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Dioscorea (shan yao)

What is dioscorea? What is it used for?

Also known as the Chinese yam, dioscorea has been utilized in traditional Chinese medicine for centuries. Although there are approximately 800 different species of dioscorea, the Chinese yam is native to China, Japan, Korea and Taiwan.

The plant consists of a climbing vine studded with heart-shaped leaves and small, white flowers that smell like cinnamon. The yam consists of the plant's root, which is thick, spindle-shaped and white on the inside. The yams are harvested in the winter; after the outer bark is removed, the root is washed and allowed to dry in the sun, then rehydrated and cut into thick slices.

Chinese yam is classified as neutral and sweet. It is used as a tonic and serves to tonify the spleen and stomach; augment the lung yin and tonify lung qi; and stabilize and tonify the kidneys.

Chinese yam contains large amounts of mucilage, which soothe the mucus membranes and can help relieve cough. It is also taken to treat poor digestion; fatigue and diarrhea; weakness; frequent urination; decreased appetite; and wheezing.

Chinese yam is often combined with other herbs as part of larger formulas. For instance, it is sometimes combined with poria and white atractylodes for loose stools, and with codonopsis root for general weakness and fatigue.

How much dioscorea should I take?

The general dosage of dioscorea is 10-30 grams of root or 6-10 grams of powder. A tea may also be prepared by steeping slices of Chinese yam into boiling water.

What forms of dioscorea are available?

Whole, dried slices of Chinese yam are readily available, as are Chinese yam powders and extracts.

What can happen if I take too much dioscorea? Are there any interactions I should be aware of? What precautions should I take?

Overdosing of Chinese yam may be potentially poisonous because one of the root's compounds, dioscorin, may have a toxic effect on the body. Chinese yam should not be taken by women who are pregnant or breastfeeding; it should also not be taken if a patient's symptoms include abdominal pain and swelling. In addition, it should not be taken with the herb kan sui. As of this writing, there are no known drug interactions with Chinese yam.

As always, consult with a qualified, licensed health care provider before taking dioscorea or any other herbal remedy or dietary supplement.


  • British Herbal Pharmacopoeia, fourth edition. Great Britain: Biddles Ltd., Guildford and King's Lynn, 1996, p. 187.
  • Dioscorea. Gale Encyclopedia of Alternative Medicine. Gale Group, 2001.
  • Duke JA. The Green Pharmacy. New York: St. Martin's Press, 1997, pp. 209-210.
  • Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines. Montvale, NJ: Medical Economics Company, 1998, pp. 809-810.
  • Teeguarden R. Radiant Health: The Ancient Wisdom of the Chinese Tonic Herbs. New York: Warner Books, 1998, pp. 186-187.
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