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Seaweed, kelp, bladderwrack (Fucus vesiculosus)

Synonyms / Common Names / Related Terms
Algin, alginic acid, black-tang, bladder, bladder fucus, Blasen-tang, calcium, common seawrack, cut weed, Dyers fucus, Fucaceae (family), fucophorethols, Fucus, Fucus Plus®, Fucus vesiculosus, Hai-ts'ao, iodine, kelp, kelpware, knotted wrack, magnesium, Meereiche, mucopolysaccharides, phenolics, phloroglucinol, phlorotannins, phosphonyl glycosyl ester diglycerides, popping wrack, potassium, Quercus marina, red fucus, rockrack, rockweed, schweintang, sea kelp, sea oak, seetang, seaware, seaweed, sea wrack, sodium alginate, sulphonyl ester diglycerides, sulphuryl ester diglycerides, swine tang, tang, trace metals, Varech vesiculeux, vraic, wrack.

Mechanism of Action
  • Constituents: 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.
  • Antibacterial effects: A lectin-like mucopolysaccharide found in vitro to have activity against Candida guilliermondii also inhibits growth of multiple Neisseria meningitidis and Escherichia coli strains.6
  • Anticoagulant effects: Fucoidan, a high molecular weight sulfated polysaccharide isolated from Fucus vesiculosus, has been found in vitro to enhance the heparin-cofactor II-thrombin reaction through the formation of a ternary complex with both heparin-cofactor II and thrombin.1,12,2 An additional ex vivo analysis using human plasma has demonstrated the ability of fucoidan to prolong the activated partial thromboplastin time.1 Fucoidans isolated from F. vesiculosus have stronger anticoagulant properties than fucans isolated from other brown algae species, including Sargassum muticum and Laminaria digitata, due to higher contents of fucose and sulfate.7
  • Anti-estrogenic effects: Based on animal evidence, sodium alginate (soluble algae polysaccharide) may lower lipid levels in the blood.8 Because cholesterol is needed to produce sex hormones, it has been suggested that oral ingestion of kelp may affect circulating sex hormone levels and menstrual cycling patterns.3 Researchers tested the effects of bladderwrack to determine if its effects on women with or at high risk for estrogen-dependent diseases. Three pre-menopausal women with abnormal menstrual cycling patterns and/or menstrual-related disease histories received bladderwrack. Bladderwrack significantly increased menstrual cycle length by 5.5-14 days. In addition, hormone measurements in one woman revealed significant anti-estrogenic and progestagenic effects. Mean baseline 17beta-estradiol levels were reduced from 626 ± 91 to 164 ± 30pg/mL (p=0.04) following 700mg daily, which decreased further to 92.5.0 ± 3.5pg/mL (p=0.03) with the 1.4g daily dose. Mean baseline progesterone levels increased from 0.58 ± 0.14 to 8.4 ± 2.6ng/mL with the 700mg daily dose (p=0.1), which increased further to 16.8 ± 0.7ng/mL with the 1.4g daily dose (p=0.002). The authors concluded that dietary bladderwrack may prolong the menstrual cycle and exert anti-estrogenic effects in pre-menopausal women. The authors also suggested that seaweed may help reduce the risk of estrogen-related cancers observed in Japanese populations. However, these preliminary findings need to be confirmed in well-controlled clinical trials.
  • Antifungal effects: A lectin-like mucopolysaccharide isolated from F. vesiculosus has been found to be specific for complex carbohydrates. This mucopolysaccharide causes agglutination of the yeast Candida guilliermondii, and inhibits the growth of C. guilliermondii by 99.2%.13 In vivo studies are lacking.
  • Antilipemic effects: Sodium alginate, a soluble algae polysaccharide from the cell walls of brown algae, can lower lipid levels in animals without altering weight or growth when added to a cholesterol and cholate diet.8
  • Antineoplastic effects: Yamamoto et al. found the extract of Sargassum fulvellum to possess antitumor activity against human sarcoma-180 ascitic cells both in vitro and in mice and attributed these effects to a sulfated polysaccharide.9 These components have since been isolated from Ascophyllum nodosum and Fucus vesiculosus, as well as from other brown seaweed species. A fucan isolated from Ascophyllum nodosum was shown to also suppress human sarcoma-180 ascitic cells both in vitro and in mice.10,11 The mechanism of this antineoplastic effect is currently unknown. These fucans were also found to suppress growth of non-small-cell human bronchopulmonary carcinoma (NSCLC-N6) cells in vitro and in vivo.11 Furthermore, a low molecular weight fucan isolated from the brown seaweed Ascophyllum nodosum seems to suppress the growth of CCL39 fibroblasts and COLO320DM human colon adenocarcinoma cells in vitro.10
  • Antioxidant effects: In vitro analysis has demonstrated that Fucus vesiculosus inhibits oxidation of methyl linoleate with a shortened induction period similar to results seen with vitamin E, but without the oxygen uptake suppression at t0.7
  • Laxative effects: Laxative properties of bladderwrack and other brown seaweeds (Phaeophyceae) have traditionally been attributed to the component alginic acid, a hydrophilic colloidal polysaccharide.
  • Thyroid activity: Kelp or bladderwrack products are frequently high in iodine content, and have been used traditionally for thyroid diseases. In humans, there are case reports of transient hyperthyroidism as a result of bladderwrack ingestion.4,5 Bladderwrack products contain up to 600mcg per gram of iodine, while normal human iodine intake is approximately 100-200mcg/day. Individuals ingesting bladderwrack or kelp products as food or supplements may ingest up to 30 times this amount. Chronic iodine toxicity may result in hypothyroidism, hyperthyroidism, goiter, or myxedema, although many individuals remain euthyroid. Systematic study of the effects of bladderwrack in humans is currently lacking, and there may be other active constituents. In terms of iodine content, a widely accepted standardization of iodine content in bladderwrack is lacking at this time, although some products may list iodine content on the label.
  • Weight loss effects: Theoretically, the thyroid stimulatory properties of bladderwrack may cause hypermetabolic weight loss. However, its anorectic properties have not been adequately evaluated in humans.

  • A mucopolysaccharide isolated from Fucus vesiculosus inhibited the growth of many Neisseria meningitidis strains at a concentration of 5mcg/mL and was bactericidal at concentrations above 10mcg/mL.6 The growth of select Escherichia coli strains was also inhibited by this mucopolysaccharide at concentrations over 10mcg/mL.

  1. Church FC, Meade JB, Treanor RE, and et al. Antithrombin activity of fucoidan. The interaction of fucoidan with heparin cofactor II, antithrombin III, and thrombin. J Biol Chem 2-25-1989;264(6):3618-3623. 2914965
  2. Durig, J., Bruhn, T., Zurborn, K. H., Gutensohn, K., Bruhn, H. D., and Beress, L. Anticoagulant fucoidan fractions from Fucus vesiculosus induce platelet activation in vitro. Thromb Res 3-15-1997;85(6):479-491. 9101640
  3. Skibola, C. F. 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 8-4-2004;4:10. 15294021
  4. Eliason, B. C. Transient hyperthyroidism in a patient taking dietary supplements containing kelp. J Am Board Fam.Pract 1998;11(6):478-480. 9876004
  5. Shilo, S. and Hirsch, H. J. Iodine-induced hyperthyroidism in a patient with a normal thyroid gland. Postgrad Med J 1986;62(729):661-662. 3748931
  6. Criado MT and Ferreiros CM. Toxicity of an algal mucopolysaccharide for Escherichia coli and Neisseria meningitidis strains. Rev Esp Fisiol 1984;40(2):227-230. 6237397
  7. Grauffel V, Kloareg B, Mabeau S, and et al. New natural polysaccharides with potent antithrombic activity: fucans from brown algae. Biomaterials 1989;10(6):363-368. 2804225
  8. Wang, C. and Yang, G. [Comparison of effects of two kinds of soluble algae polysaccharide on blood lipid, liver lipid, platelet aggregation and growth in rats]. Zhonghua Yu Fang Yi Xue Za Zhi 1997;31(6):342-345. 9863067
  9. Yamamoto I, Nagumo T, Fujihara M, and et al. Antitumor effect of seaweeds. II. Fractionation and partial characterization of the polysaccharide with antitumor activity from Sargassum fulvellum. Jpn J Exp Med 1977;47(3):133-140. 916293
  10. Ellouali M, Boisson-Vidal C, Durand P, and et al. Antitumor activity of low molecular weight fucans extracted from brown seaweed Ascophyllum nodosum. Anticancer Res 1993;13(6A):2011-2020. 8297108
  11. Riou D, Colliec-Jouault S, Pinczon du Sel D, and et al. Antitumor and antiproliferative effects of a fucan extracted from ascophyllum nodosum against a non-small-cell bronchopulmonary carcinoma line. Anticancer Res 1996;16(3A):1213-1218. 8702239
  12. Colliec S, Fischer AM, Tapon-Bretaudiere J, and et al. Anticoagulant properties of a fucoidan fraction. Thromb Res 10-15-1991;64(2):143-154. 1811335
  13. Criado, M. T. and Ferreiros, C. M. Selective interaction of a Fucus vesiculosus lectin-like mucopolysaccharide with several Candida species. Ann Microbiol (Paris) 1983;134A(2):149-154. 6223551

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