Wild yam has not been shown to prevent or treat cancer.
Wild yam contains a compound called diosgenin that mimics estrogen and progesterone in animals. Diosgenin can be converted into active steroid compounds in the lab. Small studies using different species and formulas of wild yam extract have had mixed results on menopausal symptoms. Another small study suggests that increasing yam intake through diet may improve sex hormone and cholesterol levels. A lab study showed that wild yam extract has weak hormonal activity against human breast cancer cells, but this does not mean it can prevent or treat cancer.
More studies are needed to confirm whether wild yam or its extract actually has any benefits. Because wild yam has estrogenic effects, patients with hormone-sensitive cancers should talk to their physicians before consumption.
To relieve menopausal symptoms
Wild yam has had mixed results in small studies. More research is needed.
To improve cough
Supporting evidence is lacking.
To treat rheumatoid arthritis
Supporting evidence is lacking.
Animal studies have shown wild yam extract may cause kidney injury. But clinical significance is not known.
Dioscorea villosa, Dioscorea alata
Derived from the root of a twining vine, wild yam was traditionally used for its antispasmodic and anti-inflammatory properties to treat menopausal symptoms, gastrointestinal ailments, muscle spasm, asthma, joint pain, and rheumatoid arthritis (1)(2). Wild yam has antiproliferative (3) and antimitotic effects (4) in vitro, and animal models also suggest it has antinociceptive and anti-inflammatory properties (1)(18). Diosgenin, the active ingredient in wild yam, was shown to have estrogenic and progestogenic effects (3)(5)(6)(7)(19), and to restore moderately decreased sperm motility (20) in mice. Dioscorin, another protein, was shown to lower weight gain, total visceral lipids, and impaired glucose tolerance in mice (21).
Two small studies on whether wild yam can relieve menopausal symptoms had opposing results, with one demonstrating an oral D. alata formula to be more effective than placebo (8), but another study showing a topical D. villosa formula to be ineffective (9). A study of dietary yam was found to improve sex hormone and lipid profiles (10). More studies are needed to confirm whether dietary or supplemental wild yam actually has any benefits for menopausal symptoms. Consuming an oral diosgenin-rich yam extract was shown to enhance cognitive function (22).
Wild yam extract is sold as a dietary supplement, liquid extract or as a cream. Diosgenin in wild yam has been used as raw material for synthetic progesterone, but there is no evidence that the human body can convert diosgenin into progesterone. Because wild yam has estrogenic effects, patients with hormone-sensitive cancers should talk to their physicians before consumption.
Mechanism of Action
The steroid saponin diosgenin in wild yam modulates cell signaling involved in growth, differentiation, apoptosis, and oncogenesis (14). In vitro studies suggest wild yam extract protects against human breast cancer proliferation by acting as a weak phytoestrogen (3). A molecular docking study of estrogen mimics in phytochemicals from dietary herbal supplements found that D. villosa docked strongly with the estrogen receptor (23). However, the D. villosa species has been noted to induce chronic kidney injury via pro-fibrotic pathways in animal models (15).
Animal models indicate a potential for kidney injury. However, the clinical relevance is not known (15).