Shan Yao
StarDioscorea opposita Thunb.
Traditionally used for
- Cough & breathing
- Digestion
- Urinary & fluids
- Menstrual & women's health
- Energy & fatigue
☯ TCM Properties
Benefits Qi and Nourishes Yin; Tonifies the Spleen and nourishes the Stomach; Clears Lung Heat and Generates Fluids; Tonifies the Kidneys and astringes Essence; Secures Essence and Stops Leakage
Traditional Chinese Uses
Shan Yao (Chinese yam rhizome) is a neutral, sweet herb that gently tonifies the Spleen, Lung, and Kidney — one of very few herbs to simultaneously supplement three Zang organs. It addresses fatigue, loose stools, and poor appetite from Spleen deficiency; dry cough and shortness of breath from Lung deficiency; and spermatorrhea, excessive vaginal discharge, and frequent urination from Kidney deficiency. As a food that is also a medicine, it is among the safest and gentlest long-term tonics in Chinese medicine.
Western Herbalism Properties
Used In Formulas (10)
Relationships
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Botanical Description
Dioscorea polystachya (frequently treated under its older synonym Dioscorea opposita), commonly known as Chinese yam, cinnamon vine or by its Chinese name Shan Yao, is a perennial climbing vine in the family Dioscoreaceae native to China and the temperate parts of East Asia, and widely naturalised in eastern North America where it can be invasive. The plant arises from a deeply buried, elongate, club-shaped to cylindrical tuber that may reach a metre or more in length and is the part used as both food and medicine. From the tuber emerges a slender, twining, herbaceous stem that climbs by counter-clockwise rotation to 3 to 5 m. The leaves are opposite (or the upper alternate), distinctively heart-shaped with a deeply cordate base and a long acuminate tip, and bear conspicuous parallel-curving veins. Small white flowers with a faint cinnamon scent are borne in slender spikes from the leaf axils, the species being dioecious. Pea-sized aerial tubers (bulbils) are produced in the leaf axils and are a primary means of vegetative spread.
Active Constituents
Dioscorea polysaccharides (glucomannan-rich)
PolysaccharideConcentration: Major bioactive fraction of the rhizome
Primary active components. Shown in animal models to lower blood glucose, improve insulin sensitivity and lipid metabolism, modulate immunity and beneficially alter gut microbiota.
Diosgenin (steroidal sapogenin)
Steroidal saponin / sapogeninConcentration: Minor in D. opposita relative to industrial Dioscorea spp.
Structurally related to steroid-hormone precursors; possesses anti-inflammatory, hypolipidemic and antioxidant activity. Note: it is not biochemically converted to steroid hormones in the human body.
Allantoin
Purine derivativeConcentration: Present
Cell-proliferative and soothing agent that supports mucosal and wound healing; contributes to the herb's tonifying, Stomach-protecting reputation.
Mucilage and mannan
Polysaccharide / glycoprotein mucilageConcentration: High
Viscous mucilage that coats and soothes the gastrointestinal tract, moderates postprandial glucose absorption and gives the rhizome its characteristic slippery texture.
Amylase (diastase) and other enzymes
Enzyme (protein)Concentration: Present in raw rhizome
Digestive enzymes that may aid starch breakdown, consistent with the traditional Spleen- and Stomach-strengthening use.
Free amino acids and choline
Amino acid / amineConcentration: Present
Contribute nutritive and mild metabolic-supportive properties.
Phytosterols and phytic acid
Sterol / phytateConcentration: Minor
Antioxidant constituents that add to the overall metabolic and cardioprotective profile.
⚠ Drug Interactions
Antidiabetic agents (insulin, sulfonylureas, metformin)
Dioscorea polysaccharides lower blood glucose and improve insulin sensitivity in animal and preliminary clinical studies. Combined with hypoglycemic drugs this could additively reduce blood glucose.
Clinical note: Generally used as a food and gentle tonic; monitor blood glucose if consumed in large medicinal quantities alongside antidiabetic therapy. Evidence is theoretical/pharmacological.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| decoction | 15–30 g | Daily | — | — | 中国药典 2020 【用法与用量】15～30g。 【性味与归经】甘，平。归脾、肺、肾经。 — Chinese Pharmacopoeia 2020, quoted verbatim; route and cautions preserved. Replaces a cleared category-filler value. |
Preparation Methods
Decoction (water extraction)
Parts: Dried rhizome
Commonly 15-30 g (up to 60 g) of dried rhizome decocted in water. Used as a gentle tonic for the Spleen, Lung and Kidney; often combined with other Qi- and Yin-tonifying herbs.
Dry-fried (stir-fried, chao Shan Yao)
Parts: Dried rhizome
Rhizome slices dry-fried (sometimes with bran) to enhance the Spleen-strengthening and diarrhea-stopping action; the raw form is favored for nourishing Yin and generating fluids.
Culinary / powder
Parts: Rhizome
Fresh rhizome cooked as food, or dried rhizome ground to powder and taken with warm water or in congee as a nourishing, easily digested tonic.
Dui Yao — Herb Pairs
The classical two-herb combinations this herb appears in, each with an action neither herb has alone.
The spleen and kidney are strengthened while dampness is resolved and discharge astringed.
Yellow vaginal discharge from spleen deficiency with damp-heat.
Core pair of a classical formula — Yi Huang Tang, Fu Qing Zhu Nü Ke (Fu Shan)
Kidney yin is nourished while spleen qi is tonified, supporting the prenatal through the postnatal.
Core pair of a classical formula — Liu Wei Di Huang Wan, Xiao Er Yao Zheng Zhi Jue (Qian Yi)
Evidence Tier
Strong evidence · 2 studiesRecorded studies by study design, strongest design at the top. This is a study-design tier only, not a GRADE rating: it does not weigh risk of bias, consistency or precision.
Systematic review / meta-analysis
1
1 verified · 0 unverified
Randomized controlled trial
0
Other clinical trial
0
Observational / case report
0
In vitro / animal
1
0 verified · 1 unverified
Other / unclassified
0
Verified: design read from PubMed for a DOI that resolves to the cited paper Unverified: taken from the study's recorded description
Clinical Studies
Additional Benefit of Chinese Medicine Formulae Including Dioscoreae rhizome (Shanyao) for Diabetes Mellitus: Current State of Evidence
Systematic review of 53 randomized controlled trials (~5,000 participants) evaluating herbal formulae containing Shanyao (Dioscoreae rhizome) for diabetes mellitus. Formulae with Shanyao added to conventional therapy showed additional benefit on glycemic indices, with review of underlying experimental mechanisms.
Antidiabetic Effect of Chinese yam (Dioscorea opposita Thunb.) in High-Fat Diet/Streptozotocin-Induced Diabetic Rats
In high-fat-diet/streptozotocin-induced diabetic rats, Chinese yam supplementation improved fasting blood glucose, insulin resistance and lipid parameters, supporting the traditional metabolic-tonifying use of Shan Yao.
Historical Texts
Shennong Bencao Jing (Divine Husbandman's Classic of Materia Medica)
Han dynasty (c. 200 BCE - 200 CE)Bencao Gangmu (Compendium of Materia Medica), Li Shizhen
Ming dynasty, 1578References
- Sun L, Di YM, Lu C, Guo X, Tang X, Zhang AL, Xue CC, Fan G. Additional Benefit of Chinese Medicine Formulae Including Dioscoreae rhizome (Shanyao) for Diabetes Mellitus: Current State of Evidence . Frontiers in Endocrinology (2020) [DOI]
- Bensky D, Clavey S, Stoger E. Chinese Herbal Medicine: Materia Medica, 3rd Edition . Eastland Press (2004) [DOI]
This information is for educational purposes only and is not intended to replace professional medical advice. Always consult a qualified healthcare provider before using any herbal remedy, especially if you are pregnant, nursing, or taking medications.
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