About Herbs

Bottom Line: The claims of beneficial effects of bladder wrack have not been confirmed in clinical trials.

Bladder wrack extract is rich in iodine and is claimed to stimulate thyroid activity to treat obesity. There is no evidence to support this. Women who took bladder wrack showed improvement in their menstrual symptoms. Topical application of a bladder wrack extract showed benefits for skin. Further studies are needed to confirm these effects.

Bladder wrack has not been studied in large scale clinical trials.

Patients with thyroid disorder or hormonal-sensitive cancers should talk to their doctors before using bladder wrack.  

This product is regulated by the FDA as a dietary supplement. Unlike approved drugs, supplements are not required to be manufactured under specific standardized conditions. This product may not contain the labeled amount or may be contaminated. In addition, it may not have been tested for safety or effectiveness.

Bladder wrack is often referred to as brown kelp but it should not be confused with "kelp," another species of seaweed.

Maine sea coast vegetables

Bladder wrack is a seaweed prevalent on the Atlantic and Pacific coasts from Europe to Asia. It is often referred to as brown kelp but it should not be confused with "kelp," another species of seaweed. Bladder wrack is consumed as food and medicine and is a rich source of iodine. It is used in traditional medicine to treat hypothyroidism due to iodine deficiency and has been proposed as a weight loss supplement. No clinical studies have verified this effect. Bladder wrack and related seaweed species demonstrate anti-estrogenic effects. It is believed responsible for the reduced risk of estrogen-related cancers in Asian populations ⁽¹⁾ and may improve menstrual symptoms ⁽¹⁾. Further studies are needed to clarify such effects.
Bladder wrack extract also demonstrated anti-collagenase and antioxidant properties ⁽⁶⁾; topical application of bladder wrack extract may help improve skin ⁽²⁾.
Bladder wrack should be used with caution in patients with hormonal-sensitive cancers.

Atlantic sea kelp, seaweed

Weight loss

Skin care

Cellulite

Hypothyroidism

Fatigue

Menstrual abnormalities

Bladder wrack extract is rich in iodine and has been used as a natural supplement for thyroid disorder and for obesity. It exhibits antiestrogenic effects. Bladder wrack has also been shown to lower plasma cholesterol levels by competitive inhibition via fucosterols. As cholesterol is a precursor for the biosynthesis of steroid hormones, a reduction in cholesterol bioavailability may lower circulating estradiol levels thereby altering menstrual cycling patterns ⁽¹⁾. An extract of bladder wrack reduced 17,beta-estradiol levels and also acted as a competitive inhibitor of estradiol binding to alpha- and beta- estrogen receptors in vitro ⁽³⁾. In rats, treatment with bladder wrack lengthened overall estrous cycles and reduced circulating 17,beta-estradiol levels ⁽⁴⁾. Bladder wrack and related seaweed species have been shown to exhibit anti-hypertensive effects via angiotensin-I-converting enzyme inhibition. The antibacterial and antioxidant properties are thought to be due to its polyphenolic contents ⁽¹⁾. Topical bladder wrack extract reduced skin thickness and improved the mechanical/elastic properties ⁽²⁾.

Consumption of Bladder wrack harvested from polluted waters may cause nephrotoxicity due to the presence of heavy metals such as arsenic, cadmium and mercury ⁽⁵⁾.

*This product is regulated by the FDA as a dietary supplement. Unlike approved drugs, supplements are not required to be manufactured under specific standardized conditions. This product may not contain the labeled amount or may be contaminated. In addition, it may not have been tested for safety or effectiveness.

Bladder wrack acts as an estrogenic receptor modulator and should be used with caution in patients with hormonal-sensitive cancers.

Theoretically, bladder wrack may have an additive effect when taken with cholesterol-lowering and antihypertensive medications ⁽¹⁾.

1. Skibola CF. The effect of Fucus vesiculosus, an edible brown seaweed, upon menstrual cycle length and hormonal status in three pre-menopausal women: a case report. BMC Complement Altern Med. 2004;4:10.
2. Fujimura T, Tsukahara K, Moriwaki S, et al. Treatment of human skin with an extract of Fucus vesiculosus changes its thickness and mechanical properties. J Cosmet Sci 2002;53(1):1-9.
3. Skibola CF, Curry JD, VandeVoort C, et al. Brown kelp modulates endocrine hormones in female sprague-dawley rats and in human luteinized granulosa cells. J Nutr 2005;135(2):296-300.
4. Moro CO, Basile G. Obesity and medicinal plants. Fitoterapia 2000;71 Suppl 1:S73-82.
5. Conz PA, La Greca G, Benedetti P, et al. Fucus vesiculosus: a nephrotoxic alga? Nephrol Dial Transplant 1998;13(2):526-7.
6. Thring TS, Hili P, Naughton DP. Anti-collagenase, anti-elastase and anti-oxidant activities of extracts from 21 plants. BMC Complement Altern Med. 2009 Aug 4;9:27.