Bladderwrack
Fucus vesiculosus · Fucaceae
Reviewed by The Sarv Health Team · Updated July 6, 2026 · Our editorial process
Bladderwrack is a common brown seaweed of cold Atlantic and Pacific shores, recognizable by the paired air bladders that keep its fronds afloat. It holds an important place in coastal herbal medicine as one of the richest natural sources of iodine, the mineral the thyroid gland requires to make its hormones. For this reason bladderwrack is traditionally used to support healthy thyroid function and metabolism, and it was one of the original remedies for an underactive thyroid and goiter caused by iodine deficiency. Rich in minerals, it is a nourishing tonic that also supplies its slimy soluble fibers, alginates and fucoidans, which soothe the digestive tract, support gut health, and are studied for anti-inflammatory and immune benefits. Applied to the skin and in seaweed baths it is used to soothe and nourish. Salty, cooling, and mineral-rich, bladderwrack is treasured as a remedy for the thyroid, metabolism, and mineral nourishment.
Medicinal Uses
Bladderwrack is a brown seaweed that grows abundantly on rocky coastlines, and it was one of the first sources from which iodine was isolated. Long used as food and medicine in coastal cultures, it is valued as salty, cooling, and deeply mineral-rich. Its key constituents include iodine and other trace minerals, the polysaccharides alginic acid (alginates) and fucoidan, the pigment fucoxanthin, and various vitamins.
The foremost medicinal use of bladderwrack relates to the thyroid gland. Because it is one of the richest natural sources of iodine, the essential building block of thyroid hormones, it is traditionally used to support healthy thyroid function and a healthy metabolic rate, and it was historically the classic remedy for an underactive thyroid and for goiter caused by iodine deficiency. On account of this potent iodine content it should be used with care and avoided in those with certain thyroid conditions or on thyroid medication without professional advice.
Bladderwrack is also a broadly nourishing mineral tonic, supplying iodine, potassium, magnesium, calcium, iron, and other trace elements that support overall vitality, healthy skin, hair, and bones, and general nourishment.
Its abundant soluble fibers, especially alginates and fucoidan, form a soothing gel that supports the digestive tract, can ease heartburn and irritation, promote healthy digestion and elimination, and act as a prebiotic for the gut. Fucoidan in particular is studied for anti-inflammatory, immune-supporting, and other protective effects.
Bladderwrack is also applied externally in seaweed wraps and baths to soften, soothe, and nourish the skin. Salty, cooling, and mineral-rich, it is treasured as a remedy for the thyroid, metabolism, and deep mineral nourishment.
Benefits
Supports healthy thyroid function, provides a rich natural source of iodine, supports a healthy metabolism, supplies abundant minerals, nourishes skin, hair, and bones, soothes the digestive tract, supports gut and prebiotic health, may ease heartburn and irritation, provides fucoidan with anti-inflammatory and immune benefits, nourishes the skin externally
How to Use & Dosage
Because of its high iodine content, use in moderation and consult a practitioner if you have a thyroid condition or take thyroid medication.
1/2 to 1 teaspoon per day, sprinkled in food or drinks.
500-1000 mg per day, divided into doses.
Steep 1 teaspoon of dried bladderwrack in hot water for 10-15 minutes. Drink up to 1 cup daily.
More Info
Frequently asked questions
What is Bladderwrack used for?
Bladderwrack is a brown seaweed that grows abundantly on rocky coastlines, and it was one of the first sources from which iodine was isolated. Long used as food and medicine in coastal cultures, it is valued as salty, cooling, and deeply mineral-rich. Its key constituents include iodine and other trace minerals, the polysaccharides alginic acid (alginates) and fucoidan, the pigment fucoxanthin, and various vitamins.
What are the benefits of Bladderwrack?
Supports healthy thyroid function, provides a rich natural source of iodine, supports a healthy metabolism, supplies abundant minerals, nourishes skin, hair, and bones, soothes the digestive tract, supports gut and prebiotic health, may ease heartburn and irritation, provides fucoidan with anti-inflammatory and immune benefits, nourishes the skin externally
How do you take Bladderwrack?
Common preparations include note, powder, capsules, infusion. See the dosage guidance above, and consult a qualified practitioner for amounts suited to you.
This information is for general wellness and educational purposes only and is not medical advice. Consult a qualified healthcare provider before using any herb — especially if you are pregnant, nursing, or taking medication.
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