Common Yam Rhizome
Naming
Shan Yao (Rhizoma Dioscoreae)——Shen Nong Ben Cao Jing (Shen Nong’s Herbal)
Origin
The rhizome of the perennial herbaceous trailing plant Dioscorea opposita Thunb. of the family Diosoreaceae.
Location
Mainly produced in Henan. It is excellent which produced in Henan, called Huai Shan Yao. Also produced in Hebei and Shaanxi provinces in China.
Harvest
Plucked in winter after stalk and leaves withered.
The actual smell and taste
Slight flavor, slightly sour.
Best quality
Coarse, firm, rich powder, spotlessly white, white cross section, sticky while chewed.
Processing
Sliced thickly, unprocessed, or stir-baked with bran.
Property
Sweet, neutral; spleen, lung and kidney meridians entered.
Actions
Tonify qi, nourish yin, and tonify spleen, lung and kidney.
Indications
A. Spleen qi deficiency syndromes
It is indicated for poor appetite with loose stool, diarrhea due to spleen qi deficiency, especially for both spleen qi and yin deficiency, or needing tonifying but failure in transportation of spleen due to weakness after illness, because it can tonify both qi and yin of spleen, and it is astringent in property. For dual usage of food and medicine, neither dry nor greasy in property, it is applied singly, or taken as food for long term. For serious cases of qi deficiency, it is commonly combined with qi and spleen tonics, because it is mild in action. For instance, it is used with Ren Shen and Bai Zhu in Shen Ling Bai Zhu San from Tai Ping Hui Min He Ji Ju Fang for poor appetite with loose stool, and in Wan Dai Tang from Fu Qing Zhu Nv Ke for leukorrhagia due to down-pour of damp-turbid caused by spleen deficiency and failure in transportation.
B. Lung qi deficiency syndromes
It can tonify both qi and yin of lung directly, and tonify metal (lung) through tonify earth (spleen). For cough with little sputum or no sputum, shortness of breath, and spontaneous sweating due to lung qi and yin deficiency, it is commonly combined with herbs of tonifying qi, nourishing yin, moistening lung, relieving cough. For instance, it is used with Dang Shen, Mai Dong and Bai He. It is indicated for cough and dyspnea due to qi and yin deficiency of lung and kidney, because it can tonify qi, and nourish lung and kidney. It is usually combined with herbs of tonifying kidney, astringing lung, receiving qi and relieving dyspnea. For instance, it is used with Shu Di Huang, Shan Zhu Yu and Wu Wei Zi in Qi Wei Du Qi Wan from Zhang Shi Yi Tong (Zhang’s Medical Experience Collection).
C. Kidney deficiency syndromes
It is indicated for deficiency of yin, yang and essential qi of kidney, because it can tonify kidney qi and yin, and also has the action of astringing. It is occurred in many famous formula of kidney tonifying and combined with kidney tonics and astringents. It is indicated for soreness and weakness of lumbar and knees, frequent urination, enuresis, seminal emission, premature ejaculation, leukorrhagia in thin quality due to kidney qi deficiency, emaciated, soreness and limpness of lumbar and knees, seminal emission due to kidney yin deficiency, for instance, it is used in Liu Wei Di Huang Wan from Xiao Er Yao Zheng Zhi Jue, which is famous for tonifying kidney yin, and in Shen Qi Wan from Jin Kui Yao Lue, which is famous for tonifying kidney yang.
D. For diabetes due to both qi and yin deficiency
It is indicated for diabetes due to both qi and yin deficiency, because it can tonify both qi of spleen, lung and kidney, and yin of spleen, lung and kidney. For diabetes in slight degree, it is decocted singly and taken instead of tea. For diabetes in serious degree, it is combined with herbs of tonifying qi, nourishing yin, clearing heat, producing fluid. For instance, it is used with Huang Qi, Tian Hua Fen and Zhi Mu in Yu Ye Tang from Yi Xue Zhong Zhong Can Xi Lu.
Dosage and Administrations
Decoct 5~30 g, 60~250 g in large dosage, stir-baked with bran for enhancing action of spleen tonifying and diarrhea relieving.