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bladderwrack (generic name)

treats Goiter, Antibacterial/antifungal, Anticoagulant, Weight loss, Antioxidant, Cancer, and Diabetes
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Average Ratings


Adults (18 years and older)

Soft capsules (alcohol extract) in doses of 200 to 600 milligrams daily have been taken by mouth. Tablets have also been used, initially taken three times per day and gradually increased to 24 tablets per day. 16 grams of bruised plant mixed with one pint of water has been used, administered in 2 fluid ounce doses three times per day or an alcoholic liquid extract in a dose of 4 to 8 milliliters before meals.

Topical (on the skin) bladderwrack and seaweed patches are sold commercially as weight loss products, although there is a lack of commonly accepted or well tested doses.

Children (under 18 years old)

There is not enough scientific evidence to recommend the safe use of bladderwrack in children. Because of the iodine content and potential for contamination with heavy metals, it may be inadvisable for use in children.


DISCLAIMER: Many complementary techniques are practiced by healthcare professionals with formal training, in accordance with the standards of national organizations. However, this is not universally the case, and adverse effects are possible. Due to limited research, in some cases only limited safety information is available.


Avoid in individuals with an allergy/hypersensitivity to Fucus vesiculosus, any of its components, or iodine, as sensitivity may occur.

Side Effects and Warnings

Most adverse effects appear related to the high iodine content, heavy metal, or other contamination of bladderwrack preparations, rather than to the seaweed itself. Because of the potential contamination of bladderwrack with heavy metals, its consumption should always be considered potentially unsafe.

Based on the known effects of iodine toxicity and case reports, the high iodine content in bladderwrack may lead to abnormal thyroid conditions. In theory, bladderwrack may increase or decrease blood thyroid hormone levels. In addition, acne-type skin lesions may occur, and there are reports of severe acne exacerbations with the use of kelp. Iodine may also cause a brassy taste, increased salivation, and stomach irritation.

Reports of kidney and nerve toxicity have occurred in persons taking seaweed/kelp, attributed to high levels of arsenic. Abnormal bleeding and reduced blood platelet count was attributed to contaminants in a kelp product. Bladderwrack may contain vitamins and minerals, calcium, magnesium, potassium, and sodium and may increase blood levels.

Extracts of bladderwrack may cause lowered blood sugar. Caution is advised in patients with diabetes or hypoglycemia and in those taking drugs, herbs, or supplements that affect blood sugar. Serum glucose levels may need to be monitored by a healthcare provider, and medication adjustments may be necessary.

Bladderwrack may have blood-thinning (anticoagulant) properties. Abnormal bleeding, petechiae, and autoimmune thrombocytopenic purpura with dyserythropoiesis have been reported. Caution is advised in patients with bleeding disorders or taking drugs that may increase the risk of bleeding. Dosing adjustments may be necessary.

Laxative properties have traditionally been attributed to chronic use of bladderwrack and other brown seaweeds and may be due to the component alginic acid, present in many laxative agents.

Pregnancy and Breastfeeding

Bladderwrack is not recommended during pregnancy or lactation due to a lack of reliable scientific information and because of the presence of high levels of iodine and possible heavy metal contamination.

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