GUMBO FILE unlike sassafras roots or bark which are weakly carcinogenic, Gumbo filé powders are made from the dried and ground leaves of the North American sassafras tree (Sassafras albidum). These leaves and not considered carcinogenic. It does not contain safrole, banned by the FDA due to its carcinogenic properties. The Choctaw Indians chewed sassafras roots to bring down fevers. Gumbo filé is sprinkled sparingly over gumbo to thicken it and give it an earthy flavor.