Wild yam extract (root). The roots of Dioscorea species are true yams and are not related to the sweet potato, which is incorrectly called a yam in the U.S. Dioscorea tubers typically contain 80-90% starch, are low in protein, and contain appreciable amounts of vitamin C and calcium 1. Dioscorea species are also a rich source of the saponin, diosgenin 2. The roots are commonly consumed in Africa, the tropics, Central America, and the Caribbean. In West Africa, they may comprise 0.3-49% of total daily caloric intake 1. An extract of D. villosa has been subjected to extensive safety testing and did not cause adverse effects when consumed in large amounts by adults 3.