Other common name(s): wild Mexican yam, colic root, rheumatism root, Chinese yam, shan yao
Scientific/medical name(s): Dioscorea villosa, Dioscorea oppositifolia or Dioscorea opposita, Dioscorea batatas
Wild yam is a perennial vine, also known as the wild Mexican yam or Dioscorea villosa, which is native to North America. A similar variety called the Chinese yam is an ornamental plant native to China that now grows in North America as well. It is known as Dioscorea oppositifolia and Dioscorea batatas but is called shan yao in Chinese herbal medicine. The roots and rootstock, or rhizomes, of both types of yam are used in herbal remedies. These plants are different from the yams and sweet potatoes commonly eaten in North America.
Although creams and oral supplements containing wild yam extracts are popular among women as an alternative to postmenopausal hormone therapy, available scientific evidence does not support claims that they are safe or effective. Neither estrogen nor progesterone can be found in wild yams, although these yams may contain compounds that have effects similar to, but milder than, estrogen. Some wild yam creams have synthetic (sometimes called "natural") progesterone added to them.
How is it promoted for use?
The wild Mexican yam and the Chinese yam are 2 types of yams that are promoted in similar ways. Proponents claim that a cream made from the wild Mexican yam contains natural progesterone (a hormone that plays a vital role in women's health) and is therefore effective in treating premenstrual syndrome (PMS) and menstrual irregularity, as well as hot flashes and other symptoms of menopause. Supporters say that using wild yam as an alternative to postmenopausal hormone therapy significantly lowers the risk of breast and endometrial cancer. Marketers also claim that their product helps women lose weight, increases energy and stamina, and enhances sex drive. A few marketers imply that wild yam can be used as herbal birth control. By contrast, some suggest that it improves fertility. It is also recommended to enlarge breasts and reduce wrinkles.
Supporters claim that the wild Mexican yam, when taken internally, helps arthritis pain, morning sickness, painful menstruation, bronchitis, asthma, whooping cough, cramps, and intestinal ailments such as Crohn’s disease, colitis, and chronic diarrhea.
The Chinese yam is claimed to stimulate appetite and to be a remedy for chronic diarrhea, asthma, fatigue, uncontrollable or frequent urination, diabetes, and emotional instability. Proponents claim the Chinese yam can be used externally to speed the healing of boils and abscesses. Herbalists also use it to treat colic because it is thought to relieve intestinal spasms.
What does it involve?
Creams or gels made from wild yams are rubbed directly onto the skin and are available from health food stores and on the Internet. Some of these creams have synthetic, or man-made, progesterone added to them, although most don’t advertise this addition; if they do, it is often mentioned as natural progesterone. Wild yam is also sold as a capsule, liquid, dried root, and tincture to be taken by mouth. Some sellers combine it with vitamins, minerals, or other herbs, such as black cohosh (see Black Cohosh). In homeopathic medicine, the wild yam from the Dioscorea villosa plant is used fresh or dried and put in liquid extracts (see Homeopathy). The Chinese yam can also be used fresh or baked with flour or clay. Wild yam capsules and other forms are available in herbal shops and over the Internet. Dosages vary by manufacturer.
What is the history behind it?
In East Indian traditional medicine, the wild yam is used to treat sexual and hormonal problems. Chinese herbalists have long used the herb for rheumatism, asthma, and digestive and urinary complaints. Wild yam has also been used in American folk medicine to treat coughs and to induce sweating and vomiting. Some sources suggest that Native Americans and early settlers used it for its ability to relieve intestinal spasms, which is how it got the name colic root.
In the 1960s, progesterone and other steroid hormones were chemically manufactured, in part using ingredients from the Mexican wild yam. This may be the reason for the misconception that the progesterone “precursors” in wild yam could be converted into progesterone in the body.
Some wild yam creams have been found to contain added synthetic progesterone.
What is the evidence?
Contrary to claims, wild yam cannot supply the body with progesterone. The plant contains the chemical diosgenin, which can be converted into a synthetic form of progesterone through a lengthy process in the laboratory. There is no available scientific evidence that suggests the body can convert diosgenin into progesterone. Some of the chemicals in the plant resemble a weak form of estrogen, another hormone that is important in female physiology, but estrogen’s effects on the body are very different from those of progesterone. Drugs manufactured from diosgenin are used to treat asthma, arthritis, eczema, and to control fertility.
Available scientific evidence does not support claims that the wild yam can help the symptoms of menopause or premenstrual syndrome, reduce wrinkles, or enlarge breasts. However, since progesterone is absorbed through the skin and mucous membranes, a wild yam cream with added progesterone can have pharmacologic effects on the whole body.
Are there any possible problems or complications?
This product is sold as a dietary supplement in the United States. Unlike companies that produce drugs (which must provide the FDA with results of detailed testing showing their product is safe and effective before the drug is approved for sale), the companies that make supplements do not have to show evidence of safety or health benefits to the FDA before selling their products. Supplement products without any reliable scientific evidence of health benefits may still be sold as long as the companies selling them do not claim the supplements can prevent, treat, or cure any specific disease. Some such products may not contain the amount of the herb or substance that is written on the label, and some may include other substances (contaminants). Though the FDA has written new rules to improve the quality of manufacturing processes for dietary supplements and the accurate listing of supplement ingredients, these rules do not take full effect until 2010. And, the new rules do not address the safety of supplement ingredients or their effects on health when proper manufacturing techniques are used.
Most such supplements have not been tested to find out if they interact with medicines, foods, or other herbs and supplements. Even though some reports of interactions and harmful effects may be published, full studies of interactions and effects are not often available. Because of these limitations, any information on ill effects and interactions below should be considered incomplete.
Large doses of wild yam can cause nausea, vomiting, and diarrhea. Women who are pregnant or breast-feeding should not use wild yam. Although rare, allergic reactions to wild yam can occur, including rashes, asthma, and other symptoms.
There are several problems with using wild yam creams with added progesterone. They are often not labeled as containing added progesterone, and the amount in the cream varies. Even if the amount of progesterone in the cream was consistent and declared, the body absorbs progesterone in different amounts at different times and from different places on the body. This means that any effect on the body is unreliable. In addition, progesterone can have side effects such as headache, breast tenderness, upset stomach, constipation, tiredness, and irritability. In rare cases, there can be serious side effects, such as dizziness, faintness, shortness of breath, blurred vision, seizures, and swelling of the lips, mouth, or throat. Relying on this type of treatment alone and avoiding or delaying conventional medical care for cancer may have serious health consequences.
More information from your American Cancer Society
The following information on complementary and alternative therapies may also be helpful to you. These materials may be found on our Web site (www.cancer.org) or ordered from our toll-free number (1-800-ACS-2345).
The ACS Operational Statement on Complementary and Alternative Methods of Cancer Management
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Note: This information may not cover all possible claims, uses, actions, precautions, side effects or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for consultation with your doctor, who is familiar with your medical situation.
Last Revised: 11/28/2008