Last verified: 17 days ago
Bladderwrack
Also known as: Fucus vesiculosus, brown kelp, rockweed, sea oak
Evidence under review. — Not yet rated
Brown seaweed with very early-stage research on hormonal effects. Evidence is extremely limited.
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What it does
Bladderwrack is an edible brown seaweed (Fucus vesiculosus) that has been used in traditional medicine for centuries. A very small pilot study in three pre-menopausal women found that taking...
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Evidence quality
Evidence base hasn't been formally rated yet. See research below.
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Clinical dose
No established dose (insufficient research data)
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Found in
Snap Supplements Irish Sea Moss, NaturaLife Labs Organic Ashwagandha 2100 mg, Eversmithorganics and 3 more
What the Science Says
Bladderwrack is an edible brown seaweed (Fucus vesiculosus) that has been used in traditional medicine for centuries. A very small pilot study in three pre-menopausal women found that taking 700–1400 mg per day was associated with longer menstrual cycles and reduced estrogen levels. Lab-based screening also identified it as having some anti-mitotic (cell-division-blocking) activity against breast cancer cells, though this was a test-tube study only and has no proven relevance to humans.
What It Doesn't Do
Not proven to treat or prevent cancer in humans — the lab result is extremely preliminary. No solid evidence it balances hormones reliably. Not a proven thyroid supplement despite common marketing claims. No human data on weight loss, detox, or metabolism benefits.
Evidence-Based Benefits
May lengthen menstrual cycles in pre-menopausal women with irregular periods.
Weak EvidenceEffective at: 700–1400 mg/day
Supporting studies (click to view on PubMed):
Associated with reduced estradiol levels in a small pilot study of pre-menopausal women.
Weak EvidenceEffective at: 700–1400 mg/day
Supporting studies (click to view on PubMed):
Absorption & Bioavailability
Unknown — no pharmacokinetic data available from the provided studies for human oral absorption
Red Flags to Watch For
- Bladderwrack is a marine algae that can accumulate heavy metals, organotin compounds (like tributyltin), and radioactive elements from polluted coastal waters — contamination is a real concern
- The only human hormone data comes from a case report of just 3 women — this is not enough evidence to draw conclusions
- May significantly alter estrogen and progesterone levels, which could be dangerous for people with hormone-sensitive conditions or those on hormonal medications
- Iodine content in seaweed can be highly variable and may trigger or worsen thyroid disorders
- No safety profile established from the provided studies for long-term use
Products Containing Bladderwrack
See how Bladderwrack is used in these analyzed products:
Snap Supplements Irish Sea Moss
Supplement
NaturaLife Labs Organic Ashwagandha 2100 mg
Supplement
Eversmithorganics
Supplement
Secret Element Sea Moss
Supplement
Secret Element Sea Moss + Black Seed Oil Capsules
Supplement
Infinite Age Sea Moss Advanced Capsules
Supplement
Frequently Asked Questions
What does Bladderwrack do?
Brown seaweed with very early-stage research on hormonal effects. Evidence is extremely limited.
What is the effective dose of Bladderwrack?
No established dose (insufficient research data)
Is Bladderwrack safe?
Bladderwrack is a marine algae that can accumulate heavy metals, organotin compounds (like tributyltin), and radioactive elements from polluted coastal waters — contamination is a real concern
What doesn't Bladderwrack do?
Not proven to treat or prevent cancer in humans — the lab result is extremely preliminary.
Research Sources
- PubMed
- NIH DSLD
This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-05-25