Safrole

The rat study used a dose of 5 mg per kilogram of body weight per day administered for the lifetime of the animals. A traditional cup of boiled sassafras root tea contains approximately 3 mg of safrole. The FDA's 1960 ban was based on a single 1958 rodent study in which rats given high doses of pure safrole developed liver tumors. Properly fermented home root beer produces safrole levels below the 10 ppm commercial legal threshold. Safrole has not been tested for safety in pregnant populations. A 150-lb human would need to drink roughly 33 cups of strong sassafras tea daily for decades to approach the rat toxicity threshold. Safrole is a naturally occurring phenylpropanoid found not only in sassafras but also in nutmeg, basil, cinnamon bark, and black pepper.