Wild Yam (Dioscorea villosa)
1. Identity
Botanical and Chemical Names
Wild yam is commonly known as colic root, rheumatism root, devil's bones, and fourleaf yam. Synonyms of Dioscorea villosa include Dioscorea hirticaulis and Dioscorea villosa var. hirticaulis. The genus name Dioscorea derives from the ancient Greek physician Pedanius Dioscorides. Additional common names in other languages include shan yao (Chinese), igname (French), name silvestre (Spanish), and Vildjams (Swedish).
There are two main botanical sources: one with the Latin name Dioscorea villosa is from North America (mainly Mexico), while the other, Dioscorea oppositifolia (or Dioscorea opposita), is from China. There are an estimated 600 species of yam in the genus Dioscorea, many of them wild species that flourish in damp woodlands and thickets, and not all contain diosgenin. The plant belongs to the family Dioscoreaceae and is classified taxonomically distinct from edible sweet potatoes or culinary yams found in grocery stores. Wild yam used in wellness formulas, known scientifically as Dioscorea villosa, is a completely different plant than the sweet potatoes or so-called "yams" commonly found in grocery stores.
Plant Description and Natural Source
It is common and widespread in a range stretching from Texas and Florida north to Minnesota, Ontario, and Massachusetts. Wild yam is a perennial vine that can grow up to 9 feet in length. It has heart-shaped leaves and produces clusters of small, greenish-white flowers. This perennial, twining vine grows in damp woodlands and thickets. The parts used medicinally are the root and rhizome.
Commercial Forms and Preparations
Wild yam is available in various forms, including capsules, tinctures, creams, and teas, and is often marketed as a natural remedy for menopause and hormonal support. Industry-reported uses include body and hand creams, lotions, powders, and sprays at a concentration of 0.00001%, and moisturizing creams, lotions, powders, and sprays at concentrations up to 15%. Popular specifications of wild yam root extract include preparations standardized to 6%, 10%, 16%, 95%, and 98% diosgenin, as well as ratio extracts of 4:1 and 10:1.
2. Traditional and Historical Use
Native American Traditions
Some of the English common names of this plant reflect its use in Native American and other traditional medicines. Native Americans in the southeast cultivated this plant. Wild yams have been used historically by the Meskwaki primarily to soothe labor pains; however, there are records of physicians using the root in an attempt to cure various respiratory issues, as well as rheumatism and morning sickness. Indigenous peoples of North America used wild yam for various purposes, including women's health issues, digestive disorders, and pain relief.
Wild yam was used as a medicinal herb by the Mayans and Aztecs, possibly as a pain treatment. In North America, the herb is also known by the common names "colic root" and "rheumatism root," suggesting that Native Americans and the first European settlers primarily used it as a remedy for colic and gout.
Eclectic Medicine and Formal Medical Use
Wild yam was used by Native Americans and Eclectic physicians for a wide variety of complaints relating to spasmodic contractions of the hollow viscera, ranging from bilious colic to dysmenorrhea. It was included in the National Formulary (NF) from 1916 to 1942 as a diaphoretic and expectorant. Wild yam has been used historically to treat spastic, dyspeptic pain of the abdomen, uterus, and gallbladder, and was highly popular among Eclectic physicians as an antispasmodic treatment for dysmenorrhea with spasmodic, colicky pains, for which it was given every few hours.
Wild yam was used by Eclectic medical physicians for the treatment of nausea and vomiting of pregnancy (NVP) and by Native American tribes to ease childbirth, suggesting some historical expectation of its safety during pregnancy.
Russian and Japanese Traditions
In traditional Russian herbal medicine, saponin extracts from the roots of various varieties of wild yam are thought to be an anticoagulant, antisclerotic, antispasmodic, cholagogue, depurative, diaphoretic, diuretic, and a vasodilator. It has a persevering history in Japanese medicine where it was used as a treatment for infertility and for the pain of childbirth.
Introduction to European Herbalism
The importance of wild yam throughout history dates back to Native American cultures, where it was valued for its nutritional content and medicinal benefits. By the 18th century, wild yams were introduced to European settlers, who saw it used in local herbal remedies and occasionally used it as a food crop.
The 20th-Century Pharmaceutical Breakthrough
The confusion between yam extract and progesterone has its roots in a genuine scientific breakthrough. In the 1940s, American chemist Russell Marker developed a method for converting diosgenin — a plant steroid found abundantly in wild Mexican yams — into progesterone in the laboratory. This discovery revolutionized hormone production and made it possible to manufacture affordable progesterone and other steroid hormones on a commercial scale.
The first large-scale application of this route took place in 1943, when Russell Earl Marker collected 10 tons of yam tubers to synthesize 3 kilograms of progesterone, which was the largest single amount of progesterone that had been produced by that time. Subsequently, diosgenin was used as starting material for the synthesis of cortisone and norethindrone. The latter became known as a highly potent and orally active progestational agent and was the key ingredient in the first birth control pills in the 1960s.
Progesterone continued to be manufactured from wild yam for decades until a cheaper source of raw material was found in cultivated soybeans. Neither soybeans nor wild yams, however, contain progesterone. They contain only chemicals that chemists can use as a starting point to manufacture progesterone.
In the past decade, wild yam has enjoyed a resurgence in popularity based on the erroneous assumption that because it contains steroidal saponins used in the manufacture of progesterone for oral contraceptive pills (OCPs), it could be taken as an herb to increase progesterone levels and thus treat a variety of gynecologic complaints.
3. Key Constituents and Active Compounds
Primary Phytochemical Profile
The extract of Dioscorea villosa root contains glycoside and steroidal saponins (≤0.4%), diosgenin (≤3.5%), alkaloids, tannins, phytosterols, and starch. A 2013 study published in PMC also identified a secondary class of constituents: a fractionation methodology aimed at the metabolomic mining of new phytoconstituents for wild yam (Dioscorea villosa) led to the isolation of 14 diarylheptanoids, including five new compounds with a tetrahydropyrano core skeleton.
Diosgenin: The Principal Active Compound
Diosgenin is a well-known steroid sapogenin derived from plants and has been used as a starting material for the production of steroidal hormones. This steroid sapogenin is the primary active compound in wild yam. Structurally, diosgenin belongs to the spirostanol class of steroidal saponins.
The diosgenin-to-hormone conversion debate is central to understanding wild yam's pharmacology. Contrary to popular claims, diosgenin is not converted to steroids in vivo. Wild yam roots do not contain and are not converted into progesterone or dehydroepiandrosterone (DHEA) in the body. This conversion requires a multi-step chemical synthesis that can only be performed in a laboratory setting. The human body simply does not possess the enzymes needed to convert diosgenin into progesterone. Diosgenin, extracted from the tubers of Dioscorea villosa, has been promoted as a natural form of DHEA, yet the chemical reaction needed to convert diosgenin into DHEA is not known to occur in the human body. Ingesting the yam extract has not been found to increase DHEA levels in humans.
Any increase in progesterone associated with using topical creams was due to the inclusion of USP-grade synthetic progesterone in those products.
Other Notable Constituents
Dioscorin, another protein found in wild yam, appeared to reduce weight gain and total visceral lipids, and improve impaired glucose tolerance in mice. Wild yam also contains a chemical called dioscoretine, which has been shown to regulate blood sugar levels in animal models.
Established Mechanisms of Action
Diosgenin has shown a vast range of pharmacological activities in preclinical studies. It exhibits anticancer, cardiovascular protective, anti-diabetes, neuroprotective, immunomodulatory, estrogenic, and skin protective effects, mainly by inducing apoptosis, suppressing malignant transformation, decreasing oxidative stress, preventing inflammatory events, promoting cellular differentiation and proliferation, and regulating T-cell immune response.
Anti-inflammatory mechanisms: Data from in vitro macrophage studies suggest that diosgenin reduces the production of inflammatory mediators by inhibiting LPS/IFN-γ–triggered CK2, JNK, NF-κB, and AP-1 activation. Pretreatment with diosgenin resulted in the inhibition of nitric oxide (NO) production and iNOS expression in a concentration-dependent manner. In addition, diosgenin inhibits production of reactive oxygen species (ROS), interleukin-1 (IL-1), and IL-6. A separate 2023 PubMed-indexed study found that the anti-inflammatory mechanism of diosgenin is related to altering macrophage polarization by activating PPARγ and inhibiting NF-κB signaling pathways.
Antioxidant activity: Diosgenin improves antioxidant status and inhibits lipid peroxidation. It also promotes the synthesis of antioxidant enzymes such as glutathione peroxidase and superoxide dismutase.
Estrogenic signaling: Diosgenin drives cellular growth and differentiation through the estrogen receptor (ER) cascade and transcriptional factor PPARγ. However, diosgenin, despite claims, is not a phytoestrogen and does not interact with estrogen receptors in the same direct manner as classical phytoestrogens; its weak hormonal activity is inconsistent across studies. Diosgenin may stimulate mammary tissue growth, decrease GI inflammation, and weakly stimulate estrogen receptors according to available preclinical data.
Hepatoprotective mechanisms: Diosgenin is a herbal steroidal sapogenin with hepatoprotective properties. This phytosteroid modulates lipid profile and prevents liver injury and fibrosis, metabolic-associated fatty liver disease, steatohepatitis, and diabetes mellitus. Diosgenin with antioxidant activity and ability to inhibit pro-inflammatory and apoptotic mediators as well as modulating gut microbiota is able to protect the liver.
4. Scientific Evidence by Area of Use
4a. Menopausal Symptoms
This is the most studied area of wild yam application and the one with the most clearly negative findings from clinical trials. There is limited mixed evidence on whether wild yam might be helpful for menopausal symptoms.
Key clinical trial (Komesaroff et al., 2001): Many women seek alternatives to hormonal therapies for the management of menopausal symptoms. Among the treatments currently popular are extracts of wild yam (Dioscorea villosa), applied topically in the form of a cream. These preparations are known to contain steroidal saponins, including diosgenin, which has been claimed to influence endogenous steroidogenesis. However, there had been no studies of the safety or efficacy of these preparations prior to this work. A double-blind, placebo-controlled, cross-over study was conducted on 23 healthy women suffering from troublesome symptoms of menopause. Both study groups showed minimal improvement on flushing severity and number, with no significant difference between wild yam extract and placebo. After 3 months of therapy, there was no change in FSH, estradiol, or serum or salivary progesterone. Therefore, while wild yam extract appears to be well tolerated without significant side effects, it also does not appear to be beneficial for the treatment of menopausal symptoms.
Taiwanese dietary yam study: A study examining hormone levels in Taiwanese postmenopausal women after yam extract ingestion found that 24 women who replaced their daily dietary staple of rice with a wild yam supplement for 30 days showed a 26% increase in serum estrone levels and a nearly 10% increase in sex-hormone-binding globulin levels, with a lesser increase in serum estradiol. The clinical relevance of this finding is uncertain, as estrone is a weaker form of estrogen typically seen in postmenopausal women not on HRT.
Overall evidence quality: A standardized, evidence-based rating system showed poor efficacy scores for wild yam, indicating fair scientific evidence against its use for alleviating menopausal symptoms. A review by the National Institutes of Health (NIH) states that there is insufficient evidence to recommend wild yam for menopausal symptoms like hot flashes. Clinical studies, including a notable double-blind trial, showed that wild yam did not alleviate menopausal symptoms or affect hormone levels in women.
4b. Anti-Inflammatory and Antispasmodic Effects
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.
Mechanistic evidence in this area is largely preclinical. Animal models suggest antinociceptive, anti-inflammatory, and antidiabetic effects. At the cellular level, the inhibition of NF-κB and related pro-inflammatory pathways by diosgenin is well characterized in cell-based assays (see Section 3 above). Wild yam continues to be one of the primary uterine antispasmodics used for dysmenorrhea by contemporary herbalists. No contemporary research is available on its effects on the uterine muscle.
For rheumatoid arthritis specifically, diosgenin can inhibit the proliferation and migration of rheumatoid arthritis (RA) synovial cells. Diosgenin also reduces the inflammatory response of RA synovial cells, during which the expression of PDE3B is significantly decreased. These findings are from in vitro studies only and have not been reproduced in human clinical trials. Supporting evidence for the treatment of rheumatoid arthritis is lacking from clinical studies.
4c. Blood Glucose Regulation and Antidiabetic Activity
Wild yam contains a chemical called dioscoretine, which has been shown to regulate blood sugar levels. Wild yam could be useful in regulating blood sugar levels in people with diabetes; however, the effect of dioscoretine on blood sugar has only been studied in animals so far. It is unclear whether it would have the same effect in humans.
In a rodent study published on PubMed, the daily oral administration of diosgenin at different doses (15, 30, and 60 mg/kg body weight) to diabetic rats for 45 days resulted in a significant decline in blood glucose level and a significant increase in plasma insulin level. The altered activities of carbohydrate metabolic key enzymes in muscle and kidneys of diabetic rats were significantly reverted to near-normal levels. The obtained results were compared with glibenclamide, a standard oral hypoglycemic drug. The modulatory effects of diosgenin on attenuating the activities of carbohydrate metabolic enzymes afford a promise for persistent use for the treatment of diabetes in the future, even though clinical studies to evaluate this possibility may be warranted. Evidence in humans remains absent.
4d. Lipid Metabolism and Cardiovascular Effects
There is abundant evidence that diosgenin has potential for application in correcting lipid metabolism disorders, based on evaluations of both clinical and animal studies. Various experiments have demonstrated the lipid-lowering potential of diosgenin. It inhibits cholesterol absorption in serum and low-density lipids in cholesterol-fed rats, suppresses its uptake in serum and accumulation in the liver, and lowers plasma cholesterol in rats, chickens, and rabbits.
Recent data suggest diosgenin plays an anti-atherosclerosis role through its anti-inflammatory, antioxidant, plasma cholesterol-lowering, anti-proliferation, and anti-thrombotic effects. However, poor pharmacokinetic profile, low bioavailability, low aqueous solubility, and instability in the gastrointestinal tract limit the clinical application of diosgenin and its analogs.
A noteworthy human-level finding was reported in a review article: the clinical application of diosgenin has found no changes in weight, systolic or diastolic blood pressure, total serum cholesterol, triglycerides, high-density lipoprotein cholesterol, glucose, or estradiol. The overall evidence remains preclinical in nature; robust human trials on diosgenin for lipid disorders are lacking.
4e. Cognitive Function and Neuroprotection
Preclinical studies have shown promising effects of diosgenin on neuroprotection and other pathologies. Clinical investigations have demonstrated diosgenin's nontoxic nature and promising benefits on cognitive function and menopause. The neuroprotective effect of diosgenin was studied with the SH-SY5Y cell line and H9c2 cell line, which predicted better neuroprotection while reducing apoptosis in brain cells. These studies are preclinical; large-scale human trials are not yet available.
4f. Bone Health
A few studies have explored diosgenin's effects on bone health, lipid metabolism, and inflammation, showing promise but lacking large-scale human trials. Animal research has examined the effect of diosgenin on postmenopausal bone loss: one study reported that diosgenin reduces bone loss in ovariectomized rats and restores gut microbiota composition altered by ovariectomy. These findings are from animal models and have not been validated in human trials.
4g. Hepatoprotective Effects
Diosgenin modulates lipid profile and prevents liver injury and fibrosis, metabolic-associated fatty liver disease, steatohepatitis, and diabetes mellitus. Different mechanisms have been presented underlying the therapeutic properties of diosgenin. Diosgenin with antioxidant activity and ability to inhibit pro-inflammatory and apoptotic mediators as well as modulating gut microbiota is able to protect the liver. These findings are based on in vitro and animal studies; clinical evidence in humans is currently absent.
4h. Potential Anticancer Activity
Wild yam has antiproliferative and antimitotic effects in vitro. 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. One study where 22 women were given 390 g of yam per day for 30 days found that urinary concentrations of the genotoxic metabolite of estrogen, 16α-hydroxyestrone, decreased significantly by 37%, suggesting the potential to reduce breast cancer risk, but clinical trial data are required. The steroid saponin diosgenin in wild yam modulates cell signaling involved in growth, differentiation, apoptosis, and oncogenesis. All anticancer claims remain at the in vitro or observational level; no clinical trials have confirmed these effects.
5. Body Systems and Health Areas
Wild yam and its principal constituent diosgenin have been associated with the following body systems and health areas based on preclinical, traditional, and limited clinical data:
- Female reproductive system: Spasmolytic uses for uterine cramping, dysmenorrhea, chronic pelvic pain, and as an antiemetic for nausea and vomiting of pregnancy.
- Gastrointestinal system: Traditionally used for its antispasmodic and anti-inflammatory properties to treat gastrointestinal ailments and muscle spasm.
- Endocrine/hormonal system: This plant contains diosgenin compounds that are used to produce a variety of modern steroid drugs, as well as hormone-related drugs used as contraceptives and to treat menopause and PMS. As a direct human supplement, hormonal activity is unconfirmed.
- Musculoskeletal system: Traditionally used for joint pain and rheumatoid arthritis.
- Cardiovascular system: Diosgenin and its analogs have gained importance for their efficacy against life-threatening diseases, including cardiovascular and endocrine diseases.
- Hepatic system: Diosgenin is a herbal steroidal sapogenin with hepatoprotective properties based on preclinical evidence.
- Nervous system: Preclinical studies have shown promising effects on neuroprotection and other pathologies. Clinical investigations have demonstrated diosgenin's nontoxic nature and promising benefits on cognitive function.
- Urinary tract: Spasmolytic use in cases of urinary tract infection and interstitial cystitis is described in traditional and naturopathic practice.
6. Dosage Forms and Reported Dosages
The appropriate dose of wild yam depends on several factors such as the user's age, health, and several other conditions. At this time there is not enough scientific information to determine an appropriate range of doses for wild yam. The following dosages have been reported in the literature or clinical contexts:
- Dried root (tea/decoction): Traditional preparations involve 1–2 grams of dried root as a tea or decoction.
- Tincture: 2–4 mL of a 1:5 tincture, taken 1–3 times daily.
- Topical cream (menopausal study): A double-blind, placebo-controlled, crossover study evaluated the effects of wild yam cream on menopausal symptoms, with women treated with either active or placebo cream for 12 weeks in random order. The study used a standardized cream; no specific milligram dose was published in the available abstract data.
- Dietary yam (Taiwanese study): 24 women replaced their daily dietary staple of rice with a wild yam supplement for 30 days.
- Diosgenin (animal studies): The daily oral administration of diosgenin at different doses (15, 30, and 60 mg/kg body weight) to diabetic rats for 45 days resulted in a significant decline in blood glucose levels. These doses have not been studied in humans.
- Topical cosmetic products: Industry-reported concentrations in moisturizing preparations range up to 15% (equivalent to 0.5% plant solids).
7. Safety Considerations and Known Interactions
General Safety Profile
Wild yam is considered possibly safe when taken by mouth or applied to the skin. In one clinical study, candidates were treated with wild yam cream or placebo for up to three months, and no significant adverse effects were observed in either treatment group.
Toxicological Data
The wild yam root extract produced via a specified extraction process was tested in acute and short-term toxicity tests, dermal irritation tests, a sensitization test, an ocular irritation test, a rat uterotropic assay, and genotoxicity tests. An acute oral toxicity test produced hypoactivity, piloerection, and dyspnea and a death in 1 of 10 rats at 2 g/kg using the specified extract, but no toxicity in rats given 0.5 g/kg. A dermal toxicity test using the specified extract demonstrated no acute toxicity in rats. Both a 7-day local tolerance test and a 28-day dermal toxicity test in rats produced no significant adverse effects at the maximum tested concentration of 10%.
Adverse Effects
Common side effects (dose-dependent) of wild yam include gastrointestinal upset, nausea, vomiting, diarrhea, headache, allergic reactions, and scar tissue in the kidney or liver with prolonged use. While topical use is generally considered safe, there is no research on its potential long-term effects. Creams and ointments may irritate the skin in individuals who are allergic or sensitive to wild yam. Small amounts of wild yam root supplements appear safe to ingest, but larger doses could cause vomiting.
Contraindications
Wild yam is contraindicated in hormone-sensitive cancers of the breast, ovaries, and uterus; endometriosis; uterine fibroids; and other hormone-sensitive conditions. In protein S deficiency, avoidance is advised due to potential increased risk of clot formation. Large amounts might cause vomiting, upset stomach, and headache. It can cause skin irritation or allergic reactions when applied topically. Oral wild yam should be avoided in individuals with compromised renal function.
There is one case report of a patient with protein S deficiency and systemic lupus erythematosus (SLE) who developed a clot in the vein serving the retina in her eye 3 days after taking a combination product containing wild yam, dong quai, red clover, and black cohosh. This single case report cannot establish causality but highlights a plausible mechanism of risk.
Pregnancy and Lactation
It is not known whether wild yam will harm an unborn baby, and use is not advised without medical guidance during pregnancy. It is also not known whether wild yam passes into breast milk or if it could harm a nursing baby, so use without medical advice is not recommended during breastfeeding.
Drug Interactions
Wild yam root may interact with estradiol, a hormone present in some forms of birth control and hormone replacement therapies. As with most dietary supplements, the research on drug interactions with wild yam is incomplete. No severe drug interactions have been formally documented, but the theoretical estrogenic activity of diosgenin suggests caution when co-administered with hormone-based medications.
Product Quality and Adulteration Concerns
Some wild yam products may contain synthetic progesterone, but the "wild yam" label can be misleading. Any increase in progesterone associated with using topical creams was due to the inclusion of USP-grade synthetic progesterone in those products. Consumers and practitioners should be aware that standardization and quality control vary substantially across commercial products.
Conservation Status
There is a very limited market for farmed D. villosa, meaning that almost all of the product on the market is gathered in the wild. This increasing market can put a serious strain on established populations and prevent new colonies from establishing.
References
- ScienceDirect — Wild Yam monograph chapter (Botanical Name, Constituents, Principal Uses)
- PubMed — Final report of the amended safety assessment of Dioscorea Villosa (Wild Yam) root extract. Int J Toxicol. 2004
- PMC — Diarylheptanoids from Dioscorea villosa (Wild Yam). J Nat Prod. 2013
- PubMed — Komesaroff PA et al. Effects of wild yam extract on menopausal symptoms, lipids and sex hormones in healthy menopausal women. Climacteric. 2001
- PubMed — Diosgenin inhibits macrophage-derived inflammatory mediators through downregulation of CK2, JNK, NF-κB and AP-1 activation. 2010
- PubMed — Diosgenin alters LPS-induced macrophage polarization by activating PPARγ/NF-κB signaling pathway. 2024
- PubMed — Advances in the pharmacological activities and mechanisms of diosgenin. Fitoterapia. 2015
- PubMed — Diosgenin: Mechanistic insights on its anti-inflammatory effects. 2022
- PubMed — Diosgenin and Its Analogs: Potential Protective Agents Against Atherosclerosis. 2022
- PubMed — Diosgenin Inhibits Excessive Proliferation and Inflammatory Response of Synovial Fibroblasts in Rheumatoid Arthritis by Targeting PDE3B. 2021
- PubMed — Modulatory effects of diosgenin on attenuating the key enzymes activities of carbohydrate metabolism and glycogen content in streptozotocin-induced diabetic rats. 2014
- PMC — Literature review on hepatoprotective effects of diosgenin: possible mechanisms of action. 2023
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