Basic Information

Common name: Bladderwrack

Other Names: Kelp, Seaweed, Black Tany, Hai-ts’ao, Cutweed, Seawrack, Bladder Fucus, Dryer’s Fucus, Red Fucus, Rockwrack

Latin Binomial: Fucus vesiculosus

Parts Used: Whole Plant (Thallus)


Medicinal Uses

Part of the brown algae group of seaweeds, Bladderwrack is useful for the treatment of goiter and underactive thyroid conditions, including Hashimoto’s thyroiditis (Kasagi,, 2003). Numerous studies have found it to be effective for weight loss (Chater, 2015), however, there is speculation that it is only effective in overweight individuals with weight gain due to hypothyroid issues. It also has anti-inflammatory activity both when taken internally and topically.


Key Constituents

  • Polyphenolic Acids (stimulate the immune system)
  • Polysaccharides (stimulate the immune system)
  • Diglycerides
  • Omega-3 Fatty Acids (Polar Lipids)
  • Iodine



  • Anti-Hypothyroid
  • Anti-Rheumatic
  • Laxative
  • Diuretic


Body Organs Acted Upon

Endocrine (thyroid)


When and How to Use It

May be taken as a pill, tincture, or infusion. As an infusion, use 2-3 teaspoons of dried herb to 1 cup of boiling water and steep for 10 minutes, three times per day. As a tincture, take 2-6 ml, three times per day. As a pill, follow recommended instructions on the package.


Safety Considerations

Increases thyroid activity due to its high iodine content, therefore, not recommended for those with normal-functioning thyroid as it is likely to cause hyperthyroidism (Clark,, 2003 and Shilo, 1986). One of its polysaccharides, fucoidan, has binding properties that decrease iron, potassium, and sodium absorption in the small intestines (Marieb, 2015).

Increased iodine intake can be harmful for the fetus, therefore, is not recommended for pregnant women, due to the high variability of amounts of iodine in different sources of bladderwrack. Inform your doctor if taking with thyroid medications and follow the doctor’s instructions on how/if to proceed with this herb.



Chater, P.I., Wilcox, M.D., Houghton, D., and Pearson, J.P. (2015). The role of seaweed bioactives in the control of digestion: implications for obesity treatments. Food Funct. 6(11). 3420-7. doi: 10.1039/c5fo00293a.

Chevallier, Andrew (2000). Encyclopedia of herbal medicine: The definitive reference to 550 herbs and remedies for common ailments, 2nd ed. Dorling Kindersley. New York, NY.

Clark, C.D., Bassett, B., and Burge, M.R. (2003). Effects of kelp supplementation on thyroid function in euthyroid subjects. Endocr Pract. 9(5). 363-9.

Hoffmann, David. (2003). Medical herbalism: The science and practice of herbal medicine. Healing Arts Press. Rochester, VT.

Kasagi, K., Iwata, M., Misaki, T., and Konishi, J. (2003). Effect of iodine restriction on thyroid function in patients with primary hypothyroidism. Thyroid. 13(6). 561-7.

Marieb, E.N. (2015). Essentials of human anatomy and physiology, 11th ed. Pearson Education, Inc. Glenview, IL.

Shilo, S. and Hirsch, H.J. (1986). Iodine-induced hyperthyroidism in a patient with a normal thyroid gland. Postgrad Med J. 62(729). 661-2.

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