)

According to experts and the World Health Organization (WHO), there is no approved standard of care treatment, cure, or preventative for COVID-19. Supportive measures and containment are in full force as a result. Please see the CDC website and your state’s website for more information and updates. They also state when to contact your physician related to symptoms and travel history, exposures. Please read my more detailed article on this subject here.

This information is applicable ONLY for therapeutic quality essential oils. This information DOES NOT apply to essential oils that have not been tested for purity and standardized constituents. There is no quality control in the United States, and oils labeled as “100% pure” need only to contain 5% of the actual oil. The rest of the bottle can be filled with fillers and sometimes toxic ingredients that can irritate the skin. The studies are not based solely on a specific brand of an essential oil, unless stated. Please read the full study for more information.

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