Coumarin is a natural chemical compound known for its sweet, vanilla-like aroma. While it is widely found throughout the plant kingdom, it appears in significant concentrations in certain plants used for food and drink production. For tea drinkers, the primary concern revolves around cinnamon-based teas, although coumarin can also be found in other herbal infusions and even some green teas. Although moderate consumption is generally considered safe for most people, an excessive, long-term intake can pose a risk of liver toxicity, particularly for sensitive individuals.
Cassia Cinnamon Tea: The Primary Source of Coumarin
Cassia cinnamon (Cinnamomum cassia), often simply labeled as "cinnamon" in North America and many other parts of the world, is the leading source of coumarin in teas and other food products. It is the most common and least expensive variety, prized for its strong, pungent flavor. Teas that contain a high proportion of cassia cinnamon, such as chai tea mixes and many flavored black or herbal cinnamon teas, will therefore contain a corresponding amount of coumarin. The coumarin concentration in cassia can be up to 1%, compared to trace amounts in its more expensive counterpart, Ceylon cinnamon. Regular, heavy consumption of cassia-based products, including teas, is the main way individuals might approach or exceed the tolerable daily intake for coumarin.
The Critical Distinction: Cassia vs. Ceylon
For those concerned about coumarin intake, understanding the difference between cassia and Ceylon is paramount. Ceylon cinnamon (Cinnamomum verum), or "true cinnamon," comes primarily from Sri Lanka and contains only negligible amounts of coumarin. It is characterized by its milder, sweeter, and more delicate flavor profile. In stick form, Ceylon cinnamon is distinguished by its light, papery, multi-layered texture, while cassia sticks are thicker and form a tight single roll. However, when both are ground into powder, visual identification becomes nearly impossible. The only reliable way for consumers to ensure they are getting low-coumarin cinnamon is to check the label for "Ceylon cinnamon" or "true cinnamon". Some producers will specify the type, but many simply list "cinnamon," which often implies the high-coumarin cassia variety. The health agencies of several countries have recommended switching to Ceylon for individuals who consume large amounts of cinnamon regularly.
Green Teas and Coumarin
While less concentrated than in cassia cinnamon, coumarin is also present in green teas. Its presence is linked to the tea's sweet, herbaceous aroma, particularly in certain Japanese cultivars. A study on Japanese green tea found that specific cultivars, such as "Shizu-7132" and "Koushun," contained higher coumarin levels (0.67-0.88 μg/g) than common green tea products (below 0.2 μg/g). The coumarin content in green tea is also influenced by processing methods, such as steaming time and drying temperature. Although the concentrations are low and unlikely to pose a risk in typical quantities, it's an interesting aspect of the tea's chemistry.
Herbal Teas with Naturally Occurring Coumarins
Beyond cinnamon, several popular herbal teas contain coumarin or related compounds. Chamomile tea, for example, is known to contain the coumarins herniarin and umbelliferone, though they make up only a small fraction of the flower's total constituents. Additionally, sweet clover tea (Melilotus officinalis) is a well-known source of coumarin. Other plants used in herbal medicine and infusions, such as tonka beans and sweet woodruff, also contain coumarins.
Comparison of Coumarin in Common Tea Ingredients
| Ingredient | Coumarin Content | Flavor Profile | Common Tea Use |
|---|---|---|---|
| Cassia Cinnamon | High (up to 1%) | Strong, pungent, spicy | Chai tea, flavored herbal tea |
| Ceylon Cinnamon | Very Low (trace) | Mild, delicate, slightly sweet | Gourmet tea blends, sensitive recipes |
| Chamomile | Low (herniarin, umbelliferone) | Floral, apple-like | Calming herbal tea |
| Japanese Green Tea | Low (higher in some cultivars) | Sweet, herbaceous, umami | Unflavored green tea |
| Sweet Clover | Moderate to High | Hay-like, sweet | Specific herbal infusions |
Health Risks of Coumarin and Safe Intake
While coumarin can be toxic in large doses, typical exposure from food and beverages, including teas, is generally not a concern. The main risk is liver toxicity for sensitive individuals from chronic, excessive intake. The European Food Safety Authority (EFSA) and other health bodies have established a Tolerable Daily Intake (TDI) of 0.1 mg of coumarin per kilogram of body weight. For a 60 kg adult, this means an intake of no more than 6 mg per day on average over a long period. Health agencies have issued warnings regarding high consumption of cassia cinnamon because it is the most likely dietary source to cause an exceedance of the TDI.
Conclusion: Making Informed Tea Choices
Coumarin is a component of many natural plants, including several found in popular teas. While most standard green and herbal teas contain low levels, teas flavored with cassia cinnamon are a significant dietary source. By being aware of which teas contain coumarin and understanding the difference between cassia and Ceylon cinnamon, you can make more informed choices about your consumption. Moderation is key for teas containing high-coumarin ingredients. For individuals who regularly consume large amounts of cinnamon tea or have liver sensitivities, choosing certified Ceylon cinnamon is the safest alternative. As always, for persistent health concerns, it's best to consult a healthcare professional. For more details on the toxicology of coumarin, a comprehensive review is available from a National Institutes of Health (NIH) resource.
