Wild yam

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 dysmenorrheal (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.

Synonyms

Atlantic yam, barbasco, China root, colic root, D. barbasco, D. hypoglauca, D. macrostachya, D. opposita, D. villosa , devil's bones, dioscorea, dioscoreae, diosgenin, Mexican yam, natural DHEA, phytoestrogen, rheumatism root, shan yao, wild yam root, yam, yuma.

Note: "Yams" sold in the supermarket are members of the sweet potato family and are not true yams.

Evidence

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.

Uses based on scientific evidence	Grade^*
High cholesterol Animal studies have shown that wild yam can reduce 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
Menopausal symptoms Most studies have not shown a benefit from wild yam given by mouth or used as a vaginal cream, in reducing menopausal symptoms. However, yam may improve the status of sex hormones, lipids, and antioxidants in a recent study in postmenopausal women. Further research is needed before a recommendation can be made.	C
Hormonal properties (to mimic estrogen, progesterone, or DHEA) 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 against this use;
F: Strong scientific evidence against this use.

Grading rationale

The below uses are based on tradition or scientific theories. 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.

Antifungal, anti-inflammatory, antiviral, asthma, bile flow improvement, biliary colic, breast cancer, breast enlargement, cancer prevention, cardiovascular disease, childbirth, cramps, croup, decreased perspiration, diverticulitis, expectorant, flatus prevention, energy improvement, excessive perspiration, intestinal spasm, irritable bowel syndrome, joint pain, libido, liver protection, low blood sugar, menstrual pain or irregularities, morning sickness, nerve pain, osteoporosis, pelvic cramps, pancreatic enzyme inhibitor, postmenopausal vaginal dryness, premenstrual syndrome, rash, spasms, urinary tract disorders, uterus contraction, vomiting.

Dosing

The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

Adults (18 years and older)

Vaginal creams containing wild yam are available, but there is no widely accepted dose.

Wild yam is also available as a dried root preparation, capsule, or tincture. Safety and effectiveness of these preparations has not been proven. 2-4 grams or 1-2 teaspoons daily of wild yam dried root in two to three divided doses has been used. 250 milligrams of wild yam capsules taken one to three times daily, or 450-900 milligrams per day of Dioscorea extract from wild yam has been used. Also, 4-12 drops or 2-4 milliliters of wild yam tincture taken three to five times daily has been used.

Children (younger than 18 years)

Not enough evidence is available to recommend use in children. Safety and effectiveness have not been proven, and dosing should be supervised by a licensed healthcare provider.

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.

Rubbing the skin with Dioscorea batatas (a yam species related to Dioscorea villosa ) has been reported to cause allergic rash. Workers exposed to Dioscorea batatas in large amounts and for a prolonged time have developed asthma that is made worse by exposure to the yam. A person who is known to have an allergy to Dioscorea batatas may also be allergic to other Dioscorea types.

Side Effects and Warnings

Wild yam given by mouth was reported to cause stomach upset at high doses.

Wild yam was believed in the past to have properties similar to the reproductive hormone progesterone, but this has not been supported by scientific studies. It has been suggested that some wild yam creams might be tainted with artificial progesterone. Based on theoretical hormonal properties and possible progesterone contamination, people with hormone-sensitive conditions should use wild yam products with caution. This caution applies to people who have had blood clots or strokes and to women who take hormone replacement therapy or birth control pills. In addition, women with fibroids, endometriosis, or cancer of the breast, uterus, or ovary should be aware that these are hormone-sensitive conditions that may be affected by agents with hormonal properties.

In animal studies, compounds from the Dioscorea dumentorum species lower blood sugar levels. It is not clear whether wild yam ( Dioscorea villosa ) lowers blood sugar in humans. Caution is advised in patients with diabetes or hypoglycemia and in those taking drugs, herbs, or supplements that affect blood sugar. Blood sugar levels may need to be monitored by a healthcare provider, and medication adjustments may be necessary.

Pregnancy & Breastfeeding

Use of wild yam is not recommended during pregnancy or breastfeeding due to lack of safety information. Wild yam is believed to cause uterine contractions, and therefore use is discouraged during pregnancy. Wild yam was once thought to have effects similar to those of reproductive hormones, although this has not been proven in scientific studies. Artificial progesterone may be added to some products.

Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. 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.

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 in rabbits and rats, 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.

In animals, 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 starting wild yam.

Interactions with Herbs & Dietary Supplements

It is not clear whether Dioscorea villosa (wild yam) lowers blood sugar levels. Although dioscoretine, produced by the related species Dioscorea dumentorum (Bitter or African yam), has been shown to lower blood sugar in rabbits, this reaction has not been seen with Dioscorea villosa and has not been reported in humans. Nonetheless, caution is advised when using herbs or supplements that may also lower blood glucose. Blood glucose levels may require monitoring, and doses may need adjustment.

In an early study, a wild yam preparation was reported to block the body's natural production of progesterone. However, this finding was not supported by later research. There have been several reports that some wild yam products are tainted with synthetic progesterone. Because wild yam may contain progesterone-like chemicals, the effects of other agents believed to have hormone-like properties, in particular those with estrogen-like properties, may be altered.

Wild yam (Dioscoreaceae)

Background

Synonyms

Evidence

Dosing

Safety

Interactions