Ecklonia bicyclis

BotanicalSeaweed

What is it

Ecklonia bicyclis (also classified as Eisenia bicyclis, 'arame') is a brown seaweed widely consumed in Japan and Korea. It is rich in iodine, fucoidan, alginate, and phlorotannins (such as dieckol and 8,8'-bieckol). It is closely related to Ecklonia cava, a more researched supplement source.

Evidence for 2 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Iodine nutrition

Strong Evidence

Seaweed is a major iodine source. Adequate iodine intake prevents goiter and supports thyroid hormone synthesis.

Cardiovascular / metabolic (phlorotannin extracts)

Limited Evidence

Small human studies of Ecklonia phlorotannin extracts (mostly E. cava) suggest modest improvements in blood pressure and lipid markers. Evidence for E. bicyclis specifically is limited.

How it works

Phlorotannins from Ecklonia species have shown antioxidant, anti-inflammatory, and mild blood pressure-lowering activity in animal studies, with effects attributed in part to ACE inhibition and modulation of NF-kB. Fucoidan has shown immunomodulatory and antithrombotic effects in preclinical studies. The seaweed is a substantial dietary iodine source - one of its most clinically relevant aspects for humans.

Dosage

There is no specific dose. Studies of Ecklonia cava extract (a related species) have used 100–500 mg/day. As food, traditional Japanese intake provides high iodine (potentially 1–3 mg/day, well above the 150 mcg RDA).

When and how to take it

As food with meals.

2 commercial forms

Compare the main delivery options and what they’re best suited for.

Whole seaweed (arame)

Traditional food form.

Iodine highly bioavailable; phlorotannins variable.

Phlorotannin-standardized extract

Supplement form.

Concentrated active fraction.

Safety

Iodine excess is the main concern with seaweed consumption, particularly in iodine-naive Western populations. Can trigger hypothyroidism or hyperthyroidism in susceptible individuals. Heavy metal contamination (especially arsenic, cadmium) is a quality concern for brown seaweed products.

Who should be cautious

Pregnancy: do not exceed the iodine UL (1,100 mcg/day). Thyroid disease patients should consult their endocrinologist. People on anticoagulants should be cautious with high-fucoidan products.

Interactions

Iodine content interacts with thyroid medications. Fucoidan has mild antiplatelet activity, with theoretical interaction with anticoagulants.

Food sources

Arame seaweed (dried, rehydrated)

Amount
Variable; high iodine
%DV
—

Frequently asked questions

Can I get too much iodine from seaweed?⌄

Yes. Heavy consumption of brown seaweed can deliver many times the iodine RDA and affect thyroid function.

Is Ecklonia bicyclis the same as Ecklonia cava?⌄

They are related species; most clinical research uses E. cava, and findings should not be assumed to transfer directly.

References

Ecklonia bicyclis on Wikidata — Wikidata link

Ecklonia bicyclis on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on Ecklonia bicyclis (PubMed search) — PubMed link

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.