Wild yam

Related Terms

Atlantic yam, barbasco, batata silvestre, black yam, China root, colic root, devil's bones, Dioscorea, Dioscorea barbasco, Dioscorea hypoglauca, Dioscorea macrostachya, Dioscorea opposita, Dioscorea villosa, Dioscoreae (family), diosgenin, Mexican yam, natural DHEA, phytoestrogen, potassium, rheumatism root, shan yao, white yam, wild yam root, yam, yellow yam, yuma.
Note: "Yams" sold in the supermarket are members of the sweet potato family and are not true yams.

Background

It has been hypothesized that wild yam (Dioscorea villosa and other Dioscorea species) possesses dehydroepiandrosterone (DHEA)-like properties and acts as a precursor to human sex hormones such as estrogen and progesterone. Based on this proposed mechanism, extracts of the plant have been used to treat painful menstruation, hot flashes, and headaches associated with menopause. However, these uses are based on a misconception that wild yam contains hormones or hormonal precursors - largely due to the historical fact that progesterone, androgens, and cortisone were chemically manufactured from Mexican wild yam in the 1960s. It is unlikely that this chemical conversion to progesterone occurs in the human body. The hormonal activity of some topical wild yam preparations has been attributed to adulteration with synthetic progesterone by manufacturers, although there is limited evidence in this area.
The effects of the wild yam saponin constituent "diosgenin" on lipid metabolism are well documented in animal models and are possibly due to impaired intestinal cholesterol absorption. However, its purported hypocholesterolemic effect in humans and the feasibility of long-term use warrant further investigation.
There are few reported contraindications to the use of wild yam in adults. However, there are no reliable safety or toxicity studies during pregnancy, lactation, or childhood.

Evidence Table

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. GRADE *
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. GRADE *


Animal studies have shown that wild yam can reduce the absorption of cholesterol from the gut. Early studies in humans have shown changes in the levels of certain sub-types of cholesterol, including decreases in low-density lipoprotein (LDL, or "bad cholesterol") and triglycerides and increases in high-density lipoprotein (HDL, or "good cholesterol"). However, no changes in the total amount of blood cholesterol have been found. More studies are needed in this area.

 C


Animal studies have shown that wild yam can reduce the absorption of cholesterol from the gut. Early studies in humans have shown changes in the levels of certain sub-types of cholesterol, including decreases in low-density lipoprotein (LDL, or "bad cholesterol") and triglycerides and increases in high-density lipoprotein (HDL, or "good cholesterol"). However, no changes in the total amount of blood cholesterol have been found. More studies are needed in this area.

 C


Most studies have not shown a benefit from wild yam given by mouth or used as a vaginal cream in reducing menopausal symptoms. However, replacing two thirds of staple food with yam for 30 days was shown to improve the status of sex hormones, lipids, and antioxidants in a recent study in postmenopausal women. The authors suggest that these effects might reduce the risk of breast cancer and cardiovascular diseases in postmenopausal women. Further research is needed before a recommendation can be made.

 C


Most studies have not shown a benefit from wild yam given by mouth or used as a vaginal cream in reducing menopausal symptoms. However, replacing two thirds of staple food with yam for 30 days was shown to improve the status of sex hormones, lipids, and antioxidants in a recent study in postmenopausal women. The authors suggest that these effects might reduce the risk of breast cancer and cardiovascular diseases in postmenopausal women. Further research is needed before a recommendation can be made.

 C


Despite popular belief, no natural progestins, estrogens, or other reproductive hormones are found in wild yam. Its active ingredient, diosgenin, is not converted to hormones in the human body. Artificial progesterone has been added to some wild yam products. The belief that there are hormones in wild yam may be due to the historical fact that progesterone, androgens, and cortisone were chemically manufactured from Mexican wild yam in the 1960s.

D


Despite popular belief, no natural progestins, estrogens, or other reproductive hormones are found in wild yam. Its active ingredient, diosgenin, is not converted to hormones in the human body. Artificial progesterone has been added to some wild yam products. The belief that there are hormones in wild yam may be due to the historical fact that progesterone, androgens, and cortisone were chemically manufactured from Mexican wild yam in the 1960s.

D
* Key to grades

A: Strong scientific evidence for this use
B: Good scientific evidence for this use
C: Unclear scientific evidence for this use
D: Fair scientific evidence for this use (it may not work)
F: Strong scientific evidence against this use (it likley does not work)
* Key to grades

A: Strong scientific evidence for this use
B: Good scientific evidence for this use
C: Unclear scientific evidence for this use
D: Fair scientific evidence for this use (it may not work)
F: Strong scientific evidence against this use (it likley does not work)

Tradition / Theory

The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

Dosing

Adults (18 years and older)
There are no proven effective medicinal doses for wild yam.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Interactions

Interactions with Drugs
It is not clear whether blood sugar is lowered by Dioscorea villosa (wild yam). Dioscoretine, a compound found in the related species Dioscorea dumentorum (bitter or African yam), has been shown to lower blood sugar levels, but this has not been shown for Dioscorea villosa. Effects on blood sugar in humans have not been reported. Nonetheless, caution is advised when using medications that may also lower blood sugar. People taking diabetes drugs by mouth or insulin should be monitored closely by a qualified healthcare provider. Medication adjustments may be necessary.
Early evidence suggests that wild yam lowers blood levels of indomethacin, a non-steroidal anti-inflammatory drug, and reduces irritation of the intestine caused by indomethacin. Human studies have not been reported in this area and it is not clear if wild yam affects the blood levels of other anti-inflammatory drugs such as ibuprofen (Advil?, Motrin?).
Diosgenin, thought to be the active substance in wild yam, has been found in animals to reduce absorption of cholesterol from the intestine and to lower total cholesterol levels in the blood. Studies in humans show no change in the total amount of cholesterol in the blood, although the amounts of specific types of cholesterol in the blood may be changed; low-density lipoprotein (LDL, or "bad cholesterol") and triglycerides may be lowered and high-density lipoprotein (HDL, or "good cholesterol") may be increased. It is thought that wild yam may enhance the effects of other cholesterol-lowering medications, including fibric acid derivatives such as clofibrate (Questran?), gemfibrozil (Lopid?), and fenofibrate (Tricor?). In animals, wild yam has been found to improve the effect of clofibrate in lowering cholesterol levels.
Tinctures of wild yam may contain high amounts of alcohol and may lead to vomiting if taken with disulfiram (Antabuse?) or metronidazole (Flagyl?).
An early study suggests that wild yam may interfere with the body's ability to control levels of the reproductive hormone progesterone. Progesterone is a key ingredient in some hormone replacement and birth control pills. There are reports that some wild yam products may be tainted with artificial progesterone. Women taking birth control pills or hormone replacement therapy should speak with a licensed healthcare provider before taking wild yam.
Wild yam may also interact with steroids, although human evidence is lacking.

Attribution

This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography

Araghiniknam M, Chung S, Nelson-White T, et al. Antioxidant activity of Dioscorea and dehydroepiandrosterone (DHEA) in older humans. Life Sciences 1996;59:L147-L157.
Hudson t, Standish L, Breed C, et al. Clinical and endocrinological effects of a menopausal botanical formula. Journal of Naturopathic Medicine 1997;7:73-77.
Komesaroff PA, Black CV, Cable V, et al. Effects of wild yam extract on menopausal symptoms, lipids and sex hormones in healthy menopausal women. Climacteric 2001;4(2):144-150.
Kubo Y, Nonaka S, Yoshida H. Allergic contact dermatitis from Dioscorea batatas Decaisne. Contact Dermatitis 1988;18(2):111-112.
Ulbricht C, Basch E, Ulbricht C, et al. Wild yam (Dioscoreaceae). J Herb Pharmacother 2003;3(4):77-91.
Wu WH, Liu LY, Chung CJ, et al. Estrogenic effect of yam ingestion in healthy postmenopausal women. J Am Coll Nutr 2005;24(4):235-243.