What are the safety concerns about long‑term cinnamon supplementation (coumarin exposure) and how do Ceylon and cassia cinnamon differ?
Executive summary
Long‑term cinnamon supplementation raises safety questions because cassia cinnamon commonly contains high levels of the naturally occurring compound coumarin, which regulatory bodies link to liver toxicity at sustained doses above a tolerable daily intake (TDI) [1] [2]. True (Ceylon) cinnamon typically contains only trace amounts of coumarin and is therefore the safer choice for people who consume cinnamon daily or take cinnamon supplements [1] [3].
1. What coumarin is and how regulators treat it
Coumarin is a naturally occurring fragrant compound found in several plants including many cassia cinnamons, and health authorities established a TDI of 0.1 mg per kg body weight (EFSA/BfR) because animal studies linked high coumarin exposures with liver damage and tumor formation in rodents [1] [3] [2].
2. Evidence linking long‑term coumarin exposure to harm
Toxicology and market surveys have shown that heavy, chronic intake of cassia—especially via supplements, daily large spoonsful, or cinnamon‑rich bakery products—can push consumers above the TDI and therefore into a range where long‑term hepatotoxic risk becomes plausible; regulatory assessments and food surveys have repeatedly warned that frequent, high‑dose cassia consumption is the main route to risky coumarin exposure [3] [2] [1].
3. How Ceylon and cassia cinnamon differ in coumarin content
Measured coumarin levels vary enormously by species: surveys and publications report cassia powders with hundreds to thousands of mg/kg of coumarin (ranges cited from several hundred up to >7,000 mg/kg in some samples), while Ceylon cinnamon samples consistently show only trace levels (single‑digit to low hundreds of ppb in most surveys), meaning cassia can contain orders of magnitude more coumarin than Ceylon [4] [1] [3].
4. Practical implications for supplementation and daily use
Because an average teaspoon of cassia powder can contain enough coumarin to approach or exceed the EFSA/BfR limit for many adults and especially for children or small adults, anyone taking cinnamon as a daily supplement or consuming multiple teaspoons a day should prefer verified Ceylon cinnamon or limit cassia intake; regulators and national authorities explicitly advise using Ceylon for frequent home use and caution about cinnamon‑containing supplements that may be cassia‑based [5] [6] [2].
5. Other safety variables and counterarguments
The story is not only coumarin: supply chain contamination (for example lead or other adulterants) and product testing quality matter, so a low‑coumarin Ceylon product could still be unsafe if poorly sourced, while a well‑tested cassia with low contaminants and modest dosing might be acceptable for short‑term use [7]; additionally, some risk assessments note that transient intakes modestly above the TDI for a week or two are unlikely to be harmful, and human data on chronic low‑dose outcomes are limited compared with animal models [4] [3].
6. Uncertainties, hidden agendas and what the sources emphasize
Industry and specialty sellers often emphasize Ceylon as “safer” (and charge a premium), which aligns with the science on coumarin but can bias messaging toward absolute safety claims; public health agencies focus on population exposure and point to cassia as the primary concern, while consumer blogs and vendors may underplay supply‑chain heavy metal risks or lack of third‑party testing [8] [7] [9].
7. Bottom line for long‑term supplementation
Long‑term cinnamon supplementation that relies on cassia risks chronic coumarin exposure associated with potential liver toxicity and should be avoided or limited to doses below regulatory guidance; for daily users, choosing true Ceylon cinnamon (or supplements explicitly tested and labeled for low coumarin) substantially reduces that specific risk, while broader safety depends on product testing and individual health status—particularly preexisting liver disease and small body size [1] [6] [7].