Wild yam (also known as colic root, devil's bones, rheumatism root, or yuma) is a perennial vine found in open woods and moist thickets throughout much of the eastern United States. The plant has a woolly reddish-brown stem, which grows from 1 to 6 meters long, and broad, ovate leaves, which are 5 to 15 centimeters long and about three-fourths as wide. Wild yam flowers in June and July, bearing small, greenish-yellow blossoms, which eventually produce three-winged capsules containing winged seeds. The plant has a slender, knotty, matted, tuberous rootstock, which is used for health purposes.
While the medicinal use of other yam species dates back over 2,000 years, the "discovery" of wild yam was relatively recent. Dr. Bone, a Hessian mercenary and physician who settled in New Jersey after the American Revolution, is reported to have used wild yam root to treat "bilious colic" in the latter part of the 18th Century. Prior to that, the root was primarily used in poultices to treat wounds. Steroidal sapogenins found in several yam species have been used in the production of oral contraceptives and synthetic hormones (such as progesterone, corticosteroids, estrogens, androgens, and other sex hormones) since 1940. In recent years, wild yam root has become popular for treatment of menopausal symptoms, premenstrual syndrome (PMS), and abdominal cramps; however, there is little scientific evidence to support such use.
Wild yam contains steroidal sapogenins (most notably diosgenin) and alkaloids. Wild yam extracts are often standardized to provide consistent diosgenin levels.
Much of the popular use of wild yam is based on the erroneous belief that diosgenin can act as a precursor for DHEA, progesterone, and other steroid hormones. Pharmaceutical hormones are made from diosgenin through a chemical conversion process. This chemical synthesis does not occur in the body. There is no scientific evidence that the use of wild yam can influence hormonal levels or alleviate symptoms associated with PMS or menopause.
Wild yam root is commonly taken in doses of 1,000 mg per day, and there are no known side effects at this dosage range. Topical creams containing wild yam can be applied liberally with no adverse effects, with the possible exception of allergic reactions in some individuals. Wild yam contains alkaloids which are poisonous in large doses; however, there are no known cases of wild yam toxicity.