Chinese Name : 山药
Latin Name : Rizoma Dioscoreae
This herb is the rhizome of Dioscorea appasita Thumb. of the family Dioscoreaceae. The chinese yam, grown in the Henan province (Xinxiang county) is believed to be the best variety, although Chinese yams found in other provinces (including Hebei, Shandong, and Shanxi in the northern, southern, and southwestern provinces) are equally effective. Harvested in the winter, it is cleaned, skinned, smoked with sulfur, and dried, or further processed with wheat bran and sliced.
Chinese yam is a tonic and restorative herb. It benefits the spirit, promotes growth, and, when taken habitually, brightens the intellect, promotes flesh (helps build new muscle and tissue), and prolongs life. Unprocessed yam is good for nourishing Qi and kidney yin, and production of body fluids. It is commonly used to treat diabetes and bronchitis. Stir-baked yam with wheat bran is good for invigorating the spleen, stopping diarrhea, and nourishing the kidneys for strength and vitality. Chinese yam is also an antiaging medicinal herb.
Use of Chinese Yam in TCM
Sweet in taste and neutral, it acts on the spleen, lung, and kidney meridians.
Effects, Medicinal Uses and Combinations
- Nourishes the Stomach and Spleen:
- For metabolic imbalance, diminished functioning of the spleen, and diabetes, Chinese yam is often used with astragalus, trichosanthes root, codonopsis, and hoelen, as in Yu Quan Wan (R-12).
- For poor appetite, lassitude, loose stools, and diarrhea, Chinese yam is blended with ginseng, prepared licorice root, white atractylodes rhizome, and poria, as in Shen Ling Bai Zhu San (R-13).
- Strengthens kidney yin: for weakness and soreness in the waist and knees, vertigo, tinnitus, deafness, night sweating, frequent urination, leukorrhea, or spermatorrhea due to deficiency of the kidney yin, Chinese yam is mixed processed rehmannia root, cornus fruit, alisma, moutan, and hoelen, as in Liu Wei Di Huang Wan (R-22)
- Nourishes the lungs and promotes production of body fluids: for a cough and dyspnea due to lung deficiency, Chinese yam is combined with codonopsis root, ophiopogon root, and schisandra fruit.
- Invigorating Kidney-Qi:
- To treat deficiency of Kidney-Qi and kidney yang, Chinese yam is dispensed with dried rehmannia, poria, cinnamon twig, cornus, and alisma, as in Jin Gui Shen Qi Wan or Shen Qi Wan (R-24).
- To treat profuse leukorrhea due to Dampness and deficiency of Kidney-Qi and Spleen-Qi, chinese yam is prescribed with codonopsis root, white atractylodes rhizome, and plantain seed. Chinese yam is used with phellodendron bark (huang bai) if yellow leukorrhea with signs of Damp-Heat is diagnosed.
- Nourishes both Qi and yin: can be used in a recipe for treating anguish with thirst, smothering sensations (confused and suppressed state), and other symtomps of diabetes; Chinese yam can be given daily with astragalus root, pueraria root, trichosanthes root, ophiopogon, dry rehmannia, and anemarrhena rhizome (zhi mu) in decoction known as Yu Ye Tang.
A decoction of 10 to 30 g, or 6 to 10 g in powdered form is taken orally with water. Doses up to 60 to 250 g per day can be administered.
People with Damp-Heat diarrhea should avoid Chinese yam. Those with spleen-yin-deficient-type diarrhea with stagnation in the abdomen should avoid Chinese yam. To avoid detroying the enzyme when making a decoction do not overcook. Avoid cooking Chinese yam with drugs or foods that are alkaline in nature.
Side Effects and Toxicity
At the normal dosage, no adverse reactions have been reported.
Chinese yam contains 2 percent sapponins (sapogenin) phenolic compounds, namely cholin and batatasins I-V, other ingredients are: glycosides, starch, enzymes, arginin, mannan, phytic acid, arginine, phytic acid, allantoin, and vitamin C.
- The enzymes content in Chinese yam lowers blood sugar levels in diabetics.
- It nourishes the body and improves appetite. The protein content in Chinese yam furnishes essential amino acids; it is particularly good for those who lack appetite, and the elderly.