Wild Yam

Scientific Name(s): Dioscorea villosa L. Family: Dioscoreaceae (yams).

Common Name(s): Wild yam root , colic root , yuma , devil's bones , rheumatism root , China root , Mexican wild yam

Uses

Clinical trials are generally lacking for topical formulations of Dioscorea for menopausal symptoms. Chinese yam polysaccharides have been evaluated in laboratory studies for potential as prebiotics, with varying results. Dioscorea oppositifolia tubers have been used as a saliva substitute.

Dosing

There are inadequate clinical trials on which to base dosing guidelines.

Contraindications

Contraindications have not been identified.

Pregnancy/Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking.

Interactions

None well documented.

Adverse Reactions

A clinical study evaluating the daily consumption of wild yam reported no adverse events. Topical preparations of wild yam extract are relatively free from adverse effects. Based on a single study in rats, oral D. villosa should be avoided in people with compromised renal function.

Toxicology

Topical D. villosa (with an upper limit of 3.5% diosgenin) was not found to be systemically toxic or genotoxic.

Botany

D. villosa is a twining vine native to the central southeastern US and found less frequently in the Appalachian region. It is a dioecious plant with inconspicuous white to greenish-yellow female flowers and smooth, heart-shaped leaves. Plant synonyms include Dioscorea hirticaulis Bartlett and D. villosa L. var. hirticaulis (Bartlett) H.E. Ahles.

There are more than 500 species of Dioscorea worldwide, with Chinese yam ( D. oppositifolia ), water yam ( Dioscorea alata L. ), and wild yam commonly studied. 1

History

Wild yam was popularized by the Eclectic medical movement in the 19th century for its supposed antispasmodic properties and was therefore prescribed for biliary colic and spasm of the bowel. It was also promoted for the relief of nausea in pregnancy and for amenorrhea and dysmenorrhea. Wild yam has been used for urinary tract infections, rheumatoid arthritis, cholera, nervous excitement, and flatulence. 2 , 3

Chemistry

Extracts of D. villosa contain steroidal saponins, diosgenin, alkaloids, tannins, phytosterols, and starch. 4

Estrogenic compounds have been reported for D. alata . 5

Analytical techniques for the identification of constituents have been described. 4

Uses and Pharmacology

Much of the current herbal use of wild yam is predicated on the misconception that the diosgenin contained in the product can be converted by the human body into steroid hormones, particularly progesterone, through the intermediate dehydroepiandrosterone. This notion appears to be based on historical interest in diosgenin as a synthetic precursor of cortisone. 6 However, evidence suggesting that diosgenin or dioscin can be converted into human hormones is lacking. 7

GI

Chinese yam polysaccharides have been evaluated in laboratory studies for potential as prebiotics, with varying results. 3 , 8 However, clinical studies are lacking.

D. oppositifolia (synonym Dioscorea batatas ) tubers have been used as a saliva substitute. 9 , 10

Menopause

Topical formulations of Dioscorea are poorly evaluated, and it is unlikely that they are a source of progesterone. 11 , 12 , 13 Estrogenic compounds have been reported for D. alata , 5 while weak effects on progesterone receptor activity in human breast cells have also been demonstrated in vitro. 14 Inhibition of human breast cancer MCF-7 cell proliferation was also shown in vitro for D. villosa extracts. 14

Animal data

Research reveals no animal data regarding the use of wild yam for menopausal symptoms.

Clinical data

Limited clinical trials exist evaluating the effect of wild yam and its extract on menopausal symptoms. One uncontrolled clinical study evaluated the effect of consuming 390 g of yam over 30 days and found increases in serum estrone and sex hormone-binding globulin, but not in estradiol. 15 Another randomized, double-blind, placebo-controlled trial evaluated daily topical application of D. villosa extract in menopausal women, finding no change in serum estrogen or progesterone, no effect on symptoms, and no effect on lipids, weight, or blood pressure. 4 , 7 Commercial preparations of topical progesterone creams have been evaluated for use in managing menopausal symptoms (for more information see the Progesterone monograph).

Other uses

Isolated diosgenin decreased total cholesterol and increased high-density lipoprotein in rats. 16

Allantoin from yam decreased plasma glucose in diabetic rats. 17

Dioscorin protein from the tuber of D. alata and Dioscorea japonica showed immune-stimulatory effects in mice 18 , 19 and exhibited hypotensive effects in rats. 20

D. alata was hepatoprotective in rats exposed to acetaminophen. 21

Dosage

There are inadequate clinical trials on which to base dosing guidelines. Commercially available topical preparations of yam extracts recommend the application of 1 teaspoonful of cream twice daily. 7 Based on a single study in rats, oral D. villosa should be avoided in people with compromised renal function. 22

Pregnancy/Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking.

Interactions

None well documented.

Adverse Reactions

A clinical study evaluating the consumption of yam 390 g per day reported no adverse events. 15 Topical preparations of wild yam extract are relatively free from adverse effects. 4 , 7

Acute animal toxicity studies reveal no reno- or hepatotoxicity. 22 A study in rats, however, found an increase in fibrosis in the kidneys and inflammation in the livers of rats fed D. villosa for 28 days. 22

Toxicology

D. villosa has been evaluated in topical preparations with an upper limit of 3.5% diosgenin phytosterol and was not found to be systemically toxic or genotoxic. No data are available on the carcinogenicity of D. villosa . 4

Bibliography

1. Dioscorea villosa L. USDA, NRCS. 2007. The PLANTS Database ( http://plants.usda.gov , March, 2008). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.
2. Brinker F. A comparative review of Eclectic female regulators. J Naturopathic Med. 1996;7:11-26.
3. Kong XF, Zhang YZ, Wu X, et al. Fermentation characterization of Chinese yam polysaccharide and its effects on the gut microbiota of rats. Int J Microbiol . 2009;2009:598152.
4. Final report of the amended safety assessment of Dioscorea Villosa (Wild Yam) root extract. Int J Toxicol . 2004;23(suppl 2):49-54.
5. Cheng WY, Kuo YH, Huang CJ. Isolation and identification of novel estrogenic compounds in yam tuber ( Dioscorea alata Cv. Tainung No. 2). J Agric Food Chem . 2007;55(18):7350-7358.
6. Ulbricht C, Basch E, Ulbricht C, et al. Wild yam (Dioscoreaceae). J Herb Pharmacother . 2003;3(4):77-91.
7. Komesaroff PA, Black CV, Cable V, Sudhir K. Effects of wild yam extract on menopausal symptoms, lipids and sex hormones in healthy menopausal women. Climacteric . 2001;4(2):144-150.
8. Iwata E, Hotta H, Goto M. The screening method of a bifidogenic dietary fiber extracted from inedible parts of vegetables. J Nutr Sci Vitaminol (Tokyo) . 2009;55(4):385-388.
9. Park MS, Chang JY, Kim YY, Kang JH, Kho HS. Physical and biological properties of yam as a saliva substitute. Arch Oral Biol . 2010;55(2):177-183.
10. Syed R, Au K, Cahill C, et al. Pharmacological interventions for clozapine-induced hypersalivation. Cochrane Database Syst Rev . 2008;16;(3):CD005579.
11. Carroll DG. Nonhormonal therapies for hot flashes in menopause. Am Fam Physician . 2006;73(3):457-464.
12. Haimov-Kochman R, Hochner-Celnikier D. Hot flashes revisited: pharmacological and herbal options for hot flashes management. What does the evidence tell us? Acta Obstet Gynecol Scand . 2005;84(10):972-979.
13. Kelley KW, Carroll DG. Evaluating the evidence for over-the-counter alternatives for relief of hot flashes in menopausal women. J Am Pharm Assoc (2003) . 2010;50(5):e106-e115.
14. Park MK, Kwon HY, Ahn WS, Bae S, Rhyu MR, Lee Y. Estrogen activities and the cellular effects of natural progesterone from wild yam extract in mcf-7 human breast cancer cells. Am J Chin Med . 2009;37(1):159-167.
15. Wu WH, Liu LY, Chung CJ, Jou HJ, Wang TA. Estrogenic effect of yam ingestion in healthy postmenopausal women. J Am Coll Nutr . 2005;24(4):235-243.
16. Son IS, Kim JH, Sohn HY, Son KH, Kim JS, Kwon CS. Antioxidative and hypolipidemic effects of diosgenin, a steroidal saponin of yam ( Dioscorea spp.), on high-cholesterol fed rats. Biosci Biotechnol Biochem . 2007;71(12):3063-3071.
17. Niu CS, Chen W, Wu HT, et al. Decrease of plasma glucose by allantoin, an active principle of yam ( Dioscorea spp.), in streptozotocin-induced diabetic rats. J Agric Food Chem . 2010;24;58(22):12031–12035.
18. Liu YW, Liu JC, Huang CY, Wang CK, Shang HF, Hou WC. Effects of oral administration of yam tuber storage protein, dioscorin, to BALB/c mice for 21-days on immune responses. J Agric Food Chem . 2009;57(19):9274-9279.
19. Lin PL, Lin KW, Weng CF, Lin KC. Yam storage protein dioscorins from Dioscorea alata and Dioscorea japonica exhibit distinct immunomodulatory activities in mice. J Agric Food Chem . 2009;57(11):4606-4613.
20. Liu YH, Lin YS, Liu DZ, et al. Effects of different types of yam ( Dioscorea alata ) products on the blood pressure of spontaneously hypertensive rats. Biosci Biotechnol Biochem . 2009;73(6):1371-1376.
21. Lee SC, Tsai CC, Chen JC, et al. Effects of “Chinese yam” on hepato-nephrotoxicity of acetaminophen in rats. Acta Pharmacol Sin . 2002;23(6):503-508.
22. Wojcikowski K, Wohlmuth H, Johnson DW, Gobe G. Dioscorea villosa (wild yam) induces chronic kidney injury via pro-fibrotic pathways. Food Chem Toxicol . 2008;46(9):3122-3131.

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