Chinese Knotweed and Pig Blood Soup: A Complete Guide

Educational Overview of Polygonum chinense (Chinese Knotweed) and Pig’s Blood Medicinal Soup

Introduction to Medicinal Diet

The Fire Charcoal Mother and Pork Blood Soup (Huotan Mu Zhuhong Tang) is a time-honored traditional medicinal diet in the Lingnan region, particularly widespread in Guangdong and Guangxi. This soup is crafted with the core ingredients of the herb *Polygonum chinense* L. (Fire Charcoal Mother, also known as Chinese knotweed) and fresh pork blood (pork red), complemented by ginger, red dates, and other adjuncts that are meticulously simmered. *Polygonum chinense* L., also called *Chidi Li* or *Wu Tan Zi*, is the dried whole herb of the Polygonaceae family, renowned in folk herbalism as the “heat-clearing and detoxifying herb.” Pork blood, rich in iron and various amino acids, is considered a “blood-nourishing delicacy” on the common table. Combining these two into a soup not only yields a delicious flavor and clear broth but also embodies the centuries-old wisdom of “medicine and food homology.” It is a seasonal soup ideal for clearing summer heat and removing dampness in summer, as well as moistening dryness and cleansing the intestines in autumn and winter.

Regarding the origin of *Polygonum chinense* (Chinese knotweed) and Pig Blood Soup (Huotanmu Zhu Hong Tang), a folk tale has circulated through the ages. It is said that in ancient times, the Lingnan region was plagued by oppressive summerheat-dampness, making villagers prone to dysentery and toxic sores. An elderly herb gatherer once noticed that pigs feeding in thickets of *Polygonum chinense* exhibited glossy coats and robust health. He then boiled the herb with pig blood left from the annual New Year slaughter and distributed the soup to the afflicted villagers. Unexpectedly, it produced remarkable curative effects. From then on, this soup was passed down through generations among the hamlets, gradually moving from the fields and farmsteads into urban streets and alleys, eventually becoming a uniquely flavored health-nourishing soup in tea houses and restaurants. Today, *Polygonum chinense* and Pig Blood Soup is not only an effective formula for dispelling disease but also a daily choice for ordinary families to regulate their diet and nourish the body.

Soup Features

From a visual perspective, the soup presents a light brown or pale red hue, with pig’s blood curd cubes as tender and smooth as tofu. The leaves of Chinese knotweed (*Polygonum chinense*) spread out gracefully, and the stem segments are clearly defined, accented by golden slices of ginger and glossy red dates—elegant yet warming. On the palate, the first taste reveals the fresh, tender, and springy texture of pig’s blood, quickly followed by the distinctive slight astringency and sweet aftertaste of Chinese knotweed, which eventually harmonizes into a full, gentle warmth under the influence of ginger and jujube. It lacks the strong medicinal smell typical of many therapeutic dishes, instead blending the four flavors of lightness, freshness, sweetness, and moistness, allowing diners to reap health benefits almost imperceptibly.

Efficacy of Medicinal Diet

The core effects of Polygonum chinense and Pig’s Blood Soup can be summarized by four key actions: “Clear, Drain, Tonify, and Moisten.” “Clear” refers to clearing heat and resolving toxin, effectively eliminating internal heat toxin and alleviating discomfort such as sore throat, oral ulcers, and red, swollen eyes due to summerheat and damp toxin. “Drain” indicates draining dampness and stopping diarrhea; it significantly improves conditions like loose stools, dysentery, and thick yellow vaginal discharge caused by damp-heat pouring downward, helping restore normal transportation and transformation function of the intestines. “Tonify” means tonifying blood and nourishing deficiency; pig’s blood is rich in heme iron, which is easily absorbed by the body, and provides good tonifying effects for iron-deficiency anemia, sallow complexion, dizziness, and fatigue. “Moisten” refers to moistening dryness and lubricating the intestines; the water and gelatinous components in the soup moisten the intestines and relieve dry stool, while the cool nature of Polygonum chinense counteracts the potential greasiness of pig’s blood, promoting bowel movement without damaging the righteous qi.

Modern nutritional and pharmacological studies have also provided supporting evidence for the efficacy of this medicinal diet. *Polygonum chinense* (Chinese knotweed) contains various active components such as flavonoids, phenolic acids, and triterpenoids, exhibiting broad-spectrum antibacterial, antiviral, anti-inflammatory, and antioxidant effects. In particular, it shows strong inhibitory activity against intestinal pathogenic bacteria such as *Shigella* and *Escherichia coli*. Pig blood is rich in protein, iron, zinc, selenium, and multiple vitamins. When the plasma proteins in pig blood are decomposed by gastric acid in the human body, they produce a substance with detoxifying effects, which helps eliminate harmful materials such as dust and metal particles from the intestinal tract. Therefore, this soup indeed possesses a modern scientific basis for “clearing intestinal toxins and nourishing qi and blood.”

The Roles of Traditional Chinese Medicine

From the perspective of Traditional Chinese Medicine’s theory of flavor, nature, and meridian entry, *Huo Tan Mu* (火炭母, *Polygonum chinense*, Chinese knotweed) is sour and sweet in flavor, cool in nature, and enters the Liver (LV) and Spleen (SP) meridians. The sour flavor astringes, stopping diarrhea and securing the intestines; the sweet flavor tonifies, harmonizing the middle and relieving urgency; the cool nature clears heat, draining fire and resolving toxicity. It is especially skilled at clearing damp-heat from the Liver and Spleen meridians, making it a symptomatic choice for conditions such as abdominal pain, diarrhea, and dysentery caused by Liver overacting on Spleen (*mu ke tu*) with damp-heat stagnation. *Zhu Hong* (猪红, pig’s blood, *Sus scrofa domesticus* blood) is salty in flavor, neutral in nature, and enters the Liver (LV) meridian. The salty flavor softens hardness and dissipates masses, assisting in dispersing internal stasis; the neutral nature makes its action gentle, neither cold nor hot, suitable for long-term regulation. *Zhu Hong* directly enters the Liver meridian, nourishing blood with blood, and provides direct supplementation for Liver blood deficiency presenting as dizziness, blurred vision, palpitations, and insomnia.

The combination of the two ingredients enhances each other’s effects. *Polygonum chinense* (Huotannu) primarily clears heat, drains dampness, cools the blood, and detoxifies, while pig’s blood (Zhuhong) mainly nourishes blood, supports the liver, moistens the intestines, and unblocks bowels. One clears and one supplements; one drains and one nourishes—this ensures the formula clears without harming the *zhengqi* (righteous qi) and supplements without retaining pathogenic factors. This combination is especially suitable for the “mixed deficiency and excess” pattern that blends *damp-heat* constitution and *blood deficiency* constitution. During the decoction process, the addition of ginger and jujube embodies the harmonizing wisdom of Chinese medicine: *Shengjiang* (fresh ginger, *Zingiber officinale*), pungent and warm, disperses water qi, removes the slight fishy taste of pig’s blood, and prevents the overly cool nature of *Polygonum chinense* from impairing the stomach. *Hongzao* (red jujube, *Ziziphus jujuba*), sweet and warm, supplements the middle and boosts qi, nourishes blood and calms the spirit, thereby enhancing the formula’s tonifying effects. The combined ingredients achieve the subtle effect of “clearing heat and draining dampness without damaging the spleen, while supplementing blood and moistening the intestines without promoting dampness.”

Classical Herb Pairing Analysis

From the perspective of TCM formulary, the combination of *Polygonum chinense* (Chinese knotweed) and pig’s blood (*Sus scrofa domestica*) resembles the relationship between the sovereign (jun) and minister (chen) herbs in the “jun-chen-zuo-shi” (sovereign-minister-assistant-envoy) structure. *Polygonum chinense* acts as the sovereign, used in a larger dosage, as the main agent for clearing heat, draining dampness, resolving toxicity, and stopping diarrhea. Pig’s blood acts as the minister, assisting the sovereign by tonifying blood and moistening the intestines, while its rich nutritional content mitigates the bitter-cold nature of *Polygonum chinense* that could harm the stomach. Fresh ginger (*Zingiber officinale*) and Chinese red dates (*Ziziphus jujuba*) together serve as the envoy, harmonizing the various ingredients and protecting the spleen and stomach. The entire formula is rigorously structured, not only embodying the principle of “treat the acute condition by addressing the manifestation” (clearing heat, draining dampness, and stopping diarrhea) but also considering “treat the chronic condition by addressing the root” (tonifying blood, nourishing the liver, and strengthening the spleen). It excellently demonstrates the unique charm of medicinal cuisine, where “treatment is embedded in food.”

Indications

Fire Coal Mother and Pig Blood Soup (火炭母猪红汤) is particularly suitable for the following populations: 1. Those prone to diarrhea, dysentery, or loose stools during the summer-damp season, especially individuals experiencing intestinal discomfort at the turn of summer and autumn due to indulgence in cold drinks or unclean food. This soup can quickly clear intestinal heat and stop diarrhea. 2. Patients with iron-deficiency anemia presenting with sallow complexion, pale lips and nails, and frequent dizziness and fatigue. The high iron content of pig blood combined with the blood-cooling action of Fire Coal Mother (Herba Polygoni Chinensis) can enrich the blood without generating heat. 3. Individuals with “excessive internal heat” patterns due to prolonged sleep deprivation, preference for spicy foods, and susceptibility to acne or oral ulcers. This soup can clear and resolve blood-level heat toxins, improving skin conditions. 4. Workers exposed to dust or long-term smokers. The plasma protein in pig blood helps clear harmful particles from the respiratory tract and intestines, functioning as a “bodily scavenger.”

Furthermore, menopausal women experiencing hot flashes, night sweats, irritability, and insomnia may also benefit from moderate consumption of this soup to obtain a cooling and mind-calming effect. For children with restless sleep at night, foul-smelling or sticky stools caused by food accumulation transforming into heat, small doses administered under accurate pattern differentiation can achieve the effect of reducing accumulation and clearing heat. In summary, this soup is particularly suitable as a daily dietary regulation for individuals with the ‘Damp-Heat Accumulation’ pattern (湿热蕴结) and the ‘Blood Deficiency with Heat’ pattern (血虚有热).

Contraindicated populations

Although Fireweed Herb and Pig’s Blood Soup (Huǒ Tàn Mǔ Zhū Hóng Tāng) has a wide range of effects, it is not suitable for everyone. Those with Spleen-Stomach Yang Deficiency with Cold should use it with caution or avoid it altogether. *Polygonum chinense* (Chinese knotweed) is cool in nature, while pig’s blood is slightly cool and neutral. If one normally experiences aversion to cold, cold pain in the epigastrium and abdomen, loose stools or undigested food in stool, and a pale, enlarged tongue with a white slippery coating, consuming this soup may worsen deficiency-cold symptoms, leading to diarrhea or stomach pain. Pregnant women must use it under the guidance of a physician. The blood-cooling and dampness-draining action of *Polygonum chinense* may disturb the fetal origin (fetal qi), especially during early pregnancy (first trimester) and in women with a history of recurrent miscarriage; such individuals should avoid consuming it. Although pig’s blood is rich in iron, if its source is unclear or if it is improperly processed, it may contain harmful substances. Pregnant women should be especially cautious and choose fresh, hygienic pig’s blood.

Additionally, patients with hypercholesterolemia or during acute gout attacks should limit their intake appropriately. Pig blood contains cholesterol and purines; although not as high as in animal organ meats, excessive consumption may still affect blood lipid and uric acid levels. Patients taking anticoagulant medications (e.g., warfarin) should also avoid long-term or large intake, as *Polygonum chinense* (Chinese knotweed) has certain anticoagulant activity, which may synergize with the drug and increase bleeding risk. Infants (especially those under 1 year old) have immature digestive function and should not consume these foods. Finally, the rare individuals who are allergic to *Polygonum chinense* (Chinese knotweed) or pig blood should naturally avoid them.

Ingredient proportions in the formula

Prepare a standard Fire Charcoal Mother and Pig Blood Soup (serves 3-4 people) using the following precise ratios: 150 g fresh Polygonum chinense (Chinese knotweed) (or 50 g if dried), 300 g fresh pig blood, 15 g fresh ginger (about 5 slices), 6 red dates (about 30 g), salt to taste (about 3-5 g, added last for seasoning), and 2000 ml water (about 8 bowls). This ratio balances medicinal effect and taste, with a moderate amount of Polygonum chinense ensuring a notable action of clearing heat and draining dampness without an overly strong herbal flavor. The proportion of pig blood to Polygonum chinense is approximately 2:1, making the soup tender, delicious, and effective for nourishing blood.

In practice, fine adjustments can be made according to the season and individual constitution. When summer heat is pronounced, increase Huotanmu (Polygonum chinense, Chinese knotweed) to 180 g (fresh) and add 10 g of Mung Bean (Vigna radiata) to enhance heat-clearing. If blood deficiency is evident with a pale complexion, increase pig blood to 350 g and additionally add a small amount of Dang Gui (Angelica sinensis, Dong Quai) (approximately 5 g) to supplement and invigorate blood. For those with a slightly weak spleen and stomach who may be susceptible to cold natured ingredients damaging the stomach, increase Sheng Jiang (Zingiber officinale, fresh ginger) to 20 g and include a small piece of Chen Pi (Citrus reticulata, tangerine peel) (about 3 g) to regulate qi and harmonize the stomach. It is recommended to use Hong Zao (Ziziphus jujuba, red dates) with the pits removed, as the pits are somewhat drying in nature; removing them makes the soup more neutral. Salt should be added last, just before serving, as adding it too early will harden the pig blood and affect the texture.

Preparation Method

Step 1: Prepare the ingredients. Remove the old stems and withered leaves from fresh *Persicaria chinensis* (Chinese knotweed), rinse thoroughly under running water, drain, and cut into sections about 5 cm long (if using dried herb, soak in cold water for 30 minutes in advance, then rinse and cut). Gently rinse the pig blood curd (pig blood tofu) with clean water, cut into cubes approximately 2 cm square, and set aside in a bowl. Wash and slice fresh ginger (Zingiber officinale), and rinse the red dates (Ziziphus jujuba) to remove pits.

Step 2: Blanch the pig blood. Add an appropriate amount of water to a pot (enough to fully submerge the pig blood). Bring to a boil over high heat, then carefully add the pig blood cubes. At the same time, add 1 teaspoon of cooking wine (about 5 ml) and 2 slices of fresh ginger. Blanch over medium heat for about 2 minutes. Once the pig blood changes color and floats to the surface, immediately remove and drain well. This step removes the fishy smell and excess moisture from the pig blood, resulting in a clear and non-cloudy soup.

Step three: Decoction preparation. Take a clay pot or ceramic soup pot, add 2000 ml of water (approximately 8 bowls), and put in the processed Chinese knotweed (Polygonum chinense), the remaining ginger slices, and red dates (Ziziphus jujuba). Cover with a lid, bring to a boil over high heat, then reduce to low heat and simmer gently for 45 minutes, until the decoction turns light brown in color and rich in medicinal aroma. Maintain a slight simmer throughout, avoiding boiling the water dry with high heat.

Step 4: Combine and simmer into a soup. Gently place the blanched pig blood pieces into the simmered medicinal decoction, turn to medium heat and cook for 5–8 minutes, allowing the blood to fully absorb the flavor of the decoction. During this process, use a spoon to gently stir the blood pieces to ensure even heating, but avoid vigorous stirring to prevent them from breaking apart. Finally, season with salt, stir evenly, and turn off the heat. Before serving, you may sprinkle a small amount of chopped green onion or coriander leaves to enhance color and aroma (optional).

Step 5: Serve the soup. Ladle the cooked Polygonum chinense (Chinese knotweed) pig blood soup into bowls and consume while warm. The pig blood is tender and smooth, the broth clear and refreshing, with the aroma of medicinal herbs blending with the meat, stimulating the appetite. It is recommended to finish the soup within one meal and not to store it for long, as the pig blood may re-harden and the medicinal efficacy may be lost.

Drinking Tips

1. Optimal consumption timing: It is recommended to take one bowl (approximately 250–300 ml) warm on an empty stomach 1 hour before lunch or dinner, 2–3 times per week, with a continuous 2-week regimen as one treatment cycle. Taking the decoction on an empty stomach enhances absorption of the medicinal effects and prevents interference from post-meal fullness. If used as an adjunctive treatment for acute diarrhea or dysentery, it may be taken twice daily (once in the morning and once in the evening), but the dosage should be reduced or discontinued as soon as symptoms subside, to avoid overcorrection.

2. Taste optimization suggestions: If the slight astringency of Polygonum chinense (Chinese knotweed) is too strong, add a small piece of rock sugar (about 5 g) or half a Siraitia grosvenorii (monk fruit, crushed) while simmering the medicinal decoction. This will neutralize the astringency without affecting the efficacy. When blanching the pig’s blood, add a little cooking wine and ginger to the water to effectively remove any unpleasant odor. For children or family members unaccustomed to the taste of medicinal cuisine, extend the cooking time of the red dates (jujube) slightly to allow their fragrance to fully infuse the soup, enhancing its sweetness and smoothness.

3. Safety Precautions: Pig blood must be sourced from a reputable vendor as a fresh product on the same day, avoiding any that has been stored for too long or has an abnormal odor. If Polygonum chinense (Chinese knotweed) is collected from the wild, the collection site should be confirmed to be away from sources of contamination (such as farmlands or roads), and careful identification is necessary to prevent accidental harvest of toxic plants. Avoid using iron or aluminum cookware during decoction, as the tannins in Polygonum chinense may combine with metal ions, potentially affecting the medicinal efficacy and generating harmful substances; earthenware, ceramic, or glass pots are preferred. Lastly, this soup is a medicated dietary formula for health regulation and cannot substitute medical treatment. If symptoms are severe or persist without relief, consult a physician promptly.