Bladderwrack
Also known as: Fucus vesiculosus, brown kelp, rockweed, sea oak
Effective Dosage
No established dose (insufficient research data)
What the Science Says
Bladderwrack is an edible brown seaweed (Fucus vesiculosus) harvested from Atlantic coastlines. One very small case report involving only three women suggested it may lengthen menstrual cycles and reduce estrogen levels, possibly by affecting sex hormone biosynthesis. A lab-based screen also found bladderwrack extract showed some anti-mitotic (cell-division-blocking) activity against breast cancer cells in a dish, though this is far from human evidence.
What It Doesn't Do
Not proven to treat or prevent cancer in humans — lab dish results mean almost nothing clinically. No solid evidence it supports thyroid health, promotes weight loss, or detoxifies the body. The hormone effects seen in three women cannot be generalized to anyone. Don't assume 'seaweed' equals safe or effective.
Evidence-Based Benefits
Bladderwrack is a type of seaweed that is often used in traditional medicine for its potential benefits, including thyroid support due to its iodine content. Some studies suggest it may have antioxidant properties, but overall evidence is limited and inconsistent.
Weak EvidenceEffective at: Unknown (insufficient research data)
Source: auto-research
Absorption & Bioavailability
Unknown — no pharmacokinetic data from the provided studies on bladderwrack in humans
Red Flags to Watch For
- May contain heavy metals and organotin compounds (like tributyltin) absorbed from ocean water — contamination is a real concern
- Can accumulate environmental pollutants including polonium-210 and aluminum from coastal waters
- Anti-estrogenic effects could be dangerous for women on hormone therapies or with hormone-sensitive conditions
- Only one human study exists — a case report of 3 women — making any health claims highly speculative
- Widely sold (1000+ registered products) despite almost no clinical evidence supporting its use
Products Containing Bladderwrack
See how Bladderwrack is used in these analyzed products:
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: 2026-04-06