Herb Seed (种子 zhǒng zǐ / 子 zǐ / 仁 rén)

Dao Dou

Sword Bean · 刀豆

Canavalia gladiata (Jacq.) DC. · Semen Canavaliae

Also known as: Jack Bean

Dao Dou (Sword Bean) plant

Images shown are for educational purposes only

Sword bean seed is a gentle warming herb used primarily for persistent hiccups, nausea, and vomiting caused by cold in the digestive system. It is also used to support the kidneys and relieve lower back pain from kidney weakness. Think of it as a warming digestive aid that helps redirect upward-moving discomfort back downward.

Category Qi-regulating herbs (理气药)
Therapeutic focus Digestive Health Hiccup Relief Lower Back and Knee Health Kidney Health

TCM Properties

Temperature

Warm

Taste

Sweet (甘 gān)

Channels entered

Stomach, Kidneys

Parts used

Seed (种子 zhǒng zǐ / 子 zǐ / 仁 rén)

Educational content • Consult qualified TCM practitioners for diagnosis and treatment

What This Herb Does

Every herb has a specific set of actions — here's what Dao Dou does in the body, explained in both everyday and TCM terms

Therapeutic focus

In practical terms, Dao Dou is primarily used to support these areas of health:

Digestive Health Hiccup Relief Lower Back and Knee Health Kidney Health

TCM Actions

In TCM terminology, these are the specific therapeutic actions that Dao Dou performs to restore balance in the body:

Warms the Middle Burner Descends Qi Directs Rebellious Qi Downward and Stops Hiccup Tonifies Kidney Yang Protects the Stomach

How these actions work

'Warms the Middle Burner' means Dao Dou warms the Stomach and Spleen when they are affected by cold. In TCM, the 'Middle Burner' refers to the digestive organs. When the Middle Burner is too cold, it can cause nausea, vomiting, bloating, and poor digestion. Dao Dou's warm and sweet nature gently warms this area, restoring normal digestive function. This is its most commonly used action.

'Directs Qi downward and stops hiccup' is the hallmark action of this herb. In TCM, hiccup (called 'rebellious Stomach Qi') happens when Qi moves upward instead of downward through the digestive system. Dao Dou has a descending nature that redirects this upward-rushing Qi back downward. It is particularly suited for persistent hiccups caused by cold and deficiency in the Stomach, not for hiccups caused by excess heat. The classical text Ben Cao Gang Mu specifically noted its ability to stop severe post-illness hiccups by helping Qi descend and return to its root.

'Tonifies the Kidney and assists Yang' means Dao Dou can gently warm and strengthen the Kidney's warming function (Kidney Yang). The Kidneys in TCM govern the lower back, bones, and reproductive vitality. When Kidney Yang is weak, symptoms like lower back pain, cold limbs, and fatigue can occur. Because Dao Dou enters the Kidney channel, it can be used to support Kidney Yang, particularly for lower back pain due to Kidney deficiency.

Patterns Addressed

In TCM, symptoms cluster into recognizable patterns of disharmony. Dao Dou is used to help correct these specific patterns.

Why Dao Dou addresses this pattern

Dao Dou is sweet and warm, entering the Stomach channel directly. Its warm nature counteracts the cold that impairs the Spleen and Stomach's digestive and transformative functions. Its descending quality specifically addresses the upward rebelliousness of Stomach Qi that occurs when the Middle Burner is cold and weak, manifesting as hiccups, belching, nausea, and vomiting. The sweet taste tonifies and harmonizes the Stomach and Spleen, while the warmth dispels the cold that is the root of this pattern.

A practitioner would look for one or more of these signs

Hiccups

Persistent hiccups from cold in the Stomach, often worse after cold food or drink

Nausea Or Vomiting

Vomiting of clear fluid due to Stomach cold

Post-Surgical Constipation And Bloating

Abdominal bloating and fullness with preference for warmth

Poor Appetite

Reduced appetite with bland taste in the mouth

Commonly Used For

These are conditions where Dao Dou is frequently used — but only when they arise from the specific patterns it addresses, not in all cases

Arises from: Spleen and Stomach Qi Deficiency

TCM Interpretation

In TCM, hiccups are understood as 'rebellious Stomach Qi' (胃气上逆), meaning the Qi of the Stomach is flowing upward instead of in its normal downward direction. This can be triggered by several causes, but when it is due to cold and deficiency in the Middle Burner, the Stomach loses its ability to properly direct Qi downward. Cold congeals and obstructs, disrupting the smooth flow of Qi through the digestive system. The result is spasmodic, persistent hiccups that may be accompanied by a cold sensation in the stomach area, a preference for warm drinks, and a pale tongue.

Why Dao Dou Helps

Dao Dou directly addresses cold-type hiccups through two complementary mechanisms. First, its warm nature dispels the cold that has accumulated in the Stomach, removing the root obstruction that causes Qi to rebel upward. Second, its descending quality actively redirects Stomach Qi back downward, restoring the normal direction of digestive flow. The Ben Cao Gang Mu specifically documented a case of severe post-illness hiccups that was cured by Dao Dou, explaining the mechanism as 'directing Qi downward and returning it to its root' (下气归元). For chronic or stubborn hiccups, it is often combined with other descending herbs like Ding Xiang (clove) and Shi Di (persimmon calyx) to strengthen the effect.

Also commonly used for

Nausea Or Vomiting

Vomiting from Stomach cold

Post-Surgical Constipation And Bloating

Abdominal distension and fullness from cold obstruction

Sinusitis

Used traditionally as a powder taken with wine

Whooping Cough

Classical folk remedy combined with licorice and rock sugar

Dysentery

Chronic dysentery from Spleen and Stomach cold

Herb Properties

Every herb has an inherent temperature, taste, and affinity for specific channels — these properties determine how it interacts with the body

Temperature

Warm

Taste

Sweet (甘 gān)

Channels Entered

Stomach Kidneys

Parts Used

Seed (种子 zhǒng zǐ / 子 zǐ / 仁 rén)

Dosage & Preparation

These are general dosage guidelines for Dao Dou — always follow your practitioner's recommendation, as dosages vary based on the formula and your individual condition

Standard dosage

6-9g

Maximum dosage

Up to 15g in decoction for stubborn hiccups or significant Kidney deficiency lumbar pain, under practitioner supervision.

Dosage notes

The standard decoction dose is 6 to 9g. For persistent hiccups (the herb's most celebrated use), the classical method involves charring the seeds to ash (shao cun xing), grinding to powder, and taking 6g dissolved in warm water or with rice wine. This powdered form is considered more effective for acute hiccups than standard decoction. For Kidney deficiency lumbar pain, 2 seeds can be wrapped inside a pig kidney and roasted until done, then eaten as a medicinal food. When used for whooping cough, 10 seeds (crushed) are decocted with Gan Cao and rock sugar.

Preparation

When used in decoction, the hard seeds should be crushed before adding to the pot to allow proper extraction. For the classical hiccup remedy, seeds are charred (shao cun xing, 烧存性) until carbonized but retaining their medicinal properties, then ground to fine powder and taken dissolved in warm water or rice wine rather than decocted.

Processing Methods

In TCM, the same herb can be prepared in different ways to change its effects — here's how processing alters what Dao Dou does

Processing method

The seeds are roasted until charred on the outside but retain their inner properties (烧存性), then ground into a fine powder.

How it changes properties

Charring concentrates and enhances the herb's Qi-descending and warming properties. The charred form is considered more potent for stopping hiccups and has a mildly astringent quality that may help with chronic conditions. The thermal nature remains warm.

When to use this form

Used specifically for severe, persistent hiccups that do not respond to milder approaches. The Ben Cao Gang Mu records this form taken as a powder with warm water or wine for intractable post-illness hiccups.

Common Herb Pairs

These ingredients are traditionally combined with Dao Dou for enhanced therapeutic effect

Ding Xiang
Ding Xiang 1:1 (Ding Xiang 3-6g : Dao Dou 6-9g)

Both herbs warm the Middle Burner and direct Qi downward, but they do so through complementary mechanisms. Ding Xiang (clove) is strongly aromatic and warming, powerfully warming the Stomach and descending rebellious Qi. Dao Dou adds gentle Kidney-supporting warmth and reinforces the descending action. Together, they create a stronger effect for stopping hiccups and vomiting from Middle Burner cold than either herb alone.

When to use: Persistent hiccups or vomiting due to cold deficiency of the Spleen and Stomach, especially when symptoms are stubborn and unresponsive to milder treatments.

Shi Di
Shi Di 1:1 (Shi Di 6-9g : Dao Dou 6-9g)

Shi Di (persimmon calyx) is a classic herb for stopping hiccups by descending Stomach Qi. When combined with Dao Dou, the pair addresses both the symptom (rebellious Qi) and the underlying cause (Stomach cold). Shi Di focuses on the descending function while Dao Dou adds warming support, making the combination more effective for cold-type hiccups than either herb used alone.

When to use: Hiccups and belching due to cold in the Stomach, particularly when the hiccups are loud and persistent.

Sheng Jiang
Sheng Jiang Sheng Jiang 6-9g : Dao Dou 6-9g

Sheng Jiang (fresh ginger) warms the Stomach, disperses cold, and stops vomiting. Combined with Dao Dou, the pair provides layered warming of the Middle Burner: Sheng Jiang disperses acute cold while Dao Dou provides deeper warming and Qi-descending action. The combination is particularly effective for vomiting and nausea from Stomach cold.

When to use: Nausea and vomiting from cold in the Stomach, especially when accompanied by a cold sensation in the epigastric region and clear watery vomitus.

Comparable Ingredients

These ingredients have overlapping uses — here's how to tell them apart

Shi Di
Dao Dou vs Shi Di

Both herbs descend Stomach Qi and stop hiccups, but they differ in thermal nature and breadth of action. Shi Di (persimmon calyx) is neutral in temperature and is the single most commonly used herb specifically for hiccups of any type (hot or cold). Dao Dou is warm and only suited for cold-type hiccups, but it has the added benefit of warming the Middle Burner and tonifying Kidney Yang. Choose Shi Di when the hiccup pattern is unclear or involves heat; choose Dao Dou when cold deficiency is clearly the underlying cause.

Ding Xiang
Dao Dou vs Ding Xiang

Both herbs warm the Middle Burner and descend Qi, but Ding Xiang (clove) is significantly more potent and aromatic, with a stronger warming action that also warms the Kidneys and relieves pain. Ding Xiang is classified as a warm-interior herb rather than a Qi-regulating herb. Dao Dou is milder and gentler, making it better suited for patients who need only light warming or who cannot tolerate stronger warming herbs. Ding Xiang is the first choice for severe cold-type hiccups; Dao Dou is used in milder cases or as a supportive herb.

Identity & Adulterants

Related species and common adulterations to be aware of when sourcing Dao Dou

Dao Dou (Canavalia gladiata) is sometimes confused with or substituted by the closely related Yang Dao Dou (洋刀豆, Canavalia ensiformis, Jack Bean). The two species are very similar in appearance and have overlapping medicinal uses in some regions (notably Sichuan). The key distinction: Dao Dou (C. gladiata) is a climbing/twining vine, and its seeds have a long hilum (seed scar) that is approximately three-quarters of the seed's circumference. Yang Dao Dou (C. ensiformis) is a more upright, bushy plant, with shorter pods (about 10 cm) and a hilum that is only about half the seed's length. C. ensiformis contains higher levels of canavanine and other antinutritional factors, so correct identification matters.

Educational content — always consult a qualified healthcare provider or TCM practitioner before using any herb.

Toxicity Classification

Classical Chinese pharmacopoeia toxicity rating for Dao Dou

Non-toxic

While classified as non-toxic in the Chinese Pharmacopoeia when properly processed for medicinal use, raw or undercooked Dao Dou seeds contain several antinutritional and potentially harmful substances: concanavalin A (a lectin/hemagglutinin), canavanine (a non-protein amino acid), urease, and trypsin inhibitors. These compounds can irritate the gastrointestinal lining and cause nausea, vomiting, abdominal pain, diarrhea, and dizziness if ingested without adequate cooking. Proper processing, whether by thorough boiling, charring (shao cun xing), or dry-roasting, effectively neutralizes these substances and renders the herb safe for consumption. When used as a decoction at standard dosages (6 to 9g), the boiling process during preparation is sufficient to denature the lectins and deactivate canavanine.

Contraindications

Situations where Dao Dou should not be used or requires extra caution

Caution

Stomach Heat (胃热) patterns: Dao Dou is warm in nature and designed to treat cold-type conditions. Those with Stomach Heat, manifesting as burning epigastric pain, excessive appetite, bad breath, or acid reflux, should avoid this herb as it can worsen Heat symptoms.

Caution

Yin deficiency with Heat signs: People with dry mouth, night sweats, hot flashes, or other signs of Yin deficiency with internal Heat should use this herb cautiously, as its warming nature may further deplete Yin fluids.

Avoid

Raw or undercooked consumption: Dao Dou seeds contain lectins (concanavalin A), canavanine, and other antinutritional substances that can cause nausea, vomiting, abdominal pain, and dizziness if consumed raw or insufficiently cooked. Seeds must always be thoroughly processed before use.

Caution

High potassium levels or use of potassium-sparing medications: Dao Dou has a relatively high potassium content. People with hyperkalemia or those taking potassium supplements or potassium-sparing drugs should exercise caution.

Special Populations

Important considerations for pregnancy, breastfeeding, and pediatric use

Pregnancy

No specific pregnancy contraindication is recorded in classical or modern Chinese materia medica sources for Dao Dou. However, as a warming herb that directs Qi downward, it should be used with caution during pregnancy. The seeds contain canavanine, a non-protein amino acid, and early animal studies have raised theoretical concerns about potential effects on reproduction, though human data are lacking. Pregnant individuals should consult a qualified practitioner before use and avoid raw or undercooked preparations.

Breastfeeding

No specific warnings regarding breastfeeding are recorded in classical or standard modern Chinese materia medica references for Dao Dou. At standard medicinal doses in properly prepared decoctions, it is generally considered compatible with breastfeeding. However, the seeds contain lectins and canavanine, and there is no formal safety data on transfer through breast milk. Nursing mothers should use it only under practitioner guidance and ensure it is thoroughly cooked or processed.

Children

Dao Dou has been used traditionally for children, particularly for pediatric hernia (xiao er shan qi) and whooping cough. For hernia, classical formulas call for Dao Dou seed powder at approximately 4.5g (one and a half qian), taken with warm water. For whooping cough, 10 seeds (crushed) are decocted with Gan Cao and rock sugar. Dosages for children should be reduced proportionally based on age and body weight, under practitioner supervision. As with adults, seeds must be thoroughly cooked or processed before any preparation for children.

Drug Interactions

If you are taking pharmaceutical medications, be aware of these potential interactions with Dao Dou

No well-documented pharmaceutical drug interactions specific to Dao Dou have been established in clinical literature. However, based on its known chemical constituents, the following theoretical considerations apply:

  • Potassium-sparing drugs and potassium supplements: Dao Dou has relatively high potassium content. Concurrent use with potassium-sparing diuretics (e.g. spironolactone), ACE inhibitors, or potassium supplements may theoretically increase the risk of hyperkalemia.
  • Immunosuppressants: Concanavalin A (ConA), a lectin present in the seeds, is a known T-cell mitogen and immunostimulant in laboratory settings. Although cooking and processing largely denature this protein, people on immunosuppressive therapy should exercise caution.
  • Anticoagulants: Lectins in raw or underprocessed seeds can affect blood cell agglutination. This is unlikely to be clinically relevant with properly prepared decoctions, but caution is warranted for those on anticoagulant therapy.

Dietary Advice

Foods and dietary considerations when taking Dao Dou

While taking Dao Dou for cold-type Stomach or Kidney conditions, avoid cold, raw, and chilled foods and beverages, which can counteract its warming effect. Warm, easily digestible foods such as congee and cooked vegetables support the herb's therapeutic actions. If using Dao Dou to address hiccups, avoid spicy, greasy, or irritating foods that may aggravate Stomach Qi rebellion.

Botanical Description

Physical characteristics and morphology of the Dao Dou source plant

Canavalia gladiata (Jacq.) DC. is a vigorous, climbing herbaceous vine in the Fabaceae (legume) family that can grow several meters long. It has trifoliate compound leaves with ovate leaflets that are slightly larger than those of the common cowpea. The plant flowers from July to September, producing butterfly-shaped purple or pinkish-white flowers arranged in racemes. The fruit pods are distinctive and striking: long, straight, slightly curved sword-shaped legumes measuring 20 to 40 cm in length, with a flattened shape and a pronounced dorsal ridge, somewhat resembling a large blade or scimitar, hence the Chinese name Dao Dou ("knife bean" or "sword bean"). Each pod contains 8 to 16 seeds.

The medicinal part consists of the dried mature seeds, which are flat kidney-shaped or broadly oval, 2 to 3.5 cm long, with a smooth, slightly wrinkled surface that is pale red to reddish-purple in colour. A prominent crescent-shaped black hilum (seed scar) runs along the edge, approximately three-quarters of the seed's circumference. The plant prefers warm, tropical to subtropical climates and is not frost-tolerant, growing best at temperatures between 20 and 30°C.

Sourcing & Harvesting

Where Dao Dou is sourced, when it's harvested or collected, and how to assess quality

Harvesting season

Autumn, when the seeds are fully mature. The ripe pods are collected, sun-dried, and the seeds are removed.

Primary growing regions

Dao Dou is cultivated throughout China's Yangtze River basin and southward, with the largest production in the South China provinces (Guangdong, Guangxi, Yunnan, Fujian, Sichuan, and Jiangxi). It is also grown in Beijing and other temperate regions on a smaller scale. The plant originally comes from tropical Asia and is widely distributed across tropical and subtropical regions of Asia and Africa. In China, the herb from the southern provinces, particularly Guangdong and Yunnan, is considered standard quality. There is no single dominant dao di (terroir) region for this herb, as it is broadly cultivated rather than wild-harvested from a specific locale.

Quality indicators

Good quality Dao Dou seeds are flat kidney-shaped (reniform) or broadly oval, 2 to 3.5 cm long, 1 to 2 cm wide, and 0.5 to 1.2 cm thick. The surface should be pale red to reddish-purple, slightly wrinkled, with a subtle glossy sheen. A prominent crescent-shaped black hilum (seed scar) approximately 2 cm long should be visible along the edge, with three fine white lines running across it. The seed coat should be leathery and hard, with a brownish-green, shiny inner surface. When split open, the two cotyledons should be yellowish-white and appear oily or moist. The herb should have little odour and a bland taste with a slight bean-like flavour when chewed. Avoid seeds that are mouldy, insect-eaten, shrivelled, or dull in colour.

Classical Texts

Key passages from the classical Chinese medical texts that describe Dao Dou and its therapeutic uses

《本草纲目》(Ben Cao Gang Mu) by Li Shizhen, Ming Dynasty

Original: 刀豆，本草失载，惟近时小书载其暖而补元阳也。又有人病后呃逆不止，声闻邻家。或令取刀豆子烧存性，白汤调服二钱，即止。此亦取其下气归元，而逆自止也。

Translation: Dao Dou was not recorded in earlier materia medica. Only recent minor texts record that it warms and supplements the original Yang. There was a person who, after illness, had incessant hiccups so loud they could be heard by the neighbours. Someone advised him to take Dao Dou seeds, char them to ash (retaining their properties), and take two qian mixed with plain hot water, and they stopped immediately. This also works by directing Qi downward and returning it to its origin, so the rebellious [Qi] naturally ceases.

《本草纲目》(Ben Cao Gang Mu) — Properties Section

Original: 甘，平，无毒。温中下气，利肠胃，止呃逆，益肾补元。

Translation: Sweet, neutral, non-toxic. Warms the middle, directs Qi downward, benefits the intestines and Stomach, stops hiccups, tonifies the Kidneys, and supplements the original [Qi].

《滇南本草》(Dian Nan Ben Cao) by Lan Mao, Ming Dynasty

Original: 健脾。

Translation: Strengthens the Spleen.

《本草从新》(Ben Cao Cong Xin) by Wu Yiluo, Qing Dynasty

Original: 味甘温。入手足阳明经。功专温中下气，利肠胃，益肾归元。取子烧存性，白汤调下，治呃逆神效。

Translation: Sweet and warm in flavour. Enters the Hand and Foot Yangming channels. Its principal function is warming the middle and directing Qi downward, benefiting the intestines and Stomach, tonifying the Kidneys and returning [Qi] to its origin. Char the seeds to ash, mix with plain water and take. This is miraculously effective for hiccups.

Historical Context

The history and evolution of Dao Dou's use in Chinese medicine over the centuries

Dao Dou, meaning "knife bean" or "sword bean," gets its name from the shape of its long, flat pods, which resemble a sword or a large curved blade. The earliest known mention of the plant by a similar name appears in the Tang Dynasty text You Yang Za Zu (酉阳杂俎) by Duan Chengshi, where it is called Xia Jian Dou (挟剑豆, "clasped sword bean"). However, as Li Shizhen noted in the Ben Cao Gang Mu (1596), the herb was absent from the major earlier pharmacopoeias. Li Shizhen provided the first systematic materia medica account, placing it under the Grains section. He recorded both its culinary versatility and its medicinal use for stubborn hiccups, a condition that could be dramatically loud and debilitating after illness.

The Dian Nan Ben Cao (滇南本草, c. 1436) by Lan Mao of Yunnan briefly notes its Spleen-strengthening properties, indicating that practitioners in China's southwestern frontier regions had long valued it as both food and medicine. Over time, its reputation solidified around two core uses: stopping hiccups caused by cold and deficiency in the Stomach, and warming the Kidneys for lumbar pain. The classical method of charring the seeds to ash (shao cun xing, 烧存性) and taking the powder in warm water became a well-known folk remedy for persistent hiccups, recorded across multiple Qing Dynasty texts including the Ben Cao Cong Xin and Lan Tai Gui Fan.

Modern Research

4 published studies investigating the pharmacological effects or clinical outcomes of Dao Dou

1

Ethnobotanical Use, Phytochemistry, Pharmacology, and Toxicity of Canavalia gladiata (Comprehensive Review, 2025)

Qian H, Meng D, Yue L, Xu H, Feng K, Wang J. Drug Design, Development and Therapy. 2025;19:3779-3803.

A comprehensive review systematically analyzing the ethnobotanical use, phytochemistry, pharmacology, and toxicity of Canavalia gladiata. The review identified over 231 chemical components including flavonoids, terpenes, steroids, organic acids, and nitrogenous compounds, and documented pharmacological activities including antioxidant, antitumor, antimicrobial, anti-inflammatory, antiallergic, immunomodulatory, antiobesity, hepatoprotective, and antidiabetic effects. The review noted that immature seeds are poisonous and called for more clinical research trials.

2

Sword Bean (Canavalia gladiata) Pod Anti-Allergic and Anti-Inflammatory Effects (In Vitro and In Vivo Study, 2022)

Ji KY et al. Nutrients. 2022;14(14):2853.

This study investigated the anti-allergic and anti-inflammatory effects of sword bean pod extract. Results showed the extract reduced nitric oxide production, decreased expression of inflammatory mediators iNOS and COX-2, and inhibited NF-kB phosphorylation in cell models. It also modulated Th1/Th2 cell differentiation, suggesting potential therapeutic application for allergic diseases.

PubMed
3

Anti-Inflammatory Effect of Immature Sword Bean Pod in LPS-Induced RAW264.7 Cells (In Vitro Study, 2020)

Hwang KA, Heo W, Hwang HJ, Han BK, Song MC, Kim YJ. Journal of Medicinal Food. 2020;23(11):1183-1191.

This study evaluated the anti-inflammatory potential of immature sword bean pods in lipopolysaccharide-stimulated macrophage cells. The extracts demonstrated significant suppression of inflammatory markers, expanding the known pharmacological profile beyond mature seed preparations.

4

Identification of IL-33 Inhibitory Constituents from Canavalia gladiata Pods (In Vitro Study, 2024)

Antioxidants. 2024;13(7):767.

Researchers isolated 11 compounds from sword bean pod methanol extract and tested their ability to inhibit IL-33/ST2 signaling, a pathway involved in allergic and autoimmune diseases. Three compounds, including two flavonoid glycosides, showed substantial dose-dependent IL-33 inhibitory activity (78-86% inhibition at 100 micromolar), supported by molecular docking simulations.

Research on individual TCM herbs is growing but still limited by Western clinical trial standards. These studies provide emerging evidence and should be considered alongside practitioner expertise.