Herb

Du Zhong (Processed)

Eucommia bark salt processed | 盐杜仲

Also known as:

Rubber tree bark , Salt processed Eucommia bark , Yan Zhi Du Zhong

Parts Used

Bark (皮 pí / 树皮 shù pí)

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

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About This Herb

Traditional Chinese Medicine background and properties

Herb Description

Du Zhong (Eucommia bark) is one of the most important herbs in Chinese medicine for strengthening the lower back and knees. It nourishes the Liver and Kidney systems, which govern bones and tendons, making it a go-to remedy for chronic back pain, weak joints, and age-related musculoskeletal decline. It is also used to support healthy pregnancies and has a mild blood-pressure lowering effect.

Herb Category

Main Actions

  • Nourishes Liver and Kidney Yin
  • Strengthens the Sinews and Bones
  • Calms the Fetus
  • Lowers Blood Pressure

How These Actions Work

'Tonifies the Liver and Kidneys' means Dù Zhòng replenishes the Kidney and Liver systems, which in TCM govern the bones and sinews respectively. When these organ systems are depleted, a person may experience chronic low back pain, weak or aching knees, frequent urination, impotence, or dizziness. Du Zhong's warm, sweet nature directly nourishes the Kidney Yang and Liver Blood that sustain the lower body's structural integrity. It is considered a primary herb for Kidney-deficiency type lower back pain, and classical texts describe it as the go-to herb whenever the lumbar region is involved.

'Strengthens sinews and bones' follows directly from its Liver and Kidney tonifying action. Since the Liver governs sinews and the Kidneys govern bones, when these organs are well-nourished, the musculoskeletal framework becomes strong and resilient. This action is applied clinically for weak knees, difficulty walking, stiffness, or conditions where bones and tendons need support, such as recovery from fractures or in degenerative joint conditions.

'Calms the fetus' means Du Zhong stabilizes pregnancy in cases where the mother's Liver and Kidney systems are weak. In TCM, the Kidneys and the Chōng and Rèn vessels are responsible for holding the fetus in place. When these are deficient, symptoms such as lower back aching during pregnancy, vaginal bleeding, or a sensation of the fetus being restless may occur. Du Zhong's tonifying and securing nature addresses this root deficiency. It can be used alone or combined with herbs like Xù Duàn (Teasel root) and Sāng Jì Shēng (Mulberry mistletoe).

'Aids in lowering blood pressure' reflects modern clinical observation. Du Zhong has been shown to have a mild, sustained blood-pressure lowering effect, likely through central mechanisms and vascular relaxation. The salt-processed form and decoctions tend to have stronger effects than tinctures. It is often used as a supporting herb in formulas for hypertension, particularly when high blood pressure accompanies Liver and Kidney deficiency patterns.

Patterns Addressed

In TCM, symptoms cluster into recognizable patterns of disharmony that reveal what's out of balance in the body. Du Zhong is traditionally associated with these specific patterns.

The following describes this herb's classification within Traditional Chinese Medicine theory and is provided for educational purposes only.

Why Du Zhong addresses this pattern

Du Zhong is warm and sweet, entering the Kidney channel directly. Its warmth replenishes Kidney Yang, the fundamental warming and activating force of the body. When Kidney Yang is deficient, the lower back (the 'mansion of the Kidneys') loses its structural support, leading to chronic soreness and cold sensations. Du Zhong's tonifying nature directly addresses this root deficiency, strengthening the lumbar region and restoring the Kidney's ability to govern the bones. Its gentle warmth makes it suitable for long-term use without being overly drying or hot.

A practitioner would look for one or more of these signs

Lower Back Pain

Chronic, dull aching that worsens with fatigue or cold

Frequent Urination

Especially at night, with clear copious urine

Impotence

From Kidney Yang depletion

Knee Pain

Weak, cold, or soft knees

TCM Properties

Temperature

Warm

Taste

Sweet (甘 gān)

Channels Entered
Liver Kidneys
Parts Used

Bark (皮 pí / 树皮 shù pí)

This is partial information on the herb's TCM properties. More detailed information is available on the herb's dedicated page

Product Details

Manufacturing, supplier, and product specifications

Product Type

Granules

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Botanical & Sourcing

Quality Indicators

Good quality Du Zhong bark is thick (ideally 3mm or more), comes in large flat pieces, and has a smooth inner surface of dark purplish-brown colour. The outer rough bark should be cleanly scraped off. The most important quality test: when snapped, the cross-section should reveal abundant, fine, silvery-white rubber threads (jiao si) stretching between the broken edges. More threads indicate better quality and higher lignan/rubber content. The bark should feel slightly moist and dense, not dry or brittle. Aroma is faint; taste is slightly bitter. Salt-processed Du Zhong (yan du zhong) should appear blackish-brown on the surface with reduced thread elasticity and a slightly salty taste.

Primary Growing Regions

Du Zhong is produced primarily in Guizhou, Sichuan, Shaanxi, Hubei, Henan, Yunnan, and Hunan provinces of China. The recognized dao di (terroir) regions are Sichuan and Guizhou, which produce the largest quantities and highest quality, traditionally called 'Chuan Du Zhong' (川杜仲). Material from Shaanxi and Hubei is also well-regarded and commercially known as 'Han Du Zhong' (汉杜仲). The earliest historical producing regions recorded in the Ming Yi Bie Lu include Shangdang (present-day Shanxi) and Hanzhong (present-day southern Shaanxi). Du Zhong is also included in Hunan's 'Xiang Jiu Wei' (湘九味) list of representative provincial herbs.

Harvesting Season

April to June (between Qingming and the Summer Solstice), from trees aged 15–20 years or older. Bark is stripped using a partial-bark method to protect the living tree.

Supplier Information

Treasure of the East

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Miscellaneous Info

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Usage & Safety

How to use this herb and important safety information

Important Medical Disclaimer

The information provided here is for educational purposes only and is not intended as medical advice or to replace consultation with a qualified healthcare professional. This herb is a dietary supplement and has not been evaluated by the FDA. It is not intended to diagnose, treat, cure, or prevent any disease.

Always consult with a qualified healthcare provider, particularly if you are pregnant, nursing, have a medical condition, or are taking other medications. Discontinue use and consult your healthcare provider if you experience any adverse reactions.

Recommended Dosage

Instructions for safe storage and consumption

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Traditional Dosage Reference

Standard

6–15g

Maximum

Up to 20–30g may be used in severe cases of Kidney-deficiency lower back pain or threatened miscarriage, under practitioner supervision. Some historical records describe using up to one liang (approximately 30g) as a single herb, decocted in wine and water.

Notes

Use lower doses (6–10g) as part of a multi-herb tonic formula for general Kidney and Liver supplementation. Use higher doses (10–15g or more) when Du Zhong is a principal herb for acute lower back pain from Kidney deficiency or for stabilizing a threatened pregnancy. The salt-processed form (yan du zhong) is preferred in clinical practice as it better directs the herb's action to the Kidneys and enhances its bone-and-sinew strengthening effects. Stir-frying also breaks down the rubber (gum) matrix, allowing active compounds to dissolve more readily into decoction liquid. Raw (unprocessed) Du Zhong is less commonly used.

Processing Methods

Processing method

The bark is cut into blocks or strips, moistened with salt water (typically 3 parts salt per 100 parts herb, dissolved in boiling water), then stir-fried over gentle heat until the silvery rubber threads snap easily and the surface turns dark brown to charred black.

How it changes properties

Salt processing does not change the temperature significantly but adds a slightly salty taste. The salty flavor directs the herb's action downward into the Kidney channel, strengthening its Kidney-tonifying effect. The frying also destroys the gummy latex (rubber threads), making the active compounds easier to extract during decoction. The result is a warmer, more Kidney-focused herb that is less sticky and more clinically effective in decoction.

When to use this form

Salt-fried Du Zhong is the standard clinical form and is preferred in almost all situations. It is specifically chosen when the treatment goal is Kidney tonification for lower back pain, impotence, frequent urination, or fetal instability. The raw form is rarely used in modern practice because the intact rubber threads make it difficult to extract the active ingredients effectively.

Toxicity Classification

Non-toxic

Du Zhong is classified as non-toxic in both classical texts and the Chinese Pharmacopoeia. The Ming Yi Bie Lu explicitly states it is 'wu du' (无毒, non-toxic). Modern safety testing in rats showed no evidence of acute toxicity at doses up to 1,200 mg/kg of standardized extract given daily for 28 days. The bark's main active components (lignans such as pinoresinol diglucoside, iridoids such as aucubin and geniposidic acid) have favorable safety profiles. No special toxicity concerns or processing-related safety issues exist. The salt-frying (yan chao) processing method is used to direct the herb's action toward the Kidneys and to make it less drying, not for detoxification purposes.

Contraindications

Caution

Yin deficiency with Heat signs (dry throat, irritability, night sweats, hot flashes). Du Zhong is warm in nature and may aggravate Yin-deficient Heat.

Caution

Excess Heat conditions without underlying Kidney or Liver deficiency. As a warming tonic, Du Zhong is inappropriate when pathogenic Heat is the primary issue.

Caution

Threatened miscarriage due to Qi sinking (Qi collapse pattern). Classical texts warn that if the fetus is unstable because Qi is sinking and failing to hold Blood upward, Du Zhong's descending nature may worsen bleeding rather than stabilize the pregnancy.

Caution

Concurrent use with Xuan Shen (Scrophularia root). Classical sources including the Ming Yi Bie Lu record that Du Zhong 'fears' (e, 恶) Xuan Shen, indicating a traditionally recognized incompatibility.

Classical Incompatibilities

Du Zhong does not appear on the Eighteen Incompatibilities (十八反) or Nineteen Mutual Fears (十九畏) lists. However, the Ming Yi Bie Lu records that Du Zhong 'fears' (畏) She Tui Pi (snake shed skin) and 'is averse to' (恶) Xuan Shen (Scrophularia root). These are traditionally recognized incompatibilities outside the main 18/19 lists.

Special Populations

Pregnancy

Du Zhong is traditionally considered safe during pregnancy and is in fact one of the most commonly used herbs for threatened miscarriage (tai dong bu an) due to Kidney deficiency. It calms the fetus and stabilizes the uterus. However, the classical text Ben Cao Qiu Zhen contains an important caution: if fetal instability is caused by Qi sinking rather than Kidney-deficiency Cold, Du Zhong's descending and warming nature could worsen the condition by further drawing Qi and Blood downward. Practitioners therefore must differentiate the pattern carefully. When the cause is Kidney deficiency with Cold, Du Zhong is appropriate and beneficial. When Qi collapse is the primary mechanism, ascending and Qi-lifting herbs should be used instead.

Breastfeeding

No specific classical or modern contraindications exist for Du Zhong during breastfeeding. It is a gentle, non-toxic warming tonic traditionally used in postpartum recovery formulas to strengthen the lower back and replenish Kidney Qi after childbirth. It is generally considered safe at standard doses during lactation. No adverse effects on breast milk or nursing infants have been reported.

Pediatric Use

Du Zhong is generally safe for children at age-appropriate reduced doses, but its warming tonic nature means it is rarely needed in pediatric practice. It may be used for children with Kidney-deficiency patterns presenting as delayed bone development or chronic weakness of the lower limbs. Dosage is typically reduced to one-third to one-half of the adult dose depending on age and body weight. Not commonly prescribed for children under 3 years. As with all tonics in children, course duration should be limited and the child's response monitored.

Drug Interactions

Antihypertensive medications: Du Zhong has demonstrated blood-pressure-lowering effects through multiple mechanisms including nitric oxide modulation and beta-adrenergic blocking activity. Concurrent use with pharmaceutical antihypertensives (ACE inhibitors, ARBs, beta-blockers, calcium channel blockers) could theoretically produce additive hypotensive effects. Blood pressure should be monitored if combining Du Zhong with these medications.

Anticoagulant/antiplatelet drugs: While Du Zhong is not a strong blood-moving herb, some of its bioactive compounds have mild effects on vascular function. Caution is warranted with concurrent warfarin or similar agents, though significant interaction is unlikely at standard doses.

Hypoglycaemic agents: Preliminary research suggests Eucommia extracts may influence blood glucose levels. People taking insulin or oral hypoglycaemics should be aware of potential additive effects, though robust clinical evidence of significant interaction is lacking.

Dietary Advice

As a warming Kidney and Liver tonic, Du Zhong works best when supported by a warm, easily digestible diet. Avoid excessive cold or raw foods (salads, chilled drinks, raw seafood) while taking Du Zhong, as these can impair Spleen and Kidney Yang function and counteract the herb's warming therapeutic effects. Foods that support the Kidneys, such as black sesame, walnuts, bone broth, and lamb, complement Du Zhong's actions well. Du Zhong is traditionally decocted with wine for enhanced circulation to the lower back and legs.

Cautions & Warnings

Although this herb is typically safe for most individuals, it may cause side effects in some people. Pregnant women, nursing mothers, postpartum women, and those with liver disease should use the formula with caution.

As with any Chinese herbal remedy, it is advisable to seek guidance from a qualified TCM practitioner before beginning treatment.