Bladderwrack
Fucus vesiculosus
Sea Moss & Algae. Dr. Sebi's list and Western & European.
Also called Bladder wrack, Sea wrack, Rockweed, Black tang
Spanish: Fuco vesiculoso
High, variable iodineA brown seaweed with gas-filled bladders, sold for thyroid support and weight loss.
Did you know? Its gas-filled bladders keep it floating near the light. Coastal people once burned seaweeds like this to make kelp ash, a source of soda for soap and glass.
What it may help, and how strong the proof is
- Thyroid. Traditionally used for goiter from low iodine. No trials test it, and the right dose is unknown.Traditional proof
- Skin. One small study found that topical use made skin more elastic. More studies are needed.Traditional proof
- Women's health. Used for irregular periods. The only human report is a small study of three women.Traditional proof
- Weight. Sold for weight loss, but human studies show no lasting weight loss.Not supported
Parts of the body
Thyroid, Energy & metabolism, Skin & hair, Hormones & reproduction
Traditional use
On the Atlantic coasts of Europe and North America, it was used for goiter, a swollen thyroid linked to low iodine. Some folk healers also used it as an alterative, an old word for a blood-cleansing tonic.
How it is classified
- Herbal actions
- Nutritive, Alterative. Energy: neutral.
How people take it
Eaten as seaweed or taken as a capsule or powder. Iodine content differs from one product to the next, and no safe dose for thyroid use has been tested.
Tea, capsule, powder and food.
Where to get it
Grows on rocky shores of the North Atlantic and North Pacific. Sold dried as powder, capsules and tea, and as a weight-loss supplement. Iodine levels swing a lot from batch to batch.
Be careful
Too much iodine can cause an overactive or underactive thyroid. Seaweed from polluted water can carry arsenic, cadmium and mercury, which can harm the kidneys. Animal studies suggest it may change how the body handles some drugs.
Avoid if: thyroid disease; pregnancy; breastfeeding; kidney disease.
Mixing with other things
- Don't mixThyroid medicine (levothyroxine (Synthroid))
Iodine can upset thyroid hormone balance and interfere with thyroid medicine.
- Use cautionHeart rhythm medicine (digoxin, amiodarone)
An animal study found it lowered absorption of amiodarone, a heart rhythm drug.
Adds up with others that carry iodine: , , , , , .
Found in these formulas
Sea moss trio (Dr. Sebi)
The honest take
Bladderwrack is a real source of iodine, so it can change thyroid levels. Its use for weight loss has no good support. The human research is tiny and mostly old, so its benefits are unproven.