Hai Dai (Kelp, Laminaria Thallus)

Chinese Herb Actions

Chinese Herb Dosage

• What is the typical dosage of Hai Dai?

  Roughly 6–15 g in decoction, the same working range given for its near-twin Kun Bu. Standard materia medica references differ slightly at the low end, some giving about 6–15 g and others about 10–15 g. The part used is the dried thallus, the whole flattened blade of the kelp, and it is almost always combined with other phlegm-softening and hardness-dispersing herbs rather than used alone.

  • 6–15 g in decoction is the commonly cited range.
  • 10–15 g at the higher end in some references.
  • Part used: dried thallus (blade) of the kelp.

  Source: Sacred Lotus sources & references; standard materia medica dosage ranges (Bensky & Barolet; Chen & Chen). Reference only — not a prescription.

Chinese Herb Contraindications & Cautions

• Are there cautions for Hai Dai?

  Use with caution where there is Spleen and Stomach deficiency with cold — Hai Dai is a cold, salty, draining sea vegetable and can burden weak or cold digestion. Two modern reference points also matter, and both concern what kelp draws from seawater: iodine and heavy metals.

  • Thyroid conditions — Hai Dai is kombu, among the most iodine-dense foods known. Controlled feeding of kombu (Laminaria japonica) at 15–30 g/day for 7–10 days significantly raised serum TSH in healthy Japanese adults, in some cases above the normal range, reversing after the seaweed was stopped (PMID 18689954). Anyone with a thyroid condition, or taking thyroid medication, should use Hai Dai only under qualified practitioner supervision.
  • Arsenic / heavy metals — kelp bioaccumulates metals from seawater. A Chinese assessment found Laminariae Thallus samples exceeding international heavy-metal limits (PMID 32237335), and a large survey of 10,245 Chinese herbal medicine samples placed Eckloniae/Laminariae thallus among the herbs at high risk of arsenic contamination (PMID 33516113). This is a sourcing and quality-control point — tested material matters.
  • Pregnancy and breastfeeding — because of the iodine load, professional supervision is appropriate; this is a precautionary reference note.

  Source: Sacred Lotus sources & references (traditional cautions); PMID 18689954, PMID 32237335, PMID 33516113. Neutral reference facts, not usage instructions.

Chinese Herb Toxicity & Overdose

• Low intrinsic toxicity. Hai Dai (kombu) is an everyday food kelp with a long dietary history in East Asia and no significant toxicity reported at normal culinary or medicinal amounts. The documented concerns are not intrinsic toxicity but accumulated substances: iodine, which can measurably shift thyroid function at high sustained intake (PMID 18689954), and environmental contaminants, with arsenic and other heavy metals identified in Laminariae/kelp thallus samples (PMID 32237335, PMID 33516113). Total iodine in edible seaweeds varies widely by species and harvest, and whether a given sample is judged safe can depend on which national standard is applied (PMID 40870777).

  Sources: PMID 18689954; PMID 32237335; PMID 33516113; PMID 40870777. Reference note, not a safety guarantee.

Herb-Drug Interactions

• No well-established clinical herb–drug interactions are documented for Hai Dai, but two precautionary areas deserve practitioner awareness. First, thyroid medication: Hai Dai is a high-iodine kelp, and iodine from kombu can measurably alter thyroid function tests in healthy adults (PMID 18689954), so concurrent use with levothyroxine, antithyroid drugs, or radioactive-iodine protocols warrants professional oversight. Second, anticoagulant and antiplatelet drugs: fucoidan isolated from Laminaria japonica has shown antithrombotic and antiplatelet activity in animal models (PMID 21872298). That is a finding about an isolated, purified polysaccharide, not a demonstrated interaction of the whole decocted herb, but it is a reasonable flag alongside warfarin, heparin, or antiplatelet therapy. (Both precautionary; confirm with a qualified practitioner.)

  Sources: PMID 18689954; PMID 21872298. Precautionary reference, not a documented clinical interaction.

Western / Biomedical Research

Chinese Herb Clinical Studies & Research

Provided as research context — a summary of published biomedical study, not a therapeutic or medical claim.

• Is there modern research on Hai Dai (kelp) and its traditional use for goiter?

  Yes — and iodine is the obvious modern explanation for the classical goiter use, though probably not the whole story. Hai Dai is Laminaria japonica, one of the most iodine-rich foods known, which makes the centuries-old use for goiter chemically plausible. But iodine excess also disturbs the thyroid, so the same constituent that explains the traditional use is the reason for modern caution. We carry both facts rather than a tidy single story.

  • Iodine content is high and variable — analysis of 348 seaweed samples across five species found wide variation in total iodine, with sea tangle (kelp) the highest of those tested; risk assessments changed depending on which international standard was applied (PMID 40870777).
  • Iodine measurably moves thyroid function — 15–30 g/day of kombu (Laminaria japonica) for 7–10 days significantly raised serum TSH in healthy adults, with levels reversing after stopping (PMID 18689954). This is a direct study of the same seaweed sold as Hai Dai.
  • Polysaccharide pharmacology — fucoidan from Laminaria japonica showed antithrombotic and antiplatelet activity in rats (PMID 21872298), and Laminaria japonica polysaccharides lowered total cholesterol, triglycerides, and LDL while raising HDL in mice with induced diabetes (PMID 24928865). These are isolated-compound and animal studies, not clinical evidence for the decocted herb.

  Overall: the traditional goiter indication has a plausible modern chemical rationale in iodine, but iodine is also why kelp can suppress the thyroid, and the roles of kelp's non-iodine constituents remain open in the literature. None of this is evidence that Hai Dai treats thyroid disease.

  Identity note: Hai Dai (海带) and Kun Bu (昆布) overlap in the sources. In the Chinese Pharmacopoeia the medicinal drug “Kun Bu” is the dried thallus of Laminaria japonica or Ecklonia kurome, and Hai Dai is the common name for Laminaria japonica (kombu) specifically — so Hai Dai is one of the two plants that make up official Kun Bu. Older materia medica sometimes treat Hai Dai and Kun Bu as a single entry and sometimes separate them. Sacred Lotus keeps two records and splits the dual botanical source between them: this Hai Dai record as Laminaria japonica, and the existing Kun Bu record as Ecklonia kurome. Note also that Laminaria japonica is now often reclassified as Saccharina japonica. Readers comparing sources should expect either binomial, and should expect iodine and contaminant load to differ meaningfully between source species and harvest areas (PMID 40870777).

  Sources: PMID 40870777 (Foods, 2025, total iodine in edible seaweeds); PMID 18689954 (Endocrine Journal, 2008, kombu / Laminaria japonica and thyroid function); PMID 21872298 (Thrombosis Research, 2012, Laminaria japonica fucoidan antithrombotic/antiplatelet, rats); PMID 24928865 (Experimental Biology and Medicine, 2014, Laminaria japonica polysaccharides, hypolipidemic/hypoglycemic in diabetic mice); PMID 32237335 (heavy metals in Laminariae Thallus); PMID 33516113 (Journal of Hazardous Materials, 2021, arsenic risk in Eckloniae/Laminariae thallus). Research context, not a therapeutic claim.

Chinese Herb Notes

• What is the difference between Hai Dai and Kun Bu?

  They are almost the same medicine — both are salty, cold kelps in the same category that soften hardness and dissolve phlegm for goiter and nodules, and the names overlap in the pharmacy. In the Chinese Pharmacopoeia the drug “Kun Bu” (昆布) is defined as the dried thallus of Laminaria japonica or Ecklonia kurome. Hai Dai (海带) is the everyday name for Laminaria japonica, the food kelp (kombu), which is one of those two official Kun Bu source species. Hai Dai is therefore less a different herb from Kun Bu than one of the plants Kun Bu is made from.

  • Hai Dai (海带) — Laminaria japonica (now often placed in Saccharina); the broad, ribbon-like food kelp, kombu.
  • Kun Bu (昆布) — the pharmacy name for kelp thallus; officially Laminaria japonica or Ecklonia kurome. Sacred Lotus's existing Kun Bu record gives the Latin as Ecklonia kurome, so our two records split the dual source between the species.
  • Shared ground — salty, cold; Liver, Stomach, Kidney; goiter, scrofula, phlegm nodules; both are iodine-rich brown algae (see research and cautions below).

  Which formula is Hai Dai best known in?

  Its best-known home is Hai Zao Yu Hu Tang (Sargassum Decoction for the Jade Flask), the classic goiter formula from Wai Ke Zheng Zong, where Hai Dai joins Hai Zao and Kun Bu as the three-seaweed core — alongside Zhe Bei Mu, Ban Xia, Chen Pi, Qing Pi, Lian Qiao, Dang Gui, Chuan Xiong, Du Huo and Gan Cao. The three marine herbs are used together rather than chosen between; Hai Dai is the third of the trio.

  (Traditional formula context, not treatment advice.)

  Source: Sacred Lotus sources & references (herb identity and formula composition data for Hai Zao Yu Hu Tang), cross-referenced against multiple online sources, the Chinese Pharmacopoeia definition of Kun Bu, and materia medica consensus.