Seaweed, kelp, bladderwrack (Fucus vesiculosus)
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| Seaweed, kelp, bladderwrack |
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Fucus vesiculosus is a brown seaweed that grows on the northern coasts of the Atlantic and Pacific oceans and the North and Baltic seas. Its name is sometimes used for Ascophyllum nodosum , which is another brown seaweed that grows alongside Fucus vesiculosus . These species are often included in kelp preparations along with other types of seaweed.
- The Vietnamese, as well as other Asian populations, consume seaweed as food in various forms: raw in a salad and as a vegetable, pickled with sauce or with vinegar, as a relish or in sweetened jellies, and also cooked for vegetable soup. As an herbal medicine, seaweed has been used for traditional cosmetics, treatments for cough, asthma, hemorrhoid, boils, goiters, stomach ailments, and urinary diseases, and for reducing the incidence of tumors, ulcers, and headaches. Vietnam has an abundance of algae floral with a total number of species estimated to be nearly 1,000 of which there are 638 species of marine algae identified.
- Black-tang, bladder, bladder fucus, bladderwrack, Blasen-tang, brown algae, common seawrack, cut weed, Dyers fucus, edible seaweed, fucoidan, fucoxantin, Fucus, green algae, Hai-ts'ao, kelp, kelpware, knotted wrack, Meereiche, Quercus marina, popping wrack, red algae, red fucus, rockrack, rockweed, schweintang, sea kelp, sea oak, seetang, seaware, seaweed, sea wrack, swine tang, tang, Varech vesiculeux, vraic, wrack.
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
| Uses based on scientific evidence | Grade* |
| Antibacterial/antifungal
Laboratory study suggests antifungal and antibacterial activity of bladderwrack. However, there are no reliable human studies to support use as an antibacterial or antifungal agent.
| C |
| Anticoagulant (blood-thinner)
Laboratory study has found anticoagulant properties in fucans or fucoidans, which are components of brown algae such as bladderwrack. However, there are no high quality human studies available to support this use.
| C |
| Antioxidant
Laboratory study suggests antioxidant activity in fucoidans, which are components in some brown algae. However, there is a lack of high quality human studies available to support use as an antioxidant.
| C |
| Cancer
Several brown algae, including bladderwrack ( Fucus vesiculosus ), appear to suppress the growth of various cancer cells in animal and laboratory studies. However, currently there is a lack of reliable human studies available to support a recommendation for use in cancer.
| C |
| Diabetes
Based on animal research, extracts of bladderwrack may lower blood sugar levels. However, there is a lack of reliable human studies available to support a recommendation for use in diabetes.
| C |
| Goiter (thyroid disease)
Bladderwrack contains variable levels of iodine. As a result, it has been used to treat thyroid disorders, such as goiters. While the evidence does suggest thyroid activity, there is not enough research to support this use of bladderwrack.
| C |
| Weight loss
Bladderwrack and other seaweed products are often marketed for weight-loss. However, safety and effectiveness have not been studied in humans.
| C |
*Key to grades
A: Strong scientific evidence for this use;
B: Good scientific evidence for this use;
C: Unclear scientific evidence for this use;
D: Fair scientific evidence against this use;
F: Strong scientific evidence against this use.
Grading rationale
Uses based on tradition or theory
The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Antiviral, atherosclerosis (hardening of the arteries), arthritis, benign prostatic hypertrophy (BPH or enlarged prostate), bladder inflammatory disease, eczema, edema, enlarged glands, fatigue, hair loss, heart disease, heartburn, herpes simplex virus, high cholesterol, kidney disease, laxative, lymphoma, malnutrition, menstruation irregularities, orchitis (swollen or painful testes), parasites, psoriasis, radiation protection, rheumatism, sore throat, stool softener, stomach upset, ulcer, urinary tract tonic.
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.
Adults (18 years and older)
- Soft capsules (alcohol extract) in doses of 200 to 600 milligrams daily have been taken by mouth. Tablets have also been used, initially taken three times per day and gradually increased to 24 tablets per day. 16 grams of bruised plant mixed with one pint of water has been used, administered in 2 fluid ounce doses three times per day or an alcoholic liquid extract in a dose of 4 to 8 milliliters before meals.
- Topical (on the skin) bladderwrack and seaweed patches are sold commercially as weight loss products, although there is a lack of commonly accepted or well tested doses.
Children (under 18 years old)
- There is not enough scientific evidence to recommend the safe use of bladderwrack in children. Because of the iodine content and potential for contamination with heavy metals, it may be inadvisable for use in children.
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.
Allergies
- Avoid in individuals with an allergy/hypersensitivity to Fucus vesiculosus , any of its components, or iodine, as sensitivity may occur.
Side Effects and Warnings
- Most adverse effects appear related to the high iodine content, heavy metal, or other contamination of bladderwrack preparations, rather than to the seaweed itself. Because of the potential contamination of bladderwrack with heavy metals, its consumption should always be considered potentially unsafe.
- Based on the known effects of iodine toxicity and case reports, the high iodine content in bladderwrack may lead to abnormal thyroid conditions. In theory, bladderwrack may increase or decrease blood thyroid hormone levels. In addition, acne-type skin lesions may occur, and there are reports of severe acne exacerbations with the use of kelp. Iodine may also cause a brassy taste, increased salivation, and stomach irritation.
- Reports of kidney and nerve toxicity have occurred in persons taking seaweed/kelp, attributed to high levels of arsenic. Abnormal bleeding and reduced blood platelet count was attributed to contaminants in a kelp product. Bladderwrack may contain vitamins and minerals, calcium, magnesium, potassium, and sodium and may increase blood levels.
- Extracts of bladderwrack may cause lowered blood sugar. Caution is advised in patients with diabetes or hypoglycemia and in those taking drugs, herbs, or supplements that affect blood sugar. Serum glucose levels may need to be monitored by a healthcare provider, and medication adjustments may be necessary.
- Bladderwrack may have blood-thinning (anticoagulant) properties. Abnormal bleeding, petechiae, and autoimmune thrombocytopenic purpura with dyserythropoiesis have been reported. Caution is advised in patients with bleeding disorders or taking drugs that may increase the risk of bleeding. Dosing adjustments may be necessary.
- Laxative properties have traditionally been attributed to chronic use of bladderwrack and other brown seaweeds and may be due to the component alginic acid, present in many laxative agents.
Pregnancy and Breastfeeding
- Bladderwrack is not recommended during pregnancy or lactation due to a lack of reliable scientific information and because of the presence of high levels of iodine and possible heavy metal contamination.
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.
Interactions with Drugs
- In theory, the high iodine content of bladderwrack may interfere with the function of drugs that act on the thyroid such as levothyroxine (Synthroid®, Levoxyl®). Use of bladderwrack and amiodarone may alter thyroid function due to high iodine levels in both agents. Use of iodine-containing agents such as bladderwrack or kelp may alter thyroid function when used with lithium. Other endocrine hormones, estrogen levels, and progesterone levels may be affected and therefore bladderwrack may interacte with hormonal drugs.
- Extracts of bladderwrack may cause lowered blood sugar. Caution is advised when using medications that may also lower blood sugar. Patients taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare provider. Medication adjustments may be necessary.
- Bladderwrack may have blood-thinning (anticoagulant) properties. Therefore, bladderwrack may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants ("blood thinners") such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®) .
- Laxative properties have traditionally been attributed to chronic use of bladderwrack and other brown seaweeds and may be due to the component alginic acid, present in many laxative agents. Combination with laxatives may cause an additive effect. In theory, due to thyroid stimulant properties, bladderwrack may cause additive effects if taken with stimulants. The presence of heavy metal contaminants in bladderwrack preparations, including arsenic, cadmium, chromium, or lead, may increase the risk of kidney toxicity if taken with drugs that cause kidney damage. Bladderwrack may interact with diuretics.
Interactions with Herbs and Dietary Supplements
- Extracts of bladderwrack may lower blood sugar levels. Caution is advised when using herbs or supplements that may also lower blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment.
- Bladderwrack may increase the risk of bleeding when taken with herbs and supplements that are believed to increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba , and fewer cases with garlic and saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases.
- Laxative properties have traditionally been attributed to the chronic use of bladderwrack and other brown seaweeds, and may be due to the component alginic acid, present in many laxative agents. Combination with laxatives may cause an additive effect.
- In theory, due to thyroid stimulant properties, bladderwrack may cause additive effects if taken with herbs or supplements with stimulant-type activity, such as caffeine, guarana, or ephedra (ma huang). The presence of heavy metal contaminants in bladderwrack preparations, including arsenic, cadmium, chromium, or lead, may increase the risk of kidney toxicity if taken with herbs or supplements that can cause kidney damage.
- In theory, bladderwrack may decrease iron absorption, especially if ingested for a prolonged period of time. Bladderwrack preparations contain variable levels of calcium, magnesium, potassium, sodium, vitamins, and minerals and may therefore increase corresponding blood levels. Bladderwrack may interact with diuretics.
- This information is based on a professional level monograph edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com): Ethan Basch, MD (Harvard Medical School); Heather Boon, B.Sc.Phm, PhD (University of Toronto); Dawn Costa, BA, BS (Natural Standard Research Collaboration); Ivo Foppa, MD, PhD (Harvard University); Sadaf Hashmi, MD, MPH (Johns Hopkins School of Hygiene and Public Health); Beth N. Kerbel, PharmD (Northeastern University); Michael Smith, MRPharmS, ND (Canadian College of Naturopathic Medicine); David Sollars, M.Ac, H.M.C. (New England School of Acupuncture); Shaina Tanguay-Colucci, BS (Natural Standard Research Collaboration); Catherine Ulbricht, PharmD (Massachusetts General Hospital); Wendy Weissner, BA (Natural Standard Research Collaboration), Jen Woods, BS (Natural Standard Research Collaboration).
Methodology details
- Amster E, Tiwary A, Schenker MB. Case report: potential arsenic toxicosis secondary to herbal kelp supplement. Environ Health Perspect 2007 Apr;115(4):606-8.
- Clark CD, Bassett B, Burge MR. Effects of kelp supplementation on thyroid function in euthyroid subjects. Endocr Pract 2003;9(5):363-369.
- Conz PA, La Greca G, Benedetti P, et al. Fucus vesiculosus: a nephrotoxic alga? Nephrol Dial Transplant 1998;13(2):526-527.
- Durig J, Bruhn T, Zurborn KH, et al. Anticoagulant fucoidan fractions from Fucus vesiculosus induce platelet activation in vitro. Thromb Res 1997;85(6):479-491.
- Eliason BC. Transient hyperthyroidism in a patient taking dietary supplements containing kelp. J Am Board Fam Pract 1998;11(6):478-480.
- Ellouali M, Boisson-Vidal C, Durand P, et al. Antitumor activity of low molecular weight fucans extracted from brown seaweed Ascophyllum nodosum. Anticancer Res 1993;13(6A):2011-2020.
- Lamela M, Anca J, Villar R, et al. Hypoglycemic activity of several seaweed extracts. J Ethnopharmacol 1989;27(1-2):35-43.
- Le Tutour B, Benslimane F, Gouleau MP, et al. Antioxidant and pro-oxidant activities of the brown algae, Laminaria digitata, Himanthalia elongata, Fucus vesiculosus, Fucus serratus and Ascophyllum nodosum. J Applied Phycology 1998;10(2):121-129.
- Müssig K, Thamer C, Bares R, et al. Iodine-induced thyrotoxicosis after ingestion of kelp-containing tea. J Gen Intern Med 2006 Jun;21(6):C11-4.
- Nishiyama S, Mikeda T, Okada T, et al. Transient hypothyroidism or persistent hyperthyrotropinemia in neonates born to mothers with excessive iodine intake. Thyroid 2004;14(12):1077-1083.
- Picco G, de Dios-Romero A, Albanell N, et al. [Regular intake of seaweed and hyperthyroidism]. Med Clin (Barc) 2006 Jul 1;127(5):199
- Pye KG, Kelsey SM, House IM, et al. Severe dyserythropoiesis and autoimmune thrombocytopenia associated with ingestion of kelp supplements. Lancet 1992;339(8808):1540.
- Shilo S, Hirsch HJ. Iodine-induced hyperthyroidism in a patient with a normal thyroid gland. Postgrad Med J 1986;62(729):661-662.
- 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.
- Teas J, Braverman LE, Kurzer MS, et al. Seaweed and soy: companion foods in Asian cuisine and their effects on thyroid function in American women. J Med Food 2007 Mar;10(1):90-100.
January 01, 2008.
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This evidence-based monograph was prepared by the Natural Standard Research Collaboration. The information provided should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. Talk to your health care provider before taking any prescription or over the counter drugs (including any herbal medicines or supplements) or following any treatment or regimen. Copyright© 2008 Natural Standard (www.naturalstandard.com). All Rights Reserved.
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