Fucus vesiculosus

Black Tang, Rockweed, Bladder Fucus, Sea Oak, Black Tany, Cut Weed, Dyers Fucus, Red Fucus, Rock Wrack.

Traditional Use

Bladderwrack thrives in many of the world’s seas and oceans. Historically, people who lived close to the sea had low rates of thyroid problems due to their ingestion of iodine rich foods. These included seaweeds, and in fact Bladderwrack is one of the highest iodine containing sea vegetables known.
It was recognised in the early 1800’s for its high iodine content and as such became widely used as a treatment for goitre (swelling of the neck due to enlarged thyroid glands). By the 1860’s, Bladderwrack was also being used to counteract obesity by speeding up metabolism.


Pacific and Atlantic Oceans, North Sea, Baltic Sea and Western Mediterranean

Parts used

Whole Seaweed


Bladderwrack contains iodine, calcium, magnesium, potassium, sodium, minerals, trace metals, phenolics, phloroglucinol, fucophorethols, phlorotannins, mucopolysaccharides, algin, lipids, and sulphuryl-, sulphonyl- and phosphonyl-glycosyl ester diglycerides.


People with an iodine allergy should not use Bladderwrack. If you are taking any prescription medications, especially in the case of thyroid disorders, please consult your healthcare professional before consuming Bladderwrack.


Thyroid Health
The thyroid gland is an absolutely vital part of the body located at the front of the neck. It secretes hormones which stimulate the metabolic system, breathing, body temperature and heart rate. An overactive thyroid can lead to feelings of fatigue and abnormal weight loss. Conversely, an underactive thyroid can lead to feelings of sluggishness and an inability to lose weight, regardless of diet.
One of the most critical nutrients for the thyroid is iodine – a compound that is sadly lacking in many Western diets. The thyroid gland contains the highest concentration of iodine than any other organ in the body and you cannot make thyroid hormones without sufficient levels of iodine. Bladderwrack is naturally high in this important nutrient, and in fact Bladderwrack was used to distil the first examples of iodine in the 19th century. According to Dr David Brownstein, author of the bestselling book, “Iodine: Why You Need It, Why You Can’t Live Without It”, iodine levels have been declining over the last 30-40 years whilst thyroid disorders have been increasing. He found that over 95% of his patients with thyroid disorders were iodine deficient.
Whilst it is best to work with a health practitioner who is knowledgeable about iodine therapy if a thyroid disorder is present, keeping your iodine levels up will go a long way to ensure a healthy thyroid remains that way.

Healthy Weight Loss
The iodine found in Bladderwrack is in highly bioavailable form because of the way it interacts with the thyroid stimulating hormone (TSH). Iodine is known to stimulate metabolism which in turn leads to weight loss. A sluggish thyroid has long been known to contribute to weight gain and metabolic syndrome. Bladderwrack is also a rich source of fucoxanthin, a carotenoid that is currently being studied for its potential fat-burning effects.
This seaweed is also a natural diuretic, flushing unwanted fluid from the body to combat bloating and water retention. Bladderwrack also makes an appearance in many anti-cellulite creams – cellulite is caused by fluid trapped between fat cells beneath the skin. Its diuretic qualities help to rid the body of the fluid build-up that produces cellulite.
Eye Health
Bladderwrack is not only rich in beta-carotene (plant-based vitamin A), it contains the nutrients fucoxanthin and fucoidan which Chinese scientists are heralding as the “eye nutrients of the future”. Fucoxanthin is the primary part of the light-absorbing mechanism of the seaweed and is what gives it a brown or olive-green colour. It is known that the blue light emitted from many types of computer, mobile and hand-held devices is damaging to vision. As a type of carotenoid known as a xanthophyll, fucoxanthin absorbs blue-green to yellow-green colours of visible light which helps protect vision.
Whilst studies are still preliminary, researchers found that fucoidan may be effective against age-related macular degeneration because it reduces extraneous blood vessel growth where cells have not been receiving enough oxygen. Like fucoxanthin, fucoidan has been found to help resist premature cell aging and death.


With a long history of traditional use, Bladderwrack was mentioned by the Greek physician Dioscorides in his “De Materia Medica”, where he recommended it for “gouty afflictions” and inflammation.

The Romans used this seaweed to soothe joint pains and as a treatment for tuberculosis. 

In magical folklore, Bladderwrack is a herb of protection – especially for those sailing across the ocean. It was also used to increase psychic powers and for protection against mental derangement. 

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