Bladderwrack (Fucus vesiculosis)


Goiter and thyroid disease (including hypo- and hyperthyroid states), obesity, and cancer.

Mechanism of Action

Fucus has a high halide mineral content, including iodine, which has good bioavailability,1 and selenium, which is of central importance in regulation of the thyroid gland.2 The presence of iodine and specific selenoproteins implicated in thyroid hormone metabolism within the colloid of the thyroid gland may stimulate the gland to produce thyroxine,3 body metabolism, and promote weight loss.4

Fucoidan, a sulfated polysaccharide found in Fucus, has demonstrated anticancer activities in vivo through the modulation of host immune systems and inhibition of tumor angiogenesis.5

Fucus inhibits collagenase and elastase, enzymes that metabolically breakdown collagen and elastin, thereby explaining the plant’s traditional use in cosmetic facials and body wraps.6 This action may help protect thyroid cells from inflammatory damage.

Fucus decreases trans-sialidase activity in the blood, an enzyme associated with cholesterol accumulation.7 This may benefit patients with low thyroid function because slow metabolism is associated with excessive lipid and glucose accumulation.

Evidence-Based Research

  • Fucus may support thyroid function and improve collagen abnormalities related to poor thyroid function. Thyroid hormones direct connective matrix activities in the thyroid itself and in many other organs. Collagen breakdown is associated with immunoreactivity in the thyroid,8 based on animal studies.
  • Fucus may inhibit thyroid cancer and tumor cell invasion based on human cell culture investigations.9
  • Hypothyroidism may allow excessive deposition of collagen in the heart10 and glycosaminoglycan accumulation of pretibial myxedema and exophthalmia of Graves’ disease,11 thereby supporting that thyroid hormones may reduce collagen deposition involved in progressive fibrotic changes of diabetic nephropathy.12

Safety in Pregnancy and Breastfeeding

There is no research attesting to the safety of Fucus during pregnancy. However, traditional use as a food would suggest that as long as the consumption is not so great as to consume a toxic level of iodine, consumption of various seaweeds, including Fucus, is generally considered safe. One human investigation of iodine content of breast milk in Korean women consuming an average of 2.7 mg of iodine per day reported that the colostrum contained 2.2 mg/L and mature milk 0.9 mg/L.13

General Safety

No safety data are available, but based on the use of the Fucus as a traditional food, moderate consumption of seaweeds is generally considered safe. Seaweeds are subject to contamination with chemicals from the water in which it is harvested; therefore, the source is of concern. There have been case reports of nephrotoxicity from Fucus, possibly due to arsenic contamination.14

Iodine may support thyroid function when consumed in appropriate amounts, but it may suppress thyroid function when consumed daily and in very large amounts. In Japan, where seaweed is a dietary staple, the daily average intake of iodine has been estimated to be from 1.2 mg/day15 to as high as 3 mg/day.16 Some species of kelp provide as much as 6 mg of iodine per gram,17 and the U.S. Department of Agriculture phytochemical database estimates Fucus species to contain 5.4 mg/g of iodine.18 One study found that doses as high as 6 mg/day benefited women with cyclic mastalgia without notable toxicity, thyroid suppression, or side effects.19


There is no officially approved or standardized dosage; however this herb is generally considered safe, even at doses up to 4–6 g/day of crude dried seaweed, which would deliver roughly 400–500 µg of iodine.

Traditional Uses

Fucus is a brown seaweed species that has been traditionally used as a food. It is burned to ashes used for their salty flavor and used as a medicine topically for skin; in body wraps to support weight loss; and orally for cancer, inflammation, goiter, and thyroid disease. The term “kelp” is also used to refer to this seaweed.


1 Cell Mol Biol. 2002;48(5):563–9. Bioavailability of seaweed iodine in human beings. Aquaron R, Delange F, Marchal P, et al.

2 J Sci Food Agric. 2014;94(15):3281–90. Characterization of protein, lipid and mineral contents in common Norwegian seaweeds and evaluation of their potential as food and feed. Maehre HK, Malde MK, Eilertsen KE, et al.

3 Eur. J. Biochem. 51(2):329–36. Free diiodotyrosine effects on protein iodination and thyroid hormone synthesis catalyzed by thyroid peroxidase. Dème D, Fimiani E, Pommier J, et al.

4 Fitoterapia. 2000;71 Suppl 1:S73–82. Obesity and medicinal plants. Moro CO, Basile G.

5 Am J Hematol. 2005;78(1):7–14. Fucoidan induces apoptosis of human HS-sultan cells accompanied by activation of caspase-3 and down-regulation of ERK pathways. Aisa Y, Miyakawa Y, Nakazato T, et al.

6 BMC Complement Altern Med. 2009;9:27. Anti-collagenase, anti-elastase and anti-oxidant activities of extracts from 21 plants. Thring TS, Hili P, Naughton DP.

7 Bull Exp Biol Med. 2007;143(1):46–50. Effect of plant extracts on trans-sialidase activity in human blood plasma. Aksenov DV, Kaplun VV, Tertov VV, et al.

8 J Immunol. 2002;169(11):6530–8. Inhibition of TGFbeta1 by anti-TGFbeta1 antibody or lisinopril reduces thyroid fibrosis in granulomatous experimental autoimmune thyroiditis. Chen K, Wei Y, Sharp GC, et al.

9 Mol Cancer Res. 2011;9(6):673–87. Relaxin enhances the collagenolytic activity and in vitro invasiveness by upregulating matrix metalloproteinases in human thyroid carcinoma cells. Bialek J, Kunanuvat U, Hombach-Klonisch S, et al.

10 J Physiol Pharmacol. 2009;60(3):57–62. Experimental hypothyroidism increases content of collagen and glycosaminoglycans in the heart. Drobnik J, Ciosek J, Slotwinska D, et al.

11 Eur J Endocrinol. 2002;146(1):35–8. Evidence for thyrotropin receptor immunoreactivity in pretibial connective tissue from patients with thyroid-associated dermopathy. Daumerie C, Ludgate M, Costagliola S, et al.

12 J Endocrinol. 2011;209(2):185–91. Thyroid hormone ameliorates diabetic nephropathy in a mouse model of type II diabetes. Lin Y, Sun Z.

13 Int J Food Sci Nutr. 1999;50(3):165–71. Iodine content of human milk and dietary iodine intake of Korean lactating mothers. Moon S, Kim J.

14 Nephrology. 2003;1(2). Renal dysfunction associated with herbal remedies and dietary supplements. Garbardi S, Cormeir C, Cina J, et al.

15 Thyroid. 2008;18(6):667–8.The average of dietary iodine intake due to the ingestion of seaweeds is 1.2 mg/day in Japan. Nagataki S.

16 Thyroid Res. 2011;4:14. doi: 10.1186/1756-6614-4-14. Assessment of Japanese iodine intake based on seaweed consumption in Japan: A literature-based analysis. Zava TT, Zava DT.

17 Thyroid. 2004;14(10):836–41. Variability of iodine content in common commercially available edible seaweeds. Teas J, Pino S, Critchley A, et al.


19 Breast J. 2004;10(4):328–36. The effects of supraphysiologic iodine on patients with cyclic mastalgia. Kessler JH.