Bai Zhu’s Pao Zhi Choices
By Eric Brand
Bai Zhu is one of the most commonly used items in the Chinese materia medica. One local herb company puts Bai Zhu at the #10 slot in terms of total herb sales, and import data from Taiwan shows that Bai Zhu was ranked #9 in total volume with just over 488,000 kg imported in 1997. Clearly, Bai Zhu is one of the most important herbs in Chinese medicine, but many Western practitioners remain uncertain as to which processing method is best for any given patient.
When I was going to school for Chinese medicine in California, I did an apprenticeship with an old Chinese-Vietnamese herbalist in a Chinatown-style herb shop. I remember that every time we opened a box of Bai Zhu, he would routinely put half of it in the toaster oven to make “Chao Bai Zhu.” Technically, a toaster oven isn’t the traditional tool for chao-processing, which refers to stir-frying in a dry wok; however, the toaster oven is very convenient and widely-used in the modern day herb shop. The Bai Zhu is baked until it becomes aromatic and changes to a yellowish-brown color, which is the same basic effect that the dry wok achieves. Traditionally, Bai Zhu is also often stir-fried with bran or earth (Zao Xin Tu).
All day long I would watch students drop off their prescriptions at the shop, and all day long the boss would shake his head when he looked at the prescriptions. The prescriptions invariably just said Bai Zhu with no mention of the pao zhi method, and the old boss would never fail to comment on how we gringos don’t understand Chinese herbs. For his own patients, a prescription would never come through without specifying the pao zhi method of something like Bai Zhu, and over the years I’ve noticed that many of the best herbalists I see always pay attention to pao zhi. Yet years later, I look at the disparity between Chao Bai Zhu vs. Sheng Bai Zhu sales and I know that most people are using it without attention to pao zhi. Based on their indications and the prevalence of different clinical patterns, Chao Bai Zhu should be way ahead of raw Bai Zhu, but the opposite is true.
Bai Zhu is principally used in clinic for the following actions: supplementing qì and fortifying the spleen, drying dampness and disinhibiting water, checking sweating, and quieting the fetus. Bai Zhu and Cang Zhu were originally used interchangeably (they were regarded as one medicinal in ancient times), and they share a common feature- both items have a drying nature. Traditionally, the drying nature of Bai Zhu was thought to be moderated by stir-frying. From the modern perspective, people believe that the drying nature of Bai Zhu is related to its essential oil content; stir-frying reduces the essential oil content, reducing irritation in the stomach and intestines from a biomedical perspective while aromatically fortifying the spleen and opening the stomach from a traditional perspective.
Sheng Bai Zhu, the unprocessed form, is preferred for drying dampness, disinhibiting water and dispersing swelling. It is used for edema (water swelling), phlegm-rheum, and wind-damp impediment pain.
Tu Bai Zhu, the earth-processed form, is made by stir-frying Bai Zhu with Zao Xin Tu. 20 kg of Zao Xin Tu (oven earth, Terra Flava Usta) are used for every 100 kg of Bai Zhu; the Zao Xin Tu is first heated, then the sliced Bai Zhu is added. The Zao Xin Tu is then sieved off, leaving the sliced roots a slightly brown-yellow color. This form is best for checking diarrhea, and is used for spleen vacuity with low food intake, diarrhea, and sloppy stool.
Chao Bai Zhu, the normal stir-fried form, is typically processed by using 10 kg of honey-processed bran for every 100 kg of Bai Zhu. However, it is not uncommon for people to simply stir-fry the Bai Zhu on its own until it becomes aromatic and changes color to a yellowish-brown color. This method moderates the drying nature and is best for fortifying the spleen. It is used for disharmony of the spleen and stomach with poor movement and transformation, reduced food intake, distention and fullness, fatigue and lack of strength, exterior vacuity with spontaneous sweating, and restless fetus.
The methods of stir-frying till yellow and stir-frying with earth have been in use since the Tang dynasty; these methods are documented in the texts Qian Jin Yi Fang (“Wings of the Thousand Gold Pieces Formulary”) and Wai Tai Mi Yao (“Essential Secrets from Outside the Metropolis”). Stir-frying with bran came slightly later; it dates back to the Song dynasty, which started around 1000 years ago. The essential oil content is reduced by about 15% when the item is stir-fried.
Source texts for pao zhi info:
百藥炮製, Processing of One Hundred Medicinals, Zhao Zhongzhen. Hong Kong, 2010.
中藥炮製學, Chinese Medicinal Processing, Ye Dingjiang. Taipei, 2002.