Herb Fruit (果 guǒ / 果实 guǒ shí)

Xi Gua

Watermelon fruit · 西瓜

Citrullus lanatus (Thunb.) Matsum. et Nakai · Fructus Citrulli

Also known as: Hán Guā (寒瓜, Cold Melon), Xià Guā (夏瓜, Summer Melon), Qīng Mén Lǜ Yù Fáng (青门绿玉房),

Xi Gua (Watermelon fruit) plant

Images shown are for educational purposes only

Watermelon is one of the most popular summer fruits in Chinese medicine, prized for its ability to cool the body, quench thirst, and promote healthy urination during hot weather. Classical physicians called it the 'natural White Tiger Decoction' because its cold, sweet nature rivals that famous formula's power to clear intense heat. It is best suited for people experiencing overheating, excessive thirst, and scanty dark urine, but should be avoided by those with a cold, weak digestive system.

Category Heat-clearing herbs Herbs that clear Summer-Heat (清热解暑药)
Therapeutic focus Summer Heat Relief Urinary Health Summer wellness Oral and Dental Health

TCM Properties

Temperature

Cold

Taste

Sweet (甘 gān)

Channels entered

Heart, Stomach, Urinary Bladder

Parts used

Fruit (果 guǒ / 果实 guǒ shí)

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 Xi Gua does in the body, explained in both everyday and TCM terms

Therapeutic focus

In practical terms, Xi Gua is primarily used to support these areas of health:

Summer Heat Relief Urinary Health Summer wellness Oral and Dental Health

TCM Actions

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

Clears Summer-Heat Generates Fluids and Relieves Thirst Eliminates Irritability Promotes Urination Clears Damp-Heat and Resolves Jaundice

How these actions work

'Clears Summerheat' is the primary and most celebrated action of watermelon. Summerheat is a seasonal pathogenic factor unique to the hot summer months that causes high fever, profuse sweating, intense thirst, and agitation. Watermelon's cold nature and sweet flavour powerfully cool the body and dispel this heat. Classical physicians compared it to the famous Bái Hǔ Tāng (White Tiger Decoction), calling watermelon the 'natural White Tiger Decoction' (天生白虎汤) because it could match that formula's ability to clear intense heat from the Qi level.

'Generates fluids and relieves thirst' refers to watermelon's ability to replenish the body's fluids when they have been damaged by heat. When Summerheat or high fever consumes body fluids, a person becomes extremely thirsty, with a dry mouth and scanty urine. Watermelon's sweet, cold, and abundantly juicy nature directly nourishes these depleted fluids.

'Eliminates restlessness and irritability' means watermelon can calm the agitation that arises when heat disturbs the Heart. Because it enters the Heart channel, it is especially good at clearing the type of heat that causes mental restlessness, irritability, and difficulty sleeping during hot weather.

'Promotes urination' means watermelon helps the body pass more urine, which in TCM is a key way of draining heat and dampness downward and out of the body. This action makes it useful for conditions involving scanty, dark urine, mild edema, or fluid retention.

'Reduces jaundice' refers to watermelon's supportive role in treating icteric hepatitis and other conditions involving yellowing of the skin and eyes. By promoting urination and clearing damp-heat, it helps the body eliminate the pathological dampness and heat that TCM associates with jaundice.

Patterns Addressed

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

Why Xi Gua addresses this pattern

Summerheat is a seasonal pathogenic factor that attacks during the hottest months, causing high fever, profuse sweating, intense thirst, and agitation. Watermelon directly addresses this pattern because its cold thermal nature powerfully clears the Summerheat from the Qi level, while its sweet flavour generates fluids to replace those lost through sweating. Its affinity for the Heart channel allows it to calm the mental restlessness and irritability that Summerheat characteristically produces when it disturbs the Heart. Its action on the Stomach channel helps relieve the intense thirst caused by heat damaging Stomach fluids, and its Bladder channel affinity supports the drainage of heat through increased urination.

A practitioner would look for one or more of these signs

Excessive Thirst

Intense thirst with desire for cold drinks, caused by Summerheat consuming fluids

Fever

High fever from Summerheat invading the Qi level

Irritability

Restlessness and agitation from heat disturbing the Heart

Dark Urine

Scanty, dark yellow urine from heat concentrating body fluids

Commonly Used For

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

Arises from: Summer-Heat

TCM Interpretation

TCM understands heatstroke as a Summerheat invasion. Summerheat is an intense, yang pathogenic factor that attacks during the hottest months. It damages the body on two fronts: it generates intense internal heat (causing high fever, flushed face, and agitation) and it depletes vital fluids through excessive sweating (causing extreme thirst, dry mouth, and scanty urine). The Heart is particularly vulnerable because Summerheat has a natural affinity for the Heart channel, which is why mental confusion and restlessness are hallmark symptoms. In severe cases, the Qi itself collapses from the combined effect of heat and fluid loss.

Why Xi Gua Helps

Watermelon is ideally matched to heatstroke because its cold thermal nature directly counters the intense heat, while its abundant sweet juice replenishes the fluids lost to sweating. Its channel entry into the Heart calms the mental agitation and irritability, while its Stomach channel affinity addresses the burning thirst. Its Bladder channel action promotes urination, providing another route for the body to expel heat downward. This dual action of clearing heat while simultaneously generating fluids is why classical physicians gave watermelon the revered title 'natural White Tiger Decoction' (天生白虎汤), comparing it to the most powerful Qi-level heat-clearing formula in TCM.

Also commonly used for

Edema

Mild fluid retention addressed through its diuretic action

Jaundice

Supportive role in icteric hepatitis by promoting urination and clearing damp-heat

Fever

High fever from Summerheat or Qi-level heat

Dehydration

Fluid loss from heat, sweating, or febrile illness

Urinary Tract Infection

Damp-heat in the lower body with painful, scanty urination

High Blood Pressure

Supportive use, particularly the rind (Xi Gua Cui Yi)

Herb Properties

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

Temperature

Cold

Taste

Sweet (甘 gān)

Channels Entered

Heart Stomach Urinary Bladder

Parts Used

Fruit (果 guǒ / 果实 guǒ shí)

Dosage & Preparation

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

Standard dosage

Fresh fruit: 500–2000g (eaten as food). Dried rind (Xi Gua Cui Yi): 9–30g in decoction. Fresh rind: 60–120g.

Maximum dosage

As a food, there is no strict toxic upper limit, but classical sources warn against overconsumption. For medicinal dried rind decoction, up to 30g is standard; fresh rind up to 120g.

Dosage notes

As a food-medicine, watermelon is primarily consumed fresh in summer for its heat-clearing and fluid-generating benefits. The dried outer rind (Xi Gua Cui Yi) is the form most commonly used in decoctions, at 9–30g, for conditions like summer-heat irritability, scanty urination, oedema, and mouth sores. Fresh watermelon juice can be taken in larger amounts (one bowlful at a time, sipped slowly) for acute heat conditions with high fever and intense thirst. For people with weak Spleen-Stomach function, smaller amounts should be used and the fruit should not be ice-cold. The Ben Cao Hui Yan describes treating Yangming-level Heat with fever and thirst by slowly drinking a bowl of fresh red-fleshed watermelon juice.

Preparation

As a food-medicine, watermelon is typically consumed fresh and raw, or its juice is drunk directly. The dried rind (Xi Gua Cui Yi) is decocted normally with no special handling required. For Watermelon Frost (Xi Gua Shuang), a special preparation is used: the fruit is hollowed out, packed with mirabilite (Mang Xiao), sealed, and hung in a cool ventilated place until white crystals form on the outer rind surface, which are then scraped off and collected.

Processing Methods

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

Processing method

The green outer rind of the watermelon is separated from both the hard outer skin and the red flesh. The rind is washed, cut into strips, and sun-dried for storage and later use in decoctions.

How it changes properties

The rind retains the same sweet, cold properties as the flesh but with reduced sweetness and enhanced diuretic action. It is slightly cooler and more bland (淡) in taste compared to the flesh. Its channel entry remains Heart, Stomach, and Bladder. The rind form is more practical for use in decocted prescriptions and can be stored long-term, unlike the perishable fresh fruit.

When to use this form

When watermelon needs to be incorporated into a formal herbal decoction (the flesh is too watery for decoctions). Xi Gua Cui Yi is the standard form used in classical formulas like Qing Luo Yin and Qing Shu Yi Qi Tang. It is preferred when the diuretic and heat-clearing actions are more important than the fluid-generating action of the fresh juice.

Common Herb Pairs

These ingredients are traditionally combined with Xi Gua for enhanced therapeutic effect

He Ye
He Ye 1:1 (both around 6g when using Xi Gua Cui Yi)

Watermelon (or its rind, Xi Gua Cui Yi) paired with Lotus Leaf (He Ye) creates a powerful Summerheat-clearing duo. Watermelon clears heat and generates fluids from within, while Lotus Leaf's light, ascending nature disperses Summerheat from the exterior and raises clear Yang. Together they address both the internal heat and the head symptoms (dizziness, muzzy-headedness) of Summerheat.

When to use: Summerheat with both thirst and head symptoms such as dizziness, heaviness, and muzzy-headedness, as seen in Qing Luo Yin.

Xi Yang Shen
Xi Yang Shen Xi Gua Cui Yi 30g : Xi Yang Shen 6g (5:1)

Watermelon rind (Xi Gua Cui Yi) combined with American Ginseng (Xi Yang Shen) addresses Summerheat with Qi and Yin depletion. Xi Gua Cui Yi clears the Summerheat directly, while Xi Yang Shen replenishes the Qi and Yin that Summerheat has consumed. This pairing treats both the cause (heat) and consequence (Qi-Yin damage) simultaneously.

When to use: Summerheat with significant fatigue, shortness of breath, and thirst, indicating that both Qi and fluids have been damaged. This is the core pairing of Wang Mengying's Qing Shu Yi Qi Tang.

Jin Yin Hua
Jin Yin Hua 1:1 (both around 6g)

Watermelon rind paired with fresh Honeysuckle Flower combines two light, cool substances for clearing Summerheat from the upper body. Jin Yin Hua adds aromatic, heat-clearing and toxin-resolving power, while Xi Gua Cui Yi contributes cooling and fluid-generating action. Together they clear Summerheat while also addressing any toxic-heat component.

When to use: Mild Summerheat affecting the Lung channel, with low-grade fever, slight thirst, and head discomfort. This pairing appears in Qing Luo Yin from the Wen Bing Tiao Bian.

Key Formulas

These well-known formulas feature Xi Gua in a prominent role

Qing Shu Yi Qi Tang 清暑益氣湯 King

Wang Mengying's Qing Shu Yi Qi Tang (from Wen Re Jing Wei) pairs Xi Gua Cui Yi at a large dose (30g) with Xi Yang Shen as co-King herbs for Summerheat damaging both Qi and fluids. Xi Gua Cui Yi serves as one of the two King herbs, showcasing watermelon rind's premier Summerheat-clearing and fluid-generating action in a clinical formula for more significant heat with exhaustion and dehydration.

Qing Luo Yin 清絡飲 Deputy

Qing Luo Yin from Wu Jutong's Wen Bing Tiao Bian is the classic formula for mild Summerheat affecting the Lung channel. Xi Gua Cui Yi (watermelon rind) serves as a Deputy, contributing its Summerheat-clearing and fluid-generating actions alongside fresh Honeysuckle, Lotus Leaf, and other light, aromatic herbs. This formula perfectly showcases watermelon's role as a gentle, light Summerheat remedy.

Comparable Ingredients

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

Lu Gen
Xi Gua vs Lu Gen

Both Lu Gen (Reed Rhizome) and Xi Gua clear heat and generate fluids, and both are sweet and cold. However, Lu Gen is more commonly used as a decocted medicinal herb in formal prescriptions, has a stronger action on the Lung (clearing Lung heat and resolving phlegm-heat), and can be used year-round. Xi Gua is primarily a seasonal food-medicine best suited for Summerheat specifically, and is used as fresh fruit or juice rather than in decoctions. Xi Gua has a stronger diuretic effect, while Lu Gen is better for treating nausea and vomiting from Stomach heat.

Zhi Mu
Xi Gua vs Zhi Mu

Both Zhi Mu and Xi Gua clear heat from the Qi level and generate fluids. Zhi Mu is bitter, sweet, and cold, entering the Lung, Stomach, and Kidney channels, and is a formal medicinal herb used in decoctions for a wider range of heat patterns including Yin-deficiency heat. Xi Gua is milder, purely sweet, and limited mainly to Summerheat and acute heat with thirst. Zhi Mu is the stronger, more versatile heat-clearing herb for year-round clinical use, while Xi Gua excels as a seasonal dietary remedy for Summerheat.

Dong Gua Pi
Xi Gua vs Dong Gua Pi

Both Xi Gua and Dong Gua Pi (Winter Melon Rind) are sweet, cold melon-derived substances that promote urination and clear heat. However, Dong Gua Pi has a much stronger diuretic and edema-resolving effect and is the preferred choice for significant fluid retention and edema. Xi Gua's primary strength is clearing Summerheat and generating fluids, making it the better choice when thirst and heat are the dominant symptoms. Dong Gua Pi also clears damp-heat more broadly, including in lower-body infections.

Common Substitutes & Adulterants

Related species and common adulterations to be aware of when sourcing Xi Gua

As a common fresh fruit, watermelon itself is rarely adulterated. The main concern is with the dried medicinal rind (Xi Gua Cui Yi, 西瓜翠衣): it may sometimes be confused with winter melon (Dong Gua, 冬瓜) rind, which has different properties. Xi Gua Cui Yi should be clearly greenish on the outer surface with visible network-like vascular bundles, while winter melon rind is thicker and has a waxy bloom. For the prepared product Watermelon Frost (Xi Gua Shuang), counterfeit versions may substitute inferior crystalline powders that lack the authentic preparation method involving mirabilite and natural crystallisation.

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

Toxicity Classification

Classical Chinese pharmacopoeia toxicity rating for Xi Gua

Non-toxic

Watermelon is classified as non-toxic (无毒) across all major classical sources, including the Ri Yong Ben Cao, Yin Shan Zheng Yao, and Ben Cao Gang Mu. There are no toxic components of concern. The primary safety issue is not toxicity but rather overconsumption causing gastrointestinal distress (abdominal distension, diarrhoea, vomiting) due to its cold nature and high water and sugar content. Classical sources warn that excessive intake 'injures the Spleen and promotes Dampness.' The Yuan Dynasty physician Li Pengfei noted that a regional governor who ate too much watermelon in summer developed severe leg and back pain by autumn, illustrating the consequences of cold accumulation from overconsumption.

Contraindications

Situations where Xi Gua should not be used or requires extra caution

Caution

Spleen-Stomach deficiency Cold (脾胃虚寒): Watermelon is cold in nature and can further damage the Spleen and Stomach Yang in people with cold-type digestive weakness, causing diarrhea, abdominal pain, and poor digestion.

Caution

Internal Cold with Dampness accumulation (中寒湿盛): Classical sources explicitly state this as a contraindication. The cold, wet nature of watermelon worsens Cold-Damp patterns.

Caution

Diabetes with poor blood sugar control: Watermelon has a high glycaemic index and significant sugar content. People with diabetes should limit consumption and monitor blood sugar closely.

Caution

Heart failure or severe kidney insufficiency: The high water content of watermelon can lead to fluid overload, worsening oedema and potentially triggering acute heart failure in those with compromised cardiac or renal function.

Caution

Early-stage or Wind-Cold type common cold: Watermelon's cold nature can trap the pathogen and worsen the condition when the exterior has not yet been resolved, especially in Cold-type presentations.

Caution

Chronic diarrhoea or loose stools: The cold, slippery nature of watermelon further weakens Spleen transportation and worsens diarrhoea.

Caution

Postpartum recovery period: Classical sources caution against cold, raw foods during the postpartum period when the body is in a deficient state. Watermelon's cold nature may impair recovery.

Special Populations

Important considerations for pregnancy, breastfeeding, and pediatric use

Pregnancy

Generally considered safe when consumed as a food in moderate amounts during pregnancy. Watermelon can help with hydration and may relieve pregnancy-related heartburn and nausea. However, its cold nature means excessive consumption may cause digestive discomfort, especially in women with a tendency toward Spleen deficiency or loose stools. Its high sugar content should also be considered for those with gestational diabetes. Classical sources list the postpartum period (产后) as a time to avoid watermelon, as the cold nature may impair recovery of Qi and Blood. There is no known mechanism of uterine stimulation or teratogenicity.

Breastfeeding

Generally safe when consumed as a food in moderation during breastfeeding. Watermelon provides hydration and nutrients that can support milk production. However, in TCM theory, excessive consumption of cold-natured foods by the nursing mother may indirectly affect the infant through breast milk, potentially contributing to digestive upset or loose stools in sensitive babies. Mothers with weak digestion or those whose infants have loose stools should limit intake. No specific toxic components are known to transfer through breast milk.

Children

Watermelon is generally suitable for children as a seasonal food. Children under age 3 should be given only small amounts due to their immature digestive systems and the cold nature of the fruit, which can easily cause diarrhoea and stomach upset in young children. For older children, moderate amounts are fine during hot weather. Refrigerated watermelon should be avoided for young children or those with weak digestion. The seeds should be removed for very young children to prevent choking. When using the dried rind medicinally, reduce the adult dose proportionally based on age and body weight.

Drug Interactions

If you are taking pharmaceutical medications, be aware of these potential interactions with Xi Gua

Antihypertensive medications: Watermelon contains L-citrulline, which the body converts to L-arginine and then to nitric oxide, a vasodilator. Consuming large amounts of watermelon alongside blood pressure-lowering drugs (ACE inhibitors, ARBs, calcium channel blockers, diuretics) may produce an additive blood pressure-lowering effect, potentially causing hypotension, dizziness, or lightheadedness.

Nitrate medications: Drugs that increase blood flow to the heart, such as nitroglycerin and isosorbide, should be used with caution alongside large watermelon consumption. The combined vasodilatory effects could cause a dangerous drop in blood pressure.

Potassium-sparing diuretics: Watermelon is rich in potassium. Combined with potassium-sparing diuretics (spironolactone, amiloride), excessive consumption could contribute to hyperkalaemia. Potassium levels should be monitored.

Note: These interactions are primarily relevant when watermelon or L-citrulline is consumed in concentrated or supplemental quantities, rather than ordinary dietary intake.

Dietary Advice

Foods and dietary considerations when taking Xi Gua

While consuming watermelon medicinally, avoid eating it together with oily or greasy foods, as classical sources note this combination can further damage the Spleen. Avoid ice-cold or heavily refrigerated watermelon, as this intensifies the cold nature and is more likely to cause digestive upset. Pair with warming foods like ginger tea if mild stomach discomfort occurs after eating watermelon. People with cold constitutions or during cooler seasons should consume watermelon sparingly and at room temperature.

Botanical Description

Physical characteristics and morphology of the Xi Gua source plant

Citrullus lanatus (Thunb.) Matsum. et Nakai is an annual trailing vine in the Cucurbitaceae (gourd) family. The stems are slender, creeping along the ground, with distinct ridged grooves and forked tendrils. The leaves are alternate, triangular-ovate to broadly ovate, 8–20 cm long and 5–18 cm wide, deeply three-lobed with further irregular pinnate divisions, and covered in fine hairs on both surfaces.

The plant is monoecious, bearing separate male and female yellow flowers in leaf axils. Male flowers are about 2–2.5 cm in diameter with a funnel-shaped corolla. Female flowers are somewhat larger. The fruit is a large pepo (gourd-type fruit), round to oblong, typically 20–40 cm in diameter, with a smooth green rind often marked with darker green stripes. The flesh (pulp) is juicy and typically red, pink, or sometimes yellow, containing numerous flat, oval seeds that can be black, red, white, or yellow.

Watermelon thrives in warm, dry climates with ample sunlight, preferring temperatures of 20–35°C and well-drained sandy loam soils. It is drought-tolerant but not cold-hardy. Flowering and fruiting occur in summer.

Sourcing & Harvesting

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

Harvesting season

Summer (typically June to August), when the fruit is fully ripe.

Primary growing regions

Watermelon is cultivated across virtually all provinces of China. Unlike most medicinal herbs, it does not have a single recognized 'terroir' (道地药材) region, as it is primarily a food crop. However, regions known for producing particularly high-quality, sweet watermelons include Xinjiang (especially Hami, Turfan, and the Junggar Basin areas), Ningxia (especially Zhongwei, famous for its 'selenium-sand watermelons'), Shandong, Henan, Hebei, and Anhui. In southern China, smaller-fruited varieties predominate, while northern regions grow larger varieties. Guangxi and Hainan are important for off-season production. Globally, watermelon originated in sub-Saharan Africa and is now widely grown in tropical and temperate regions worldwide, with China being by far the world's largest producer.

Quality indicators

Good quality medicinal watermelon fruit should be large, with a deep red flesh (红瓤) and a sweet taste. The flesh should be firm but juicy, not mushy or mealy. A ripe watermelon sounds hollow and deep when tapped (a crisp sound indicates under-ripeness). The rind should be firm and uniformly coloured. For the dried rind (Xi Gua Pi / Xi Gua Cui Yi used medicinally), good quality pieces are thin, greenish on the outer surface, yellowish-white inside with visible vascular bundle patterns, brittle in texture, odourless, and bland in taste. Avoid darkened, mouldy, or overly thick rind pieces.

Classical Texts

Key passages from the classical Chinese medical texts that describe Xi Gua and its therapeutic uses

《日用本草》(Rì Yòng Běn Cǎo, Daily Use Materia Medica)

Original: 消暑热，解烦渴，宽中下气，利小水，治血痢。

Translation: Clears summer-heat, relieves restless thirst, relaxes the middle and descends Qi, promotes urination, and treats bloody dysentery.

《饮膳正要》(Yǐn Shàn Zhèng Yào, Principles of Correct Diet)

Original: 主消渴，治心烦，解酒毒。

Translation: Principally treats wasting-thirst, addresses heart-vexation, and resolves alcohol toxicity.

《本经逢原》(Běn Jīng Féng Yuán)

Original: 西瓜，能引心包之热，从小肠、膀胱下泄。能解太阳、阳明中暍及热病大渴，故有天生白虎汤之称。

Translation: Watermelon can draw Heat from the Pericardium and discharge it downward through the Small Intestine and Bladder. It resolves heat-stroke of the Taiyang and Yangming channels and the great thirst of febrile diseases, hence its reputation as the 'Natural White Tiger Decoction.'

《丹溪心法》(Dān Xī Xīn Fǎ, Danxi's Experiential Therapy)

Original: 治口疮甚者，用西瓜浆水徐徐饮之。

Translation: For severe mouth sores, slowly drink watermelon juice as treatment.

《本草纲目》(Běn Cǎo Gāng Mù, Compendium of Materia Medica)

Original: 西瓜、甜瓜，皆属生冷，世俗以为醍醐灌顶，甘露洒心，取其一时之快，不知其伤脾助湿之害也。

Translation: Watermelon and muskmelon are both cold and raw in nature. People treat them as if they were the finest balm poured over the crown or sweet dew sprinkled on the heart, enjoying momentary pleasure, unaware of the harm of injuring the Spleen and promoting Dampness.

Historical Context

The history and evolution of Xi Gua's use in Chinese medicine over the centuries

The name Xi Gua (西瓜, literally 'Western Melon') reflects the traditional belief that the fruit was introduced to China from the western regions. According to the Ben Cao Gang Mu, the Song-era scholar Hu Qiao obtained watermelon seeds while among the Khitan people, who had in turn acquired them from the Uyghurs (回纥). This account places the introduction of watermelon into central China around the Five Dynasties period (10th century CE). However, the botanist Tao Hongjing (陶弘景) of the Liang Dynasty noted a 'cold melon' (寒瓜) from the Yongjia region centuries earlier, which Li Shizhen believed was an earlier, unnamed form of watermelon already present in eastern Zhejiang before it became widespread.

Archaeological evidence complicates this narrative further: watermelon seeds have been found in Han Dynasty tombs in Guangxi and Jiangsu, and reportedly even at a Neolithic site in Zhejiang, potentially pushing the history of watermelon in China back thousands of years. The famous nickname 'Natural White Tiger Decoction' (天生白虎汤), attributed to Wang Ying's Shi Wu Ben Cao (《食物本草》), compares its heat-clearing and fluid-generating power to the classical formula Bai Hu Tang from the Shang Han Lun. This vivid comparison cemented watermelon's identity as the quintessential summer-heat remedy in Chinese medicine.

A related medicinal product, Watermelon Frost (西瓜霜, Xi Gua Shuang), is made by packing the hollowed rind with mirabilite (Glauber's salt) and collecting the white crystals that form on the outer surface. This preparation became one of the most celebrated throat remedies in Chinese medicine, often called a 'sacred medicine for throat disorders' (喉科圣药).

Modern Research

4 published studies investigating the pharmacological effects or clinical outcomes of Xi Gua

1

Watermelon and L-Citrulline in Cardio-Metabolic Health: Review of the Evidence 2000-2020 (Narrative Review, 2022)

Hong MY, Beidler J, Hooshmand S, Figueroa A, Kern M. Current Atherosclerosis Reports, 2022, 24(4), 223-234.

This review examined preclinical and clinical trial evidence on watermelon and its signature compound L-citrulline for cardiovascular and metabolic health. The authors found that watermelon and L-citrulline supplementation reduced blood pressure in human trials and identified emerging benefits for glucose homeostasis, gut health, and brain health through nitric oxide bioavailability in tissues.

PubMed
2

Effects of L-citrulline supplementation and watermelon consumption on vascular function and cardiometabolic risk markers: A meta-analysis of RCTs in adults (Meta-analysis, 2022)

Smeets ETHC, Mensink RP, Joris PJ. British Journal of Nutrition, 2022, 128(7), 1393-1406.

This meta-analysis of 17 randomised controlled trials found that longer-term L-citrulline supplementation significantly improved vascular endothelial function (flow-mediated dilation increased by 0.9 percentage points), while longer-term watermelon consumption improved arterial stiffness (pulse wave velocity decreased by 0.9 m/s). Postprandial glucose also decreased by 0.6 mmol/L after watermelon consumption.

PubMed
3

L-citrulline supplementation and watermelon intake reduce blood pressure in middle-aged and older adults: A systematic review and meta-analysis of RCTs (Meta-analysis, 2025)

Li P, Chen JF, Li K, Zhao J. Complementary Therapies in Medicine, 2025.

A meta-analysis of 15 RCTs involving 415 middle-aged and elderly participants found that L-citrulline supplementation and watermelon intake significantly reduced systolic blood pressure by 4.02 mmHg and diastolic blood pressure by 2.54 mmHg. Combined supplementation of L-citrulline and L-arginine showed even more pronounced effects.

PubMed
4

Potential roles of Citrulline and watermelon extract on metabolic and inflammatory variables in diabetes mellitus (Systematic Review, 2020)

Aguayo E, Martínez-Sánchez A, Fernández-Lobato B, Alacid F. Diabetology & Metabolic Syndrome, 2020, 12, 40.

This systematic review of 8 studies found that citrulline and watermelon extract supplementation increased nitric oxide synthesis, significantly reduced blood glucose in four studies, and decreased inflammatory biomarkers in two studies. The authors concluded these interventions could improve glycaemic status and inflammation in diabetes, though further mechanistic research is needed.

PubMed

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.