Last verified: 37 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, Eversmithorganics, Secret Element Sea Moss 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
Eversmithorganics
Supplement
Secret Element Sea Moss
Supplement
NaturaLife Labs Organic Ashwagandha 2100 mg
Supplement
Infinite Age Sea Moss Advanced Capsules
Supplement
Secret Element Sea Moss + Black Seed Oil 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