Bladderwrack

Fucus vesiculosus, F. distichus

Also: Rockweed, Sea wrack, Fucus

CoolingMoisteningRelaxing

An iodine-rich seaweed for a thyroid short of iodine.

A rubbery olive-brown seaweed of rocky shores, its forked fronds studded with air bladders that buoy it up toward the light when the tide comes in. Bladderwrack supplies iodine and a wide range of sea minerals, nourishing an iodine-starved thyroid and a depleted body.

Energetics: Cooling, moistening, relaxing
Taste: Salty, briny
Family: Fucaceae (rockweed family)
Parts used: Fronds

Medicinal uses 3

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Traditional useLab and mechanism studiesClinical studies

Underactive thyroidTLC
Supplies the iodine an iodine-starved thyroid needs to make its hormones; the classic seaweed remedy for goiter.
Depletion & mineral needsTLC
A dense source of iodine, calcium, magnesium, potassium, and trace minerals that land plants rarely carry.
Joint pain & arthritisTLC
A hot compress of the softened fronds eases aching joints.

Preparations

Small daily amounts of powder, seaweed in food, and hot compresses and baths.

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Cautions

Too much iodine can push the thyroid either way and can flare autoimmune thyroid disease such as Hashimoto's or Graves'. Get thyroid tests first, and use it only with a practitioner's guidance if you have any thyroid condition.
Seaweeds soak up heavy metals such as arsenic and cadmium from polluted water. Buy tested seaweed from clean, cold water.
Leave it out if you react to iodine.

Medication interactions

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Pregnancy & breastfeeding

PregnancyAvoid concentrated amounts

Concentrated seaweed can deliver far too much iodine, which disturbs the baby's developing thyroid, and it can carry heavy metals. Iodized salt, dairy, and a prenatal vitamin with iodine cover pregnancy's needs.

BreastfeedingAvoid concentrated amounts

Excess iodine passes into breast milk and can upset a baby's thyroid.

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Folklore

In 1811 the French chemist Bernard Courtois, making saltpeter for Napoleon's gunpowder from seaweed ash, saw violet fumes rise from the residue and had found a new element, iodine. Nine years later the Geneva physician Jean-François Coindet began treating goiter with iodine, the active ingredient in the old remedy of burnt sponge and seaweed. On the shore, bladderwrack's canopy shelters periwinkles, crabs, and young fish when the tide runs out.

How to grow

It cannot be grown at home. Harvest only from clean water, cutting the upper fronds with scissors and leaving the holdfast on the rock so it regrows; check local harvest rules first. Dry it quickly in the sun or a low oven.

In the wild

Rocky intertidal shores of the North Atlantic and North Pacific; Fucus distichus is the common rockweed of Pacific Northwest beaches.

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