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Seaweed, kelp, bladderwrack (Fucus vesiculosus)
While some complementary and alternative techniques have been studied scientifically, high-quality data regarding safety, effectiveness, and mechanism of action are limited or controversial for most therapies. Whenever possible, it is recommended that practitioners be licensed by a recognized professional organization that adheres to clearly published standards. In addition, before starting a new technique or engaging a practitioner, it is recommended that patients speak with their primary healthcare provider(s). Potential benefits, risks (including financial costs), and alternatives should be carefully considered. The below monograph is designed to provide historical background and an overview of clinically-oriented research, and neither advocates for or against the use of a particular therapy.

Related Terms

  • Acinetosporaceae (family), Acrochaetiaceae (family), agar, Akkesiphycaceae (family), alanine, Alariaceae (family), algas marinas (Spanish), algin, alginates, alginic acid, Aquamin®, arginine, Arthrocladiaceae (family), Ascophyllum nodosum, Ascoseriaceae (family), Asparagopsis armata (Harv.), aspartic acid, astaxanthin, beta-carotene, beta-glucans, Bifurcariopsidaceae (family), black-tang, bladder, bladder fucus, bladderwrack, Blasen-tang (German), Bonnemasoniaceae (family), brown algae, brown seaweed, brown seaweed extract, brown tropical seaweed, calcium, carrageenans, Carraguard®, Caulacanthaceae (family), Caulerpa lentillifera, Caulerpaceae (family), Cermiaceae (family), Champiaceae (family), chlorophyta, Chordaceae (family), Chordariaceae (family), Chordariopsidaceae (family), Choristocarpaceae (family), cobalamin, Codiaceae (family), Colaconemataceae (family), common seawrack, Corallinaceae (family), Costariaceae (family), Cruoriaceae (family), cut weed, Cutleriaceae (family), Cystocloniaceae (family), Cystophyllum fusiforme, Cystoseiraceae (family), Dasyaceae (family), Delesseriaceae (family), Delisea pulchra (Greville) Montagne, Desmarestiaceae (family), Dictyotaceae (family), dried nori, Dumontiaceae (family), Durvilleaeceae, Dyers fucus, (E)-9-oxooctadec-10-enoic acid (S6C), (E)-10-oxooctadec-8-enoic acid (S5C), Ecklonia cava, Ecklonia cava Kjellman, Ecklonia kurome, Ecklonia stolinifera, Ectocarpaceae (family), edible seaweed, Eisenia arborea, Eisenia bicyclis, Eucheuma cottonii, fatty acids, fermented tangle weed, fiber, Fucaceae (family), fucaxanthin, fuco negro (Spanish), fucoidans, fucophorethols, fucose, fucoxanthin, Fucus, Fucus distichus, Fucus evanescens, Fucus Plus®, Fucus vesiculosus, furanones, Furcellariaceae (family), galactose, Galaxauraceae (family), Gelidiaceae (family), GFS, Gigartinaceae (family), glucose, gluatmic acid, Gracilaria verrucosa, Gracilariaceae (family), green algae, green seaweed, glycine, Hai-ts'ao, Halymeniaceae (family), Heterochordariaceae (family), heterofucans, Himanthaliaceae (family), Hormosiraceae (family), iodine, iron, Ishigeaceae (family), Japanese kelp, Kappaphycus alvarezii, kelp, kelpware, knotted wrack, kombu, Laminaria cloustoni, Laminaria digitata, Laminaria japonica, Laminaria longicruris, Laminaria saccharina, Laminariaceae (family), lectins, Lessoniaceae (family), Liagoraceae (family), Lomentariaceae (family), Macrocystis pyrifera, magnesium, marine algae, marine brown algae, marine carotenoids, marine green algae, marine macroalgae, marine red algae, mekabu fucoidan, Meereiche (German), minerals, mucopolysaccharides, Nemastomataceae (family), Neoralfsiaceae (family), nori, ogonori, omega-3 fatty acids, omega-6 fatty acids, Padina gymnospora, Palmaria palmata, Palmariaceae (family), Petalonia bingamiae, Peyssonneliaceae (family), Phaeophyceae, phaeophyta, phenolics, phloroglucinol, phlorotannins, phosphonyl glycosyl ester diglycerides, phosphorus, Phyllophoraceae (family), Plocamiaceae (family), polyphenols, polysaccharides, popping wrack, Porphyra yezoensis, potassium, proline, protein, Pseudochordaceae (family), Pylaiellaceae (family), Quercus marina, Ralfsiaceae (family), raw nori, red alga, red algae, red fucus, red marine seaweed, red seaweed, Rhodomelaceae (family), Rhodophysemataceae (family), rhodophyta, Rhodymeniaceae (family), rockrack, rockweed, Sarcomeniaceae (family), Sargassaceae (family), Sargassum polycystum, Schweintang (German), Scytosiphonaceae (family), Scytothamnaceae (family), sea alga, sea algae, sea cabbage, sea kelp, sea lettuce, sea oak, sea wrack, seaware, seaweed, seaweed extract, seaweed soup, seeds of tangles, Seetang (German), sodium alginate, Solieriaceae (family), Spatoglossum schröederi, Sphacelariaceae (family), Sphaerococcaceae (family), Splachnidiaceae (family), Sporochnacaeae, Stylonemataceae (family), Stypocaulaceae (family), sulfate, sulfated polysaccharides, sulfonyl ester diglycerides, sulfuryl ester diglycerides, swine tang, tang, tangle weed, tannins, Tasmanian tororokombu, trace metals, tropical marine algae, Ulva lactuca, ulvans, Undaria pinnatifida, uronic acids, varech vésiculeux (French), ventol, vitamin B1, vitamin B2, vitamin B12, vitamin C, vitamin E, vraic, wakaame, wrack, xylose.
  • Select combination products: Xanthigen®-600 (300 milligrams of brown seaweed extract containing 2.4 milligrams of fucoxanthin and 300 milligrams of pomegranate seed oil).
  • Note: Overall, there is some disagreement over what is thought to be a seaweed over other types of algae. This bottom line focuses on the most common types of seaweed and does not include blue-green algae (Cyanobacteria), agar, or discussion of laminaria tents.


  • Seaweeds are brown or green algae that live on or near the sea floor. Fucusvesiculosus, also called bladderwrack, is a brown seaweed that belongs to the Fucaceae family. The name sometimes refers to Ascophyllum nodosum, another brown seaweed. These species often make up kelp mixtures, along with other types of seaweed.
  • Bladderwrack has been used to treat thyroid gland problems and has been used in weight loss formulas. Some studies have shown that bladderwrack may thin the blood and lower blood sugar levels.
  • Information on the active ingredients of bladderwrack is lacking. Most of the effects of bladderwrack are shared by brown seaweed species as a whole. Overall, there is not enough evidence on the safety and effectiveness of seaweed in humans.


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The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

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The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

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Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.

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Author Information

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Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to Selected references are listed below.

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The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.