Even Michelin starred chefs have a bit of renegade smuggler in them; for years, chefs from top US restaurants, like New York City’s Le Bernard, have been buying tonka beans to spice up their food despite the beans having been banned by the Food and Drug Administration. When studies showed that high levels of coumarin, the flavour compound in tonka beans, were leading to hepatotoxicity in dogs and rats (chemical driven liver damage), the FDA chose to outright ban the beans from commercial use. But tonka beans remain a well-loved and occasionally used ingredient in both Canada and Europe; Montreal’s BouillionBilk currently uses it in a chocolate pastry dessert, and the famous Canadian Chef Marc Lepine and owner of Ottawa’s Atelier restaurant, has used it experimentally for years. So what exactly are these mysterious beans and why do American chefs need to use illegal means to obtain them?
The “dipteryx odorata,” or “cumaru” tree, native to South America, bares the small prune-like tonka seeds. Renowned for their indescribable smell, the bean shavings are used commonly in sweet dishes as a flavor additive like vanilla. Bean extracts are also ingredients in many perfumes, cosmetics, detergents and even tobacco and e-cigarettes. The French use the expression "fièvre tonka”, a pun on the French word “onfève” for “bean”, to describe the intense passion that chef’s and perfumer’s alike share for this sweet flavor.
Coumarin, or is 1,2-benzopyrone, occurs naturally in tonka beans and cinnamon, but can also be found in trace amounts in bison grass, green tea, carrots, and even some beers. Poisoning by coumarin is extremely rare and has only occurred in clinical settings, where high doses of the chemical were medically administered as treatments for lymphedema and some cancers. Recently researchers found that subgroups of humans might be more susceptible to the hepatotoxic effects of the chemical, but the mechanism for why this might be is unknown. Even with an added risk, heavy consumers of the compound barely reach levels of threatening exposure. Accordingly, the FDA ban on this substance has been highly criticized since it is very unlikely that anyone could be exposed to enough coumarin from tonka beans to cause liver damage. It has been estimated that every day we consume about 0.06mg/kg of the substance daily through our diet and cosmetics. This falls safely under the 2004 tolerable daily food intake (TDI) set by the European Food Safety Authority (EFSA) at 0.1mg/kg daily. For a fully grown adult to research this threshold, they would need to consume about 2400 plates of tonka bean flavoured desserts, in which case liver damage would probably not be their major concern.
In Canada, directly adding coumarin to food is illegal, but consuming it through other spices, like tonka beans, is not. One of the most common ways that coumarin makes its way into our diets is actually through cinnamon, an extremely popular spice, second only to black pepper. There are two kinds of cinnamon, Ceylon (most from Sri Lanka known as “true cinnamon”), and cassia (the cinnamon imposter from China and Indonesia). It is nearly impossible for consumers to tell the difference between the powered substances, save geographic information on the package. Both contain coumarin, though the fake stuff has greater concentrations than the Sri Lankan variety (1% in cassia and only about 0.004% in ceylon). Consuming incredible amounts of cassia cinnamon might increase the risk of coumarin induced hepatotoxicity, but even to reach the recommended TDI of coumarin in cassia, one would need to consume 2g of cinnamon daily for several weeks. That’s about 24 standard cinnamon cookies every day for at least 3 weeks! In a 2012/2013 survey, Health Canada found that throughout the country, concentrations of coumarin in cinnamon products were not high enough to be considered threatening to human health.
Thus as long as you’re not undergoing daily “cinnamon challenges”, you’re quite safe to enjoy your coumarin flavored special desserts, just not 2400 servings on any given day.