Yam: Dioscorea villosa
In the 18th and 19th centuries, herbalists used wild yam (Dioscorea villosa) to treat menstrual cramps and problems related to childbirth, as well as for upset stomach and coughs. In the 1950s, scientists discovered that the roots of wild yam -- not to be confused with the sweet potato yam -- contain diosgenin. Diosgenin is a phytoestrogen, or plant-based estrogen, that can be chemically converted into a hormone called progesterone. Diosgenin was used to make the first birth control pills in the 1960s.18
Early Americans used wild yam to treat colic, a reason for another name for the plant, colic root. Traditionally, it has been used to treat inflammation, muscle spasms, and a range of disorders, including asthma. However, there is no scientific evidence that it works. Several studies show wild yam has powerful antifungal properties and may help fight yeast and other fungal infections.18
Although herbalists continue to use wild yam to treat menstrual cramps, nausea and morning sickness, inflammation, osteoporosis, menopausal symptoms, and other health conditions, there's no evidence to show it works for these uses. Several studies have found that it has no effect at all. That is because the body cannot change diosgenin into progesterone; it has to be done in a lab. Wild yam, by itself, does not contain progesterone.
Chinese yam, also known as Dioscorea opposita or Shan Yao in Pinyin, has long been used as a congenital and acquired tonic, earning it the name “fairy food.” Among all cooking methods, stir-fried thick yam slices and yam stew are the most common practices. Well, what is Chinese yam good for? From the perspective of traditional Chinese medicine, Chinese wild yam is credited with tons of health benefits since it is good at tonifying kidney and spleen. [Traditional Chinese Medicine] believes that the kidney is the congenital origin and in charge of heredity and fertility while the spleen is the acquired foundation and responsible for digestion and absorption, which thus is the main source of body’s nutrition. So to speak, it benefits both the root of innate and acquired constitution, which is quite rare in dietary therapy.
Wild yam was used as a medicinal herb by the Mayans as the Aztecs, possibly as a pain treatment. In North America, the herb is known by the English common names “colic Root” and “rheumatism Root”, suggesting that the Native Americans and the first European settlers primarily used it as a remedy for colic and gout.
Dioscorea strydomiana is a recently discovered yam from South Africa. It is critically endangered and one of the most unusual yam species anywhere in the world.21
Only two populations totaling about 200 plants are known in the wild. This species is believed to provide a cure for cancer in the region where it grows, and is consequently under threat from over-exploitation by medicinal plant collectors, who remove parts of the tubers.21
Dioscorea strydomiana is used locally with another species of Dioscorea to treat cancer. Its efficacy is unknown. The related species D. elephantipes and D. sylvatica are known to contain high levels of steroidal compounds which can be used to reduce inflammation, for example in the treatment of arthritis or for the promotion of healing.
Dioscorea composita or barbasco is a species of yam in the genus Dioscorea, native to Mexico.
Before becoming used industrially the tuber was used by Chinantec healers in northern Oaxaca as an abortifacient and in cures for aching joints. It was also used by chinantecs as a poison for fishing in the Papaloapan river, and is also mentioned in use for this purpose in the Popol Vuh, the sacred book of the K'iche maya.