Dioscorea villosa is one of the species of yam referred to as ‘wild yam’. It is claimed to alleviate symptoms of menopause, but there is no evidence to support this effect.
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Primary Information, Benefits, Effects, and Important Facts
Dioscorea villosa is one of the species of yam referred to as ‘wild yam’.
Dioscorea villosa has been claimed to alleviate symptoms of menopause, but there is currently no evidence to support this effect.
Animal evidence suggests Dioscorea villosa can increase skin thickness after low-dose supplementation. This effect suggests Dioscorea villosa is a potentially useful supplement for skin care, but more research is needed before it can be specifically recommended as a cosmetic supplement.
Dioscorea villosa is claimed to alleviate symptoms of menopause because the molecular structures of the yam are similar to many steroid-like compounds. Dioscorea villosa may have effects similar to Dehydroepiandrosterone (DHEA).
Unfortunately, Dioscorea villosa extracts are associated with kidney and liver fibrosis, a condition characterized by excessive scar tissue. Though this effect is weak, it appears to be both time and dose-dependent. For this reason, chronic supplementation of Dioscorea villosa is not recommended.
Animal studies suggest Dioscorea villosa supplementation provides benefits when 9.8 – 37.7mg/ kg of bodyweight is given to mice. This translates to an approximate human dosage range of 0.8 – 3mg/kg of bodyweight.
Rat studies show that doses of 790mg/kg of bodyweight (126mg/kg of bodyweight in humans) are associated with fibrosis. Lower doses have not been confirmed to be safe.
Since more research is needed to determine whether Dioscorea villosa is safe for supplementation, it cannot currently be recommended.
Dioscorea Villosa is a tuber vegetable that is commonly referred to as 'Wild Yam' and appeared to be recommended for menopausal symptoms and menstrual complaints.[2] The family of Dioscorea refers to Yams in general, with Villosa sometimes being referred to as Wild Yam but the term 'Wild Yam' also being used to refer to many species such as deltoidea, versicolor, bulbifera, and triphylla.[3] The Yam most commonly bought and consumed in first world nations (White Yam) is Dioscorea rotundata with Purple Yams being Dioscorea Alata.
Dioscorea Villosa is one of many species referred to as 'Wild Yam', although the term 'Wild Yam' appears to refer to multiple species
1.2. Composition
Diosgenin is commonly seen as the active ingredient and is an aglycone[4]
Dioscin (Diosgenin glycone) and other glycones of Diosgenin including Dioscin Prosapogenin A,[5] Deltonin,[5] and Diosgenin 3-O-{a-L-rhamnopyranosyl(1fi2)}-{b-D-glucopyranosyl(1fi3)-b-D-glucopyranosyl(1fi4)}-b-D-glucopyranoside[6]
Parvifloside (and Methyl Parvifloside) and two other furostanols, methyl-protodeltonin and trigofoenoside A-1[5][8]
Main component appears to be Diosgenin, and a variety of molecules which are Diosgenin bound to different glycosides; other steroidal saponins appeared to exist in this species of Yam
2Interactions with Neurology
2.1. Menopausal Symptoms
In a trial testing the efficacy of a cream containing Dioscorea Villosa (funded by the suppliers of the supplement, appears to have been conducted independently with no conflict of interest) noted decreased diurnal and non-flushing symptoms (22% and 33%, respectively) but not significantly different than placebo.[1]
This study was confounded as the cream (10% Dioscorea Villosa) also contained Linum usitatissmum, Perlargonium graveolens, and Salvia officinalis with 10mg active Vitamin E; the observed effects cannot thus be attributed to Wild Yam per se. Additionally, a very high dropout rate was noted (23/50 completing the study).[1]
Currently no evidence to support a reduction in menopausal symptoms associated with Dioscorea Villosa
3Interactions with Organ Systems
3.1. Kidneys
An in vitro test assessing renal tubular epithelial cells (NRK52E) of the kidneys noted that the aqueous, methanolic, and ethyl acetate fractions were all able to exert toxicity to these cells and induced α-SMA expression, indicative of fibrotic effects.[9] When rats are fed a diet of 0.72% (790+/-60mg/kg) Dioscorea Villosa over a period of 28 days, although no macroscopic changes are noted with the kidneys there is mild renal tubulo-interstitial fibrosis that develops in a time dependent manner and the increase in α-SMA (and TGFß1) was observed at 28 days yet was sporadic previous to that.[10]
Macrophage accumulation was noted to be not significantly significant globally, but was increased in the glomeruli and interstitial spaces; in the liver, a significant increase was noted in the centrilobular veins and sinusoids.[10]
Preliminary evidence suggests that Wild Yam is weakly fibrotic, but that chronic intake of Wild Yam can result in small fibrosis of the kidney
4Interactions with Cancer
In a large database screening of 374 alternative medicines (herbs, seeds, roots, plankton and fungi) for potential tumoricidal effects it was found that Dioscorea Villosa was the most effective at inducing apoptosis in the tested tumor cell line.[11] In an immortal neuroblastoma cell line (Neuro-2a), Dioscorea Villosa ethanolic extract possessed an LD50 of 19mcg/mL; the study noted that out of 374 tested compounds, only 54 were deemed to be strong (LD50 less than 528mcg/mL) and others in this category included Psoralea fruit, Green Tea, Ginger, Kava, Feverfew, and Black Cohosh as well as both Bloodroot and Dragon's Blood.[11]
Preliminary evidence suggests Dioscorea Villosa may confer anti-cancer effects, but not enough evidence exists to draw many conclusions on efficacy or safety
5Interactions with Hormones
5.1. Estrogen
Diosgenin has thought to act like an estrogen mimetic due to its structural similarity to estradiol, the active form of estrogen in the body.[12]
A study in ovariectomized mice (to mimic menopause) failed to find significant alteration in uterine weight associated with dietary intake of 9.8-37.7mg/kg Diosgenin over a period of 20 weeks, suggesting a lack of estrogenic effects.[13] When mice were implanted with estrogen responsive breast cancer tumors in another experiment, the addition of Diosgenin failed to augment the growth of these tumors (another null result of estrogenicity) although it did not appear to hinder the growth either (possible lack of antagonistic effects).[13]
Does not appear to interact with estrogen; limited evidence
6Interactions with Aesthetics
6.1. Skin
In TESTSKIN cells (a human 3D skin equivalent model), Diosgenin appears to enhance DNA synthesis to a similar potency as retinoic acid (active form of Vitamin A)[13] and at 10nM in human ketatinocytes (isolated from a 70 year old caucasian woman) it appeared to exert these effects via a cAMP dependent pathway (blocked by an inhibitor of adenyl cyclase) that is independent of both estrogen receptors and GPR30.[13]
When Diosgenin was given to (ovariectomized) mice at 0.01-0.04% of the diet for 20 weeks (totalling 9.8-37.7mg/kg), these mice appeared to have improved skin thickness with 0.04% similar to non-ovariectomized control; fat accumulation was not affected.[13]
One study suggesting Diosgenin can enhance skin thickness, which has been demonstrated following oral administration of Diosgenin to mice. In vitro, appears to be relatively potent and mediated by novel means
7Safety and Toxicology
A rat study of safety with consumption of Dioscorea Villosa did not note any harm associated with 500mg/kg but the oral dose of 2000mg/kg was able to induce hypoactivity, piloerection and dyspnoea.[4]
There is limited evidence to suggest adverse effects to the kidneys and liver, which are outlined in the subsection on Kidneys (Interactions with Organ Systems).
