"Before the law, refined coumarin was commonly added to commercial foods like cream soda, and used in synthetic vanillin. Extreme concentrations caused liver problems in rats (how unappetizing), and a rather overreaching ban on even natural sources of the compound was put in place. Coumarin has since been found to occur naturally in cinnamon, lavender, licorice, and a host of other commonly eaten plants—all of which would seem to be illegal under the regulation. Coumarin also accounts for the particular smell of fresh-cut grass and of fresh-dried hay (both in Alinea's grass-gas scent-pillows, and on your front lawn).
The fear of coumarin in the U.S. stems from the oft-repeated saw that it is a blood thinner. It's not. Coumadin® is the blood thinner trademarked by Bristol-Meyers Squibb. To make matters more confusing, Coumadin is made, in part, by changing the chemical structure of coumarin. Doctors who spoke with me (and who were terrified of being quoted) said there they're aware of no anti-coagulant effect from naturally occurring coumarin in general, or tonka beans in particular. In nature, only certain rare decomposition fungi can convert coumarin to the anti-coagulant molecule. Cows grazing on (pounds of) such rotting sweet clover led to the discovery of the Coumadin drug.
Humans would need to eat an unreasonably bovine amount of tonka bean to fall ill. The shavings of a single bean is enough for 80 plates. At least 30 entire tonka beans (250 servings, or 1 gram of coumarin total) would need to be eaten to approach levels reported as toxic—about the same volume at which nutmeg and other everyday spices are toxic."
https://www.theatlantic.com/health/archive/2010/11/the-tonka-bean-an-ingredient-so-good-it-has-to-be-illegal/65616/
The fear of coumarin in the U.S. stems from the oft-repeated saw that it is a blood thinner. It's not. Coumadin® is the blood thinner trademarked by Bristol-Meyers Squibb. To make matters more confusing, Coumadin is made, in part, by changing the chemical structure of coumarin. Doctors who spoke with me (and who were terrified of being quoted) said there they're aware of no anti-coagulant effect from naturally occurring coumarin in general, or tonka beans in particular. In nature, only certain rare decomposition fungi can convert coumarin to the anti-coagulant molecule. Cows grazing on (pounds of) such rotting sweet clover led to the discovery of the Coumadin drug.
Humans would need to eat an unreasonably bovine amount of tonka bean to fall ill. The shavings of a single bean is enough for 80 plates. At least 30 entire tonka beans (250 servings, or 1 gram of coumarin total) would need to be eaten to approach levels reported as toxic—about the same volume at which nutmeg and other everyday spices are toxic."
https://www.theatlantic.com/health/archive/2010/11/the-tonka-bean-an-ingredient-so-good-it-has-to-be-illegal/65616/