Kun Bu
StarLaminaria japonica Aresch. / Ecklonia kurome Okam.
Traditionally used for
- Cough & breathing
- Digestion
- Urinary & fluids
Cautions & contraindications
- Bleeding disorders
☯ TCM Properties
Dissipates Nodules and Softens Hardness; Resolves Phlegm; Promotes Urination and Reduces Edema
Traditional Chinese Uses
Kun Bu (kelp thallus) is a cold, salty herb that softens hardened masses and dissipates phlegm-related nodules — making it the herb of choice for goiter, thyroid swellings, lymph node enlargement, and other firm swellings. Its ability to drain fluid accumulation is also applied to abdominal masses and edema. Rich in iodine, its traditional use for goiter aligns with its known contribution to thyroid function.
Western Herbalism Properties
Relationships
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Botanical Description
Laminaria japonica J.E.Areschoug (now often placed in Saccharina) and Ecklonia kurome Okamura are large brown marine algae in the order Laminariales (Laminariaceae), both of which are used interchangeably as the source of Kun Bu. Laminaria japonica forms a long, leathery, ribbon-like blade typically 2 to 6 meters long and 20 to 50 cm wide, with a smooth, undivided lamina, a short stipe and a branched, root-like holdfast that anchors it to subtidal rocks in cold temperate waters along the coasts of northern China, Korea and Japan. Ecklonia kurome is smaller, with a digitately divided blade and a tougher, more cartilaginous texture. Both species are harvested, washed and sun-dried, producing dark olive-green to nearly black, leathery sheets that are folded or shredded for medicinal and culinary use. As a non-vascular marine alga the thallus has no true roots, stems or leaves; the entire dried thallus is used in traditional Chinese medicine.
Active Constituents
Iodine
Halogen trace element, present as iodide and iodinated organic compoundsConcentration: The dominant safety-relevant constituent. In a UK survey of commercial edible algae by ICP-MS, macroalgae averaged 1,925.01 plus or minus 1,455.80 mg/kg iodine against 17.61 plus or minus 34.87 mg/kg in microalgae. EFSA identified mean intakes above 20 micrograms per kilogram body weight per day among consumers-only of Kombu and Laver, which is the highest of any food group assessed
Iodine at these concentrations does not behave like a nutrient. A large bolus can shut thyroid hormone synthesis down through the acute Wolff-Chaikoff effect and produce hypothyroidism, or, in a nodular or autonomous gland, drive iodine-induced hyperthyroidism. Both have been reported from kelp products in patients with no previous thyroid disease. The dose delivered by a given weight of thallus is not predictable: iodine content varies more than 75 per cent about its own mean across commercial material, and labelling of iodine content is frequently absent.
Arsenic
Metalloid, present largely as arsenosugars with a variable inorganic arsenic fractionConcentration: Eight of nine kelp supplements sampled at random from Californian health-food stores exceeded the US FDA tolerance of 0.5 to 2 ppm for total arsenic in certain foods, the implicated product at 8.5 mg/kg. EFSA identifies seaweeds as an important source of total arsenic, mainly organic, and estimates seaweed at 10 to 30 per cent of previously estimated whole-diet inorganic arsenic exposure in European adults
Brown algae concentrate arsenic from seawater. Most of it is arsenosugars rather than the inorganic arsenite and arsenate that carry the classical toxicity, and a published rebuttal to the index case report argued exactly that: regulatory limits apply to inorganic arsenic, and a total-arsenic figure overstates the hazard. That rebuttal does not dispose of the problem. Arsenosugars are metabolised in humans to dimethylarsinic acid and excreted, inorganic arsenic is present at variable and species-dependent levels, and a controlled human feeding study found urinary total arsenic rose measurably after Kombu. Speciated assay, not a total-arsenic number, is what settles the question for a given batch.
Sodium alginate
Alginate polysaccharide, a block copolymer of mannuronic and guluronic acidConcentration: The bulk structural polysaccharide of the thallus and the largest single fraction of the dry drug
Forms a viscous gel in gastric acid and binds divalent cations. This is the basis of its pharmaceutical use as a reflux raft, and the reason a decoction taken alongside oral medication or mineral supplements can reduce their absorption by physical entrapment rather than by any pharmacological mechanism.
Fucoidan
Sulfated fucan polysaccharideConcentration: A characteristic sulfated polysaccharide of brown algae; content varies with species, season and harvest site
Anti-inflammatory and immunomodulatory in preclinical models. Its sulfated, heparin-like structure has long prompted concern about anticoagulant activity, but a 28-day rat study at 100, 150 and 200 mg/kg of brown-algal fucoidan found no significant change in prothrombin time, thrombin time or partial thromboplastin time, so the in vitro anticoagulant signal has not carried over to whole-animal haemostasis at those doses.
Laminarin
Beta-1,3-glucan storage polysaccharideConcentration: Storage glucan of Laminaria and Saccharina species, accumulating seasonally
Fermented by colonic bacteria and studied as a prebiotic and immunomodulator. No established clinical effect.
Fucoxanthin
Xanthophyll carotenoidConcentration: The pigment that gives the brown algae their colour
The constituent behind most of the metabolic-syndrome interest in this alga: it acts on lipid handling, AMP-activated protein kinase and acetyl-CoA carboxylase in animal models. The supporting evidence is animal and cell work, with human trials of the whole alga still absent.
Mannitol
Sugar alcoholConcentration: A major low-molecular-weight component of Laminaria and Saccharina thalli, and the white efflorescence seen on dried kombu
Osmotically active and poorly absorbed, so a large intake draws water into the gut lumen and can loosen stools.
⚠ Drug Interactions
Levothyroxine and liothyronine
The drug delivers an iodine load orders of magnitude above physiological requirement, and the thyroid response is not predictable from the dose. A 70-year-old woman with no previous thyroid disease developed transient hyperthyroidism three months after starting kelp tablets and needed three months of methimazole before thyroid function normalised on withdrawal; conversely, sustained heavy seaweed intake has produced primary hypothyroidism without thyroid autoantibodies, resolving on stopping the seaweed. In 44 habitual Norwegian macroalgae consumers median urinary iodine was 1,200 micrograms per litre, comfortably in the excessive range, with thyroid-stimulating hormone within reference but higher than in comparable groups. On top of the endocrine effect, the alginate fraction can bind levothyroxine in the gut lumen and reduce its absorption.
Clinical note: Do not add this drug to established thyroid replacement without measuring TSH and free T4 before and roughly six weeks after starting, and again on stopping. Separate any dose from levothyroxine by at least four hours. Treat new palpitations, weight change or fatigue in a kelp user as thyroid until disproved.
Antithyroid drugs (carbimazole, methimazole, propylthiouracil)
Antithyroid drugs work by blocking iodine organification. Supplying a very large iodine substrate load works against that and can prolong or destabilise treatment; in an autonomously functioning nodule or a multinodular goitre it can precipitate iodine-induced thyrotoxicosis outright. The kelp-associated hyperthyroidism case required antithyroid drug treatment for three months after the kelp was stopped, which is the shape of the problem: the iodine load outlasts the exposure.
Clinical note: Contraindicated during antithyroid treatment. Ask specifically about seaweed foods and kelp supplements, not just about herbs, when thyrotoxicosis fails to settle on treatment.
Radioiodine (iodine-131 therapy and diagnostic thyroid scintigraphy)
Radioiodine uptake depends on the thyroid being iodine-depleted, which is why a low-iodine diet is required before treatment or scanning. A drug that is among the most iodine-dense substances a patient can swallow saturates the sodium-iodide symporter and dilutes the tracer or therapeutic dose, producing a false-negative scan or an under-treated ablation. The effect persists for weeks after the last dose because the iodine pool is slow to clear.
Clinical note: Stop this drug and all seaweed foods at least several weeks before any radioiodine scan or ablation, and tell the nuclear medicine department it has been taken. This is a reason to take a seaweed history in every thyroid cancer and Graves patient.
Amiodarone
Amiodarone is itself an iodine-rich molecule and causes both amiodarone-induced hypothyroidism and thyrotoxicosis. Adding an iodine load of the magnitude that this drug supplies compounds the same mechanism on the same gland, and makes the already difficult distinction between type 1 and type 2 amiodarone-induced thyrotoxicosis harder still. The interaction is inferred from the shared mechanism rather than from a reported series.
Clinical note: Avoid in any patient on amiodarone or within twelve months of stopping it.
Lithium
Lithium inhibits thyroid hormone release and is a recognised cause of goitre and hypothyroidism. A large iodine load acts on the same gland through the Wolff-Chaikoff route, and the two are expected to add. The reasoning is mechanistic; no controlled data address the combination.
Clinical note: Check thyroid function before and during use in any lithium-treated patient, and prefer to avoid the combination.
Hai Zao (Sargassum) and other seaweed drugs
This drug and Hai Zao are routinely combined in the same nodule and goitre formulas, and both are iodine-dense arsenic-accumulating brown algae. The exposure is therefore additive while appearing on the prescription as two separate items with two separate doses. Sargassum fusiforme, one of the Hai Zao source species, is among the seaweeds with the highest inorganic arsenic content, so the arsenic half of the sum is not evenly shared.
Clinical note: Count total seaweed weight across the formula, not the individual herb dose, and count dietary seaweed too.
Orally administered drugs and mineral supplements taken at the same time
The alginate fraction is the bulk of the thallus and gels in gastric acid, binding divalent cations and physically entrapping co-ingested material. That is the property exploited in alginate reflux preparations. The consequence for a decoction taken with medication is reduced or delayed absorption, most consequentially for levothyroxine, iron, calcium and bisphosphonates.
Clinical note: Separate administration from other oral drugs and mineral supplements by at least two to four hours.
Warfarin, direct oral anticoagulants and antiplatelet drugs
Fucoidan is a sulfated polysaccharide structurally reminiscent of heparin and shows anticoagulant activity in vitro, which is the origin of the standard caution. When brown-algal fucoidan was given to rats for 28 days at 100 to 200 mg per kg, however, prothrombin time, thrombin time and partial thromboplastin time were unchanged. The concern is real in principle and unsupported in practice at herbal doses.
Clinical note: Record the caution but do not stop an anticoagulant over it. If both are used, monitor as you would anyway rather than assuming an interaction.
Arsenic trioxide and other arsenic exposures (contaminated well water, arsenic-rich seaweeds)
The alga carries an arsenic load, mostly organic but with a variable inorganic fraction, and human feeding data confirm that urinary total arsenic rises after Kombu. Where another arsenic source is present, whether therapeutic arsenic trioxide, contaminated drinking water or arsenic-rich seaweed, the exposures sum. Arsenic also acts additively with aristolochic acid in urothelial carcinogenesis, so an arsenic history matters in any patient who has also had aristolochic acid exposure.
Clinical note: Avoid during arsenic trioxide therapy. In long-term users, prefer material with a speciated inorganic arsenic assay, and take a drinking-water history where relevant.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| decoction | 6–12 g | Daily | — | — | 中国药典 2020 【用法与用量】6～12g。 【性味与归经】咸，寒。归肝、胃、肾经。 — Chinese Pharmacopoeia 2020, quoted verbatim; route and cautions preserved. Replaces a cleared category-filler value. |
Dui Yao — Herb Pairs
The classical two-herb combinations this herb appears in, each with an action neither herb has alone.
Mutually reinforce softening of hardness, dissipating of nodules and dispelling of phlegm, for goiter and scrofula.
Hai Zao is traditionally listed as incompatible with Gan Cao (shi ba fan).
Named pairing — Zhong Yao Xue national textbook, pei wu discussion
Evidence Tier
Strong evidence · 9 studiesRecorded studies by study design, strongest design at the top. This is a study-design tier only, not a GRADE rating: it does not weigh risk of bias, consistency or precision.
Systematic review / meta-analysis
2
1 verified · 1 unverified
Randomized controlled trial
0
Other clinical trial
0
Observational / case report
5
3 verified · 2 unverified
Show 5 studies
- Exposure to iodine, essential and non-essential trace element through seaweed consumption in humans
- Iodine Status and Thyroid Function in a Group of Seaweed Consumers in Norway
- Transient Hyperthyroidism following the ingestion of complementary medications containing kelp seaweed
- Hypothyroidism Due to Seaweed Overconsumption
- Case Report: Potential Arsenic Toxicosis Secondary to Herbal Kelp Supplement
In vitro / animal
1
0 verified · 1 unverified
Other / unclassified
1
0 verified · 1 unverified
Verified: design read from PubMed for a DOI that resolves to the cited paper Unverified: taken from the study's recorded description
Clinical Studies
Exposure to iodine, essential and non-essential trace element through seaweed consumption in humans
Controlled feeding intervention in 11 volunteers using Nori, Kombu and Wakame, with urinary total arsenic, cobalt, copper, cadmium, iodine, molybdenum, selenium and zinc measured before and after. Urinary iodine and total arsenic both rose after seaweed consumption. In the eight-element mixture analysis the largest weight was iodine after Kombu and total arsenic after Wakame. This is the direct human demonstration that eating this alga measurably raises both exposures.
Iodine Status and Thyroid Function in a Group of Seaweed Consumers in Norway
Forty-four habitual macroalgae consumers gave two urine samples each; 19 also gave serum. Median urinary iodine concentration was 1,200 micrograms per litre, with an interquartile range of 370 to 2,850, against an estimated dietary iodine intake excluding seaweed of only 110 micrograms per day, so the seaweed was supplying almost all of it. TSH stayed within reference but ran higher than in comparable populations. A third of participants ate seaweed daily, and iodine content was unlabelled on a large share of products.
Transient Hyperthyroidism following the ingestion of complementary medications containing kelp seaweed
A 70-year-old woman with no previous thyroid disease presented with tachycardia above 100 beats per minute, insomnia, anxiety and 6 kg of weight loss over three months, three months after starting kelp-containing slimming tablets. The tablets were stopped and methimazole given at 15 mg then 10 mg then 5 mg daily over three months, after which thyroid function normalised and remained normal. The case establishes that an intact thyroid with no prior disease is not protected.
Hypothyroidism Due to Seaweed Overconsumption
Primary hypothyroidism without thyroid autoantibodies traced to habitual excessive daily seaweed consumption taken for health. The report makes the point that matters clinically: when the iodine excess is a daily dietary habit rather than a supplement, patients do not connect it to their symptoms and will not volunteer it, so it has to be asked about directly.
Case Report: Potential Arsenic Toxicosis Secondary to Herbal Kelp Supplement
A 54-year-old woman with two years of worsening alopecia, memory loss, rash, fatigue, nausea and vomiting had a urine arsenic of 83.6 micrograms per gram creatinine against a normal below 50, and her daily kelp supplement assayed at 8.5 mg/kg arsenic. Symptoms resolved and blood and urine arsenic became undetectable within weeks of stopping. Eight of nine further kelp products bought at random from local health-food stores exceeded the FDA tolerance of 0.5 to 2 ppm, and none carried any heavy-metal warning. A published rebuttal noted the analysis measured total rather than inorganic arsenic; that qualifies the toxicological interpretation without removing the labelling problem.
Dietary exposure to heavy metals and iodine intake via consumption of seaweeds and halophytes in the European population
EFSA pooled 2,093 cadmium, 1,988 lead, 1,934 total arsenic, 920 inorganic arsenic, 1,499 total mercury and 1,002 iodine analytical results from 2011 to 2021 against 697 seaweed eating occasions in 468 subjects across 19 European countries. Cadmium exposure from seaweed alone approached previous whole-diet estimates; inorganic arsenic and lead reached 10 to 30 per cent of them. Arsenic in seaweed is mainly organic, with exceptions. Mean iodine intakes above 20 micrograms per kilogram body weight per day were found among consumers-only of Kombu and Laver, the highest identified.
The Effect of Laminaria japonica on Metabolic Syndrome: A Systematic Review of Its Efficacy and Mechanism of Action
Systematic review across PubMed, Web of Science, EMBASE and CENTRAL to September 2021 of clinical and in vivo studies of this species in metabolic syndrome. The retrievable evidence is dominated by animal work: reduced oxidative stress-related lipid handling, lower inflammatory cytokines and macrophage chemokines, glucosidase inhibition, raised AMP-activated protein kinase and lowered acetyl-CoA carboxylase in obesity models. The authors conclude the alga could be useful, which is a statement about mechanism rather than a demonstration of clinical benefit; controlled human trials remain sparse.
Nitrate, Nitrite, and Iodine Concentrations in Commercial Edible Algae: An Observational Study
Eighteen macroalgae and five microalgae species sold in the United Kingdom, with iodine by ICP-MS and nitrate and nitrite by HPLC. Macroalgae averaged 1,925.01 plus or minus 1,455.80 mg/kg iodine, more than a hundredfold the microalgal figure, with a standard deviation approaching the mean. That spread is the practical problem: a fixed weight of thallus does not deliver a fixed iodine dose.
Evaluation of the effects of fucoidan extracted from sargassum angustifolium on coagulation factors and biochemical parameters in male Wistar rats
Twenty-five rats in control, sham and three fucoidan groups at 100, 150 and 200 mg/kg for 28 days. Prothrombin time, thrombin time and partial thromboplastin time were unchanged, arguing against a clinically meaningful anticoagulant effect of orally administered fucoidan at these doses. Glucose fell dose-dependently and transferrin, iron and ferritin rose. The fucoidan came from Sargassum angustifolium, not from this alga, so it bears on the class question rather than on this drug specifically.
⚠ Safety & Contraindications
- Bleeding disorders
Contraindications
Its use is cautious in patients with deficiency-cold of the spleen and stomach and dampness stagnation.
Source: Xi S, Gong Y. Essentials of Chinese Materia Medica and Medical Formulas. Academic Press/Elsevier, 2017, pp. 267–277.
Historical Texts
Ming Yi Bie Lu
Period of Division, c. 500 CEXin Xiu Ben Cao
Tang dynasty, 659 CEBen Cao Gang Mu
Ming dynasty, 1596References
- Fabricant D. Arsenic in Herbal Kelp Supplements: Concentration, Regulations, and Labeling . Environmental Health Perspectives (2007) [DOI]
- Sim R, Weyer M, Petursdottir AH. Inorganic arsenic in seaweed: a fast HPLC-ICP-MS method without coelution of arsenosugars . Analytical and Bioanalytical Chemistry (2024) [DOI]
- EFSA Panel on Contaminants in the Food Chain (CONTAM), Knutsen HK, Akesson A, Bampidis V, Bignami M, Bodin L, Chipman JK, Degen G, Hernandez-Jerez A, Hofer T, Hogstrand C, Landi S, Leblanc JC, Machera K, Ntzani E, Rychen G, Sand S, Vejdovszky K, Viviani B, Barregard L, Benford D, Dogliotti E, Francesconi K, Gomez Ruiz JA, Steinkellner H, Schwerdtle T. Risk assessment of complex organoarsenic species in food . EFSA Journal (2024) [DOI]
- Yu LL, Browning JF, Burdette CQ, Caceres GC, Chieh KD, Davis WC, Kassim BL, Long SE, Murphy KE, Oflaz R, Paul RL, Sharpless KE, Wood LJ, Yen JH, Zeisler R. Development of a kelp powder (Thallus laminariae) Standard Reference Material . Analytical and Bioanalytical Chemistry (2018) [DOI]
This information is for educational purposes only and is not intended to replace professional medical advice. Always consult a qualified healthcare provider before using any herbal remedy, especially if you are pregnant, nursing, or taking medications.
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