Herb Whole plant / Aerial parts (全草 quán cǎo)

Hai Zao

Sargassum seaweed · 海藻

Sargassum pallidum (Turn.) C.Ag. / Sargassum fusiforme (Harv.) Setch. · Sargassum

Also known as: Seaweed

Hai Zao (Sargassum seaweed) plant

Images shown are for educational purposes only

Hai Zao is a type of seaweed used in Chinese medicine primarily to soften and dissolve lumps, nodules, and swellings. It is best known for addressing thyroid enlargement (goiter), swollen lymph nodes, and testicular swelling. It also helps the body expel excess fluids, making it useful for certain types of edema.

Category Phlegm-transforming herbs (化痰药) Herbs that cool and transform Phlegm-Heat (清化热痰药)
Therapeutic focus Thyroid Health Lymphatic Health Nodule and Mass Support Fluid Retention and Edema

TCM Properties

Temperature

Cold

Taste

Bitter (苦 kǔ), Salty (咸 xián)

Channels entered

Liver, Stomach, Kidneys

Parts used

Whole plant / Aerial parts (全草 quán cǎo)

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What This Herb Does

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

Therapeutic focus

In practical terms, Hai Zao is primarily used to support these areas of health:

Thyroid Health Lymphatic Health Nodule and Mass Support Fluid Retention and Edema

TCM Actions

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

Dissipates Nodules and Softens Hardness Dissolves Phlegm Promotes Urination and Reduces Edema

How these actions work

'Softens hardness and dissipates nodules' (软坚散结 ruǎn jiān sàn jié) means Hai Zao can help break down hard lumps, masses, and swellings in the body. Its salty taste has a natural softening effect on hardened tissue, while its cold nature helps clear the Heat that often accompanies chronic nodules. This is why it has been a go-to herb for centuries for conditions like goiter (thyroid enlargement), swollen lymph nodes (scrofula), and testicular swelling. It enters the Liver and Kidney channels, which govern the areas where these conditions commonly develop.

'Dissolves Phlegm' (消痰 xiāo tán) refers to Hai Zao's ability to resolve pathological Phlegm, which in TCM does not just mean mucus in the throat. Phlegm can congeal under the skin or in the organs to form lumps, cysts, and masses. Hai Zao's bitter taste helps dry and disperse this congealed Phlegm, while its salty quality breaks it down. This action works hand-in-hand with its nodule-dissolving effect.

'Promotes urination and reduces edema' (利水消肿 lì shuǐ xiāo zhǒng) means Hai Zao helps the body move and expel excess water. Though this is considered a secondary action (and Hai Zao is usually combined with stronger diuretic herbs like Fu Ling or Ze Xie for this purpose), it contributes to the overall strategy of clearing fluid stagnation from the body.

Patterns Addressed

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

Why Hai Zao addresses this pattern

Hai Zao's cold nature directly clears the Heat component of Phlegm-Fire, while its bitter taste dries Phlegm and its salty taste softens the hardened masses that Phlegm-Fire produces when it congeals. By entering the Liver and Stomach channels, Hai Zao targets the areas where Phlegm-Fire most commonly manifests as visible nodules: the neck (goiter, scrofula) and the lower abdomen (testicular swelling). This makes it a primary herb for dissolving the hard, stubborn accumulations that are the hallmark of this pattern.

A practitioner would look for one or more of these signs

Goiter

Goiter or thyroid enlargement from Phlegm-Fire congealing in the neck

Reactive Lymphadenopathy

Swollen, hard lymph nodes (scrofula)

Testicular Pain

Testicular swelling and pain from Phlegm and Qi accumulation

Commonly Used For

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

Arises from: Phlegm Phlegm

TCM Interpretation

TCM views thyroid nodules as a result of Phlegm and stagnant Qi accumulating in the neck. The Liver's role in ensuring the smooth flow of Qi is central: emotional stress, frustration, or suppressed anger can cause Liver Qi stagnation, which over time impairs the body's ability to transform and transport fluids. These fluids congeal into Phlegm, which settles in the neck area along the Liver and Stomach channels. When this Phlegm hardens, it forms the palpable nodules we recognize as thyroid nodules. If the stagnation generates Heat, the condition falls under the Phlegm-Fire pattern.

Why Hai Zao Helps

Hai Zao directly targets the pathomechanism of thyroid nodules. Its salty taste softens the hardened Phlegm masses, while its bitter, cold nature clears any accompanying Heat and resolves the underlying Phlegm accumulation. It enters the Liver and Stomach channels, which are precisely the channels that pass through the neck where thyroid nodules develop. Hai Zao also contains natural iodine, which from a biomedical perspective directly supports healthy thyroid function. This is why Hai Zao serves as the principal herb in Hai Zao Yu Hu Tang, the most widely used classical formula for thyroid conditions.

Also commonly used for

Hyperthyroidism

Used in larger doses short-term alongside Kun Bu to manage thyroid overactivity

Hypothyroidism

Regular doses used long-term to address iodine-deficiency hypothyroidism

Reactive Lymphadenopathy

Chronic or tuberculous lymph node enlargement (scrofula)

Testicular Pain

Testicular swelling, orchitis, and epididymitis

Edema

As an adjunctive herb for water retention and swelling

Hyperlipidemia

Modern clinical applications include addressing elevated blood lipids

Chronic Bronchitis

For Phlegm accumulation in the lungs with chronic cough

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

Bitter (苦 kǔ), Salty (咸 xián)

Channels Entered

Liver Stomach Kidneys

Parts Used

Whole plant / Aerial parts (全草 quán cǎo)

Dosage & Preparation

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

Standard dosage

6-12g

Maximum dosage

Up to 15g in some clinical applications for goiter or stubborn nodules, under practitioner supervision

Dosage notes

The standard decoction dose is 6-12g. For treating goiter (瘿瘤) and thyroid nodules, the full dose of 10-12g is commonly used. For milder conditions such as edema or phlegm accumulation, lower doses of 6-9g may suffice. Hai Zao can also be taken as wine-soaked preparation (酒渍), ground into powder, or formed into pills. When using Hai Zao for its iodine content in thyroid disorders, practitioners should be aware that it may temporarily suppress hyperthyroid symptoms but cannot treat the underlying condition long-term. In patients with hyperthyroidism, iodine-rich herbs like Hai Zao should generally be avoided.

Preparation

Hai Zao should be rinsed with fresh water before use to reduce excess salt. It is typically cut into segments after being briefly softened, then dried before storage or decoction. No special decoction handling (such as decocting first or adding late) is required. It can also be soaked in wine for treating scrofula and goiter, as described in classical formulas from the Zhou Hou Fang.

Processing Methods

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

Processing method

The raw seaweed is soaked briefly in fresh water to remove excess salt, then drained, cut into segments, and sun-dried.

How it changes properties

This standard preparation removes the harsh saltiness and any sand or impurities from the marine environment. The core properties (bitter, salty, cold) and actions remain largely unchanged, but the reduced salt content makes it gentler on the Stomach and easier to combine with other herbs in decoction.

When to use this form

This is the standard form used in virtually all clinical applications. Raw, unwashed Hai Zao is rarely used directly due to its heavy salt content and marine impurities.

Common Herb Pairs

These ingredients are traditionally combined with Hai Zao for enhanced therapeutic effect

Kun Bu
Kun Bu 1:1 (equal amounts, commonly 10-15g each)

Hai Zao and Kun Bu are the most classic seaweed pair in Chinese medicine. Both are salty and cold with Phlegm-dissolving and hardness-softening actions, and together they produce a significantly stronger effect than either alone. Hai Zao is considered stronger at softening hardness and dispersing clumps (especially in the Liver channel), while Kun Bu excels at softening hardness and promoting water metabolism. Together, they synergistically address all forms of Phlegm nodules.

When to use: Whenever there are hard nodules, masses, or swellings that need to be softened and dissolved, particularly goiter, thyroid nodules, lymph node enlargement, and testicular swelling.

Xia Ku Cao
Xia Ku Cao 1:2 (Hai Zao 10g : Xia Ku Cao 15-20g)

Hai Zao softens hardness and dissolves Phlegm nodules through its salty, cold nature, while Xia Ku Cao (Prunella) clears Liver Fire and disperses stagnation through its bitter, acrid nature. Together they address both the Phlegm accumulation and the Liver Fire that often drives nodule formation, making them particularly effective for nodules with Heat signs.

When to use: Scrofula (lymph node tuberculosis), thyroid nodules, or breast lumps accompanied by signs of Liver Fire such as irritability, red eyes, or a bitter taste in the mouth.

Zh
Zhe Bei Mu 1:1 (equal amounts, commonly 10g each)

Hai Zao softens and dissolves hardened Phlegm masses from the outside, while Zhe Bei Mu (Zhejiang Fritillaria) clears Heat and transforms Phlegm from within. Together, they tackle Phlegm nodules through complementary mechanisms: Hai Zao working on the hard structure of the nodule itself, and Zhe Bei Mu resolving the underlying Phlegm-Heat that generates and sustains it.

When to use: Goiter, scrofula, or other Phlegm nodules, especially when there are signs of Phlegm-Heat. Both herbs appear together in Hai Zao Yu Hu Tang.

Ju He
Ju He 1:1 (equal amounts)

Hai Zao softens hardness and dissolves Phlegm nodules, while Ju He (tangerine seed) enters the Liver channel to move Qi, disperse cold, and relieve pain in the lower abdomen and scrotum. Together they address testicular swelling from both the Phlegm-mass side (Hai Zao) and the Qi stagnation/cold side (Ju He).

When to use: Testicular swelling, pain, or hernia conditions where Phlegm accumulation and Qi stagnation contribute to the mass and pain. Both appear together in Ju He Wan.

Key Formulas

These well-known formulas feature Hai Zao in a prominent role

Hai Zao Yu Hu Tang 海藻玉壶汤 King

The definitive formula for goiter and thyroid conditions, from the Ming dynasty text Wai Ke Zheng Zong (《外科正宗》). Hai Zao serves as King herb alongside Kun Bu and Hai Dai, directly showcasing its core action of softening hardness and dissolving Phlegm nodules in the neck. The formula is named after Hai Zao itself, underscoring its central role. Clinically used for thyroid nodules, simple goiter, thyroid adenoma, and breast lumps.

Ju He Wan 橘核丸 Assistant

From the Song dynasty Ji Sheng Fang (《济生方》), this formula treats testicular swelling, hernia, and scrotal pain. Hai Zao serves as an Assistant alongside Kun Bu and Hai Dai, providing the salty, softening action that dissolves the Phlegm nodules and hardened swellings in the lower body. This showcases Hai Zao's application beyond the neck, demonstrating its broader capacity to address Phlegm masses wherever they occur.

Comparable Ingredients

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

Kun Bu
Hai Zao vs Kun Bu

Both are salty, cold marine products that soften hardness, dissolve Phlegm, and reduce edema, and they are almost always used together. The key difference is that Hai Zao enters the Liver channel more strongly and is considered superior for softening hardness and dispersing clumps (especially goiter and testicular swelling), while Kun Bu is thought to be slightly stronger at promoting water metabolism. In practice, choosing one without the other is uncommon; they work best as a pair.

E Jiao
Hai Zao vs E Jiao

Both are salty and cold with Phlegm-dissolving and hardness-softening properties. However, Hai Zao enters the Liver channel and is stronger at softening hardness and dispersing clumps, making it better for goiter, testicular swelling, and hepatosplenomegaly. Ge Qiao (Clam Shell) enters the Lungs more strongly and is better at cooling the Lungs and descending Phlegm-Heat, making it more appropriate for cough and chest pain due to Phlegm-Fire.

Xia Ku Cao
Hai Zao vs Xia Ku Cao

Both treat scrofula and goiter, but through different mechanisms. Hai Zao is salty and cold, working primarily by softening hardness and dissolving Phlegm. Xia Ku Cao is acrid, bitter, and cold, working primarily by clearing Liver Fire and dispersing Qi stagnation. Hai Zao is the better choice when nodules are hard and well-defined (Phlegm predominant), while Xia Ku Cao is preferred when Liver Fire signs are prominent (irritability, red eyes, headache). They are frequently combined for comprehensive coverage.

Common Substitutes & Adulterants

Related species and common adulterations to be aware of when sourcing Hai Zao

Hai Zao is sometimes confused with Kun Bu (昆布, Ecklonia/Laminaria), another marine herb used for goiter and nodules. While both are often prescribed together, they come from different algae families and have distinct appearances: Kun Bu consists of flat, ribbon-like fronds (kelp), whereas Hai Zao has branching, bushy thalli with visible air bladders. The two official source species of Hai Zao themselves are sometimes not distinguished: large-leaf Hai Zao (Sargassum pallidum) and small-leaf Hai Zao (Sargassum fusiforme) have somewhat different morphology but are both accepted by the Chinese Pharmacopoeia. Large-leaf has spiny protrusions and broader leaves; small-leaf lacks spines and has narrower, strip-shaped leaves with spindle-shaped air bladders. Other Sargassum species not listed in the Pharmacopoeia may occasionally be mixed in as adulterants, particularly in coastal areas where multiple species grow together. Always verify the characteristic morphological features described above.

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

Toxicity Classification

Classical Chinese pharmacopoeia toxicity rating for Hai Zao

Non-toxic

The Yao Xing Lun and Ben Cao Hui Yan both describe Hai Zao as having "slight toxicity" (有小毒), though the current Chinese Pharmacopoeia does not classify it as toxic. The main safety concern relates to its high iodine content: excessive or prolonged intake can disrupt thyroid function, particularly in individuals with pre-existing thyroid conditions. Alginate sodium (藻胶酸钠), a component of Hai Zao, has shown toxicity in animal studies when injected intraperitoneally in mice, but oral administration at standard dosages is generally safe. The Ben Cao Bian Du warns that overuse of salty-cold substances like Hai Zao can cause blood stagnation and decline of vitality over time.

Contraindications

Situations where Hai Zao should not be used or requires extra caution

Avoid

Incompatible with Gan Cao (Glycyrrhiza/Licorice) according to the classical Eighteen Incompatibilities (十八反). Combined use may reduce therapeutic efficacy or increase toxicity. Avoid concurrent use unless under expert supervision.

Caution

Spleen and Stomach deficiency-cold (脾胃虚寒) with internal dampness. Hai Zao is bitter, salty, and cold in nature, which can further damage already weakened digestive function.

Caution

Hyperthyroidism (甲亢). Hai Zao is rich in iodine, which can worsen hyperthyroid conditions. People with overactive thyroid should avoid this herb.

Caution

Pregnancy. The cold nature and blood-moving properties of Hai Zao may be unsuitable during pregnancy. Use with caution or avoid.

Avoid

Iodine allergy or sensitivity. As a marine algae rich in iodine, individuals with known iodine allergies should not use Hai Zao.

Classical Incompatibilities

Traditional Chinese pharmacological incompatibilities — herbs or substances to avoid combining with Hai Zao

Hai Zao is one of the four herbs listed as incompatible with Gan Cao (甘草, Licorice) in the Eighteen Incompatibilities (十八反): "藻戟遂芫俱战草" — Hai Zao (海藻), Da Ji (大戟), Gan Sui (甘遂), and Yuan Hua (芫花) all oppose Gan Cao. This prohibition originates from the Shen Nong Ben Cao Jing and was formalized in the Eighteen Incompatibilities verse recorded in Zhang Congzheng's Ru Men Shi Qin (《儒门事亲》). Combined use is traditionally held to reduce efficacy or increase toxicity. However, this remains debated: some classical formulas (such as Hai Zao Yu Hu Tang) deliberately combine both herbs, and modern animal studies have shown mixed results regarding actual toxicity.

Special Populations

Important considerations for pregnancy, breastfeeding, and pediatric use

Pregnancy

Use with caution during pregnancy. Hai Zao is cold in nature with properties that promote water metabolism and disperse accumulations. While not explicitly listed as a major pregnancy-prohibited herb, its cold and dispersing nature could potentially disturb fetal stability. Its high iodine content is also a concern, as excessive iodine intake during pregnancy can affect fetal thyroid development. Classical sources such as the Ben Cao Hui Yan note its "slight toxicity." Pregnant women should avoid this herb unless specifically prescribed by an experienced practitioner.

Breastfeeding

Safety data specific to breastfeeding is limited. The high iodine content of Hai Zao is the primary concern, as iodine passes readily into breast milk. Excessive maternal iodine intake can affect the infant's thyroid function. Its cold nature may also theoretically affect milk quality for mothers with weak digestion. Use only under practitioner guidance during breastfeeding, and keep dosages conservative if prescribed.

Children

No specific pediatric dosage guidelines are established in classical or modern TCM texts for Hai Zao. Due to its cold nature and iodine content, use in children should be conservative and only under practitioner supervision. Dosages should generally be reduced to one-third to one-half of the adult dose depending on the child's age and weight. Not recommended for young children with weak digestion or Spleen-Stomach deficiency.

Drug Interactions

If you are taking pharmaceutical medications, be aware of these potential interactions with Hai Zao

Thyroid medications: Hai Zao is rich in iodine and may interfere with thyroid hormone medications (levothyroxine) or anti-thyroid drugs (methimazole, propylthiouracil). Its iodine content can alter thyroid hormone levels, potentially counteracting the effects of these medications.

Anticoagulant/antiplatelet drugs: Early research suggested that degraded alginate compounds from seaweed may have mild anticoagulant properties. Concurrent use with warfarin, heparin, or antiplatelet medications should be monitored, though clinical significance at standard herbal doses is unclear.

Antihypertensive drugs: Animal studies show that larger doses of Hai Zao can lower blood pressure. Concurrent use with antihypertensive medications may have an additive hypotensive effect.

Lithium: As with other iodine-rich substances, Hai Zao may theoretically interact with lithium, which affects thyroid function and iodine metabolism.

Dietary Advice

Foods and dietary considerations when taking Hai Zao

During treatment with Hai Zao, avoid foods and herbs that contain Gan Cao (Licorice), including herbal teas and confections that commonly include licorice. Reduce intake of excessively cold or raw foods to protect Spleen and Stomach function, as Hai Zao is already cold in nature. People with hypothyroidism being treated with Hai Zao for its iodine content should maintain a balanced diet and not consume excessive amounts of other iodine-rich foods (such as kelp or iodized salt) simultaneously. Those with hyperthyroid conditions should avoid Hai Zao and other high-iodine foods entirely.

Botanical Description

Physical characteristics and morphology of the Hai Zao source plant

Hai Zao is derived from two species of brown algae in the Sargassaceae family. Sargassum pallidum (海蒿子, "large-leaf Hai Zao") is a coarse, leathery, yellowish-brown to olive-colored perennial alga that can grow 0.3 to 2.5 meters tall. It has a cylindrical main axis with bilateral, alternately arranged primary branches. The leaf-like phylloids vary greatly in shape, from broadly lanceolate near the base (up to 10 cm long with a distinct midrib) to small and linear in upper portions. Stalked, spherical air bladders (vesicles) develop in the middle portion of the thallus, and cylindrical reproductive receptacles grow in racemose clusters. The holdfast is discoid, anchoring to rocky substrates in the lower intertidal and upper subtidal zones.

Sargassum fusiforme (羊栖菜, "small-leaf Hai Zao") is a smaller, fleshy, yellow perennial alga, 7 to 40 cm tall. Its holdfast is fibrous and root-like. The main axis is cylindrical and erect (2–4 mm diameter), giving rise to short branches and club-shaped phylloids (3.5–7 cm long) with shield-shaped tips that sometimes swell into hollow air bladders. Spindle-shaped vesicles (5–10 mm) and cylindrical to elliptical reproductive receptacles (5–15 mm) arise from leaf axils. Both species grow attached to rocks in shallow, wave-battered coastal waters.

Sourcing & Harvesting

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

Harvesting season

Summer and autumn, harvested by gathering or cutting from the sea

Primary growing regions

Large-leaf Hai Zao (Sargassum pallidum): primarily distributed along the Yellow Sea and Bohai Sea coasts of Liaoning and Shandong provinces. Small-leaf Hai Zao (Sargassum fusiforme): more widely distributed along the coasts of Liaoning, Shandong, Fujian, Zhejiang, and Guangdong provinces. Shandong and Fujian are considered the primary producing regions. The best medicinal quality traditionally comes from the Shandong coastal region.

Quality indicators

Good quality Hai Zao should be dark blackish-brown in color with minimal white salt encrustation (盐霜). The branches should be young and tender, without sand, stones, or other debris mixed in. When moistened, the herb should become soft, fleshy, and slippery (粘滑). The smell should be distinctly fishy (腥), and the taste should be mildly salty. For large-leaf Hai Zao (大叶海藻): look for intact pieces 30-60 cm long with visible lance-shaped leaves, spherical black-brown air bladders, and short spiny protrusions on the main axis. For small-leaf Hai Zao (小叶海藻): pieces are smaller (15-40 cm), with strip-shaped or narrow spoon-shaped leaves, spindle-shaped air bladders on longer stalks, and no spiny protrusions. The texture should be somewhat harder than the large-leaf variety. Per Pharmacopoeia standards: moisture content should not exceed 19.0%, and alcohol-soluble extractives should be no less than 6.5%.

Classical Texts

Key passages from the classical Chinese medical texts that describe Hai Zao and its therapeutic uses

Shen Nong Ben Cao Jing (《神农本草经》)

Original: 主瘿瘤气，颈下核，破散结气，痈肿癥瘕坚气，腹中上下鸣，下十二水肿。

Translation: "Treats goiter-Qi, nodes below the neck, breaks and disperses knotted Qi, abscesses, masses, and hard accumulations, rumbling in the abdomen, and resolves the twelve types of water swelling."

Ming Yi Bie Lu (《名医别录》)

Original: 疗皮间积聚，暴癀，留气，热结，利小便。

Translation: "Treats accumulations between the skin, sudden swelling, retained Qi, Heat binding, and promotes urination."

Yao Xing Lun (《药性论》)

Original: 治气痰结满，疗疝气下坠，疼痛核肿，去腹中雷鸣，幽幽作声。

Translation: "Treats fullness from Qi-Phlegm binding, hernia with downward bearing and pain, nodular swelling, and eliminates rumbling and gurgling sounds in the abdomen."

Ben Cao Meng Quan (《本草蒙筌》)

Original: 治项间瘰疬，消颈下瘿囊，利水道，通癃闭成淋，泻水气，除胀满作肿。

Translation: "Treats scrofula between the neck, dissolves goiter below the neck, promotes the water pathways, opens urinary blockage and strangury, drains water-Qi, and eliminates distension and swelling."

Historical Context

The history and evolution of Hai Zao's use in Chinese medicine over the centuries

Hai Zao was first recorded in the Shen Nong Ben Cao Jing (Divine Farmer's Classic of Materia Medica), where it was listed as a middle-grade (中品) herb, primarily indicated for goiter and dispersing nodules. The name "海藻" literally means "sea algae," reflecting its marine origin. In the Er Ya, one of the oldest Chinese dictionaries, it was called "蒋" (jiǎng), and the Ben Jing called it "落首" (luò shǒu).

The herb holds a famous place in TCM history because of its role in the Eighteen Incompatibilities (十八反). The well-known verse "藻戟遂芫俱战草" ("Sargassum, Spurge, Kansui, and Daphne all war with Licorice") from Zhang Congzheng's Ru Men Shi Qin (Confucians Dutiful to Their Parents, Jin-Yuan period) codified this prohibition. However, the relationship is debated: Li Shizhen noted that Li Dongyuan used Hai Zao and Gan Cao together in his formula for scrofula, arguing that stubborn, hard diseases require opposing forces to achieve results. The famous formula Hai Zao Yu Hu Tang (Sargassum Jade Flask Decoction) from Yi Zong Jin Jian deliberately combines Hai Zao with Gan Cao to treat goiter, representing a deliberate application of "opposing forces working together" (相反相成).

The Ben Cao Shi Yi (Supplement to Materia Medica) by Chen Cangqi made an important distinction between two types: the small "horse-tail" variety found in shallow water and the large-leaf variety harvested from deep ocean. He noted that divers would tie ropes around their waists and descend to the ocean floor to cut it, but warned against harvesting after the fifth month due to the danger of large fish attacking.

Modern Research

4 published studies investigating the pharmacological effects or clinical outcomes of Hai Zao

1

Review: Composition, isolation, purification and biological activities of Sargassum fusiforme polysaccharides (2020)

Zhang R, Zhang X, Tang Y, Mao J. Carbohydrate Polymers, 2020, 228:115381.

A comprehensive review summarizing that S. fusiforme polysaccharides are mainly composed of alginic acid, fucoidan, and laminaran. These compounds demonstrate antioxidant, anti-tumor, immune-boosting, anti-aging, blood sugar-lowering, anti-coagulation, and antibacterial activities. Fucoidan was highlighted as the most biologically active component.

DOI
2

Preclinical study: Antitumor and immunomodulatory activity of polysaccharides from Sargassum fusiforme (2012)

Chen X, Nie W, Yu G, Li Y, Hu Y, Lu J, Jin L. Food and Chemical Toxicology, 2012, 50(3-4):695-700.

Polysaccharides from S. fusiforme (SFPS) were tested in mice inoculated with A549 lung cancer cells. Oral administration at 100 and 200 mg/kg for 28 days showed significant anti-tumor effects and enhanced immune responses including increased TNF-alpha levels and splenocyte proliferation.

DOI
3

Preclinical study: Sargassum fusiforme polysaccharide partly replaces acarbose against type 2 diabetes in rats (2021)

Li ZR, Jia RB, Wu J, Lin L, Ou ZR, Liao B, Zhang L, Zhang X, Song G, Zhao M. International Journal of Biological Macromolecules, 2021, 170:447-458.

S. fusiforme polysaccharide (SFP) co-administered with low-dose acarbose showed better anti-diabetic effects than acarbose alone in rats, including improved fasting blood glucose control, reduced insulin resistance, decreased kidney injury, and restored beneficial gut flora composition.

DOI
4

Review: Recent advances of Sargassum pallidum in chemical and biological aspects (2025)

Recent advances of Sargassum pallidum in chemical and biological aspects. PMC article, 2025.

A review identifying polysaccharides, flavonoids, and lipids as the primary metabolites of S. pallidum. Extracts demonstrated antioxidant, antitumor, hypolipidemic, hypoglycemic, antibacterial, and immunomodulatory activities in various experimental models.

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.