Seaweed
Scientific Name(s):Over 9000 species exist, including Ascophyllum , Chondrus , Ecklonia , Fucus , Gelidium , Gracilaria , Laminaria , Phaeophycota , Pterocladia , and Rhodophyceae 1 , 2 , 3 , 4
Common Name(s): Brown seaweed , red seaweed , kelp , carrageenin , Irish moss 2 , 3
Clinical Overview
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Uses of Seaweed
Seaweed is used in calcium alginate dressings and for dilation of the cervix prior to gynecological procedures (although infections are a concern). There is limited information regarding its laxative, antibiotic, antifungal, and insecticide effects.
Seaweed Dosing
Seaweed fiber has been studied for mild hypertension at doses of 6-24 g daily. Calcium from seaweed and oyster shell has been studied in an osteoporosis trial at 900 mg daily.
Contraindications
Contraindications have not yet been identified.
Pregnancy/Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking. Avoid use.
Seaweed Interactions
Patients taking warfarin and consuming a large quantity of food containing seaweed may experience a change in INR because of seaweed's high vitamin K content.
Seaweed Adverse Reactions
Contact dermatitis, goiter, and, occasionally, GI effects.
Toxicology
Rare cases of potent inflammatory reactions, extreme GI symptoms resulting in death, and cholera.
Botany
Seaweeds are marine algae, saltwater-dwelling, simple organisms that fall into the general category of plants. Most of them are the red (6000), brown (2000), or green (1200) species and have root-like structures called holdfasts that serve an anchorage function. 4
History
For centuries, seaweed has been of botanical, industrial, and pharmaceutical interest. Because of the high nutrient content, seaweed has been used as a food throughout Asia. 3
Traditional Chinese medicine used hot water extracts of certain seaweeds in the treatment of cancer. Additionally, the Japanese and Chinese cultures have used seaweeds to treat goiter and other glandular problems since 300 BC. 5
The Romans used seaweeds in the treatment of wounds, burns, and rashes. 3 The Celts noted that ordinary seaweed contracted as it dried and then expanded with moisture. In Scotland during the 18th century, physicians used dried seaweed stem to successfully drain abdominal wall abscesses. They also inserted seaweed into the cervix in an attempt to treat dysmenorrhea. Many reports outline the use of seaweed to induce abortion. Seaweed was employed intravaginally for vaginal atresia and was used urethrally and rectally for strictures. 1
Chemistry
The major chemical components of seaweed are alginates, agars, and carrageenans. Alginates are cell wall constituents of brown seaweeds. They are chain-forming heteropolysaccharides composed of blocks of mannuronic acid and guluronic acid. The metal salts of alginic acid readily dissolve in cold water to yield viscous solutions. 4 Agars are polysaccharides derived from red seaweeds and consist of alternating D- and L-galactopyranose units. Carrageenan, in contrast to agar, is built up from D-galactopyranose units only. 4
Seaweed Uses and Pharmacology
Studies report that the seaweeds are used worldwide for many medicinal purposes. The brown seaweeds contain a polysaccharide fraction known as fucan sulfate that has antithrombin 6 and antiviral 7 activity. The red seaweeds have antiherpetic and laxative effects. 8 Furthermore, there are reports in the literature of antibiotic, antifungal, and insecticide properties associated with seaweeds. 3 It has been noted that their extracts exert a stimulatory effect on B lymphocytes and macrophages, which may be used clinically for the modulation of immune responses. 9 , 10
In addition to these reports, substantial evidence exists for the following effects:
Ripening of the cervixAnimal data
Research reveals no animal data for the use of seaweed for ripening of the cervix.
Clinical dataLaminaria tents have been used for many decades to dilate the uterine cervix. However, the technique fell into disrepute because of improper methods of sterilization and resulting uterine infection. With the use of gamma radiation for sterilization purposes, Laminaria tents once again were used in the 1970s for first- and second-trimester abortion. 11 Although the hydrophilic property of Laminaria may be considered the principal mechanism promoting cervical dilation, it also may alter levels of uterine prostaglandin F 2α . 12 Studies in the 1980s demonstrated that a combination of Laminaria with prostaglandin increased the success rate and decreased abortion time. 13 , 14 By the late 1980s, a synthetic tent had been developed, known as lamicel. This appeared to have greater convenience, lower rate of bleeding upon removal, lower cost per patient, and comparable efficacy. 15 Laminaria tents also have been used to ripen the cervix and induce labor. A small, randomized trial of 20 patients showed that Laminaria tents were more effective than PGE 2 vaginal suppositories at cervical dilation. It has been proposed that Laminaria tents could be used in patients when PGE 2 has failed, when patients are intolerant of PGE 2 , or where uterine contractions are undesirable. 16 However, studies also have illustrated problems associated with its use. Significant risk of maternal and neonatal infectious morbidity has been found. 17
Wound managementAnimal data
Research reveals no animal data for the use of seaweed for wound management.
Clinical dataA number of dressings and topical agents have evolved for use as a consequence of improved understanding of wound healing. Dressings now include alginates. These are naturally occurring polysaccharides found only in the brown seaweeds and come in the form of a loose, fibrous rope or pad. They are generally classified as hydrogels. Calcium alginate dressings are suitable for burns and extensive wounds where a normal dressing would be difficult to remove. 4 When applied to the wound, a network is formed around which a healthy scab may appear. The calcium ions found in the dressings interact with the sodium ions within the wound exudate to produce a fibrous gel. The hydrophilic gel provides a barrier to contamination and a moist wound environment that allows gaseous exchange. The bandage may be removed with a sodium chloride solution, which renders the alginate soluble in water. 18
Other usesAnticancer effects
Breast cancer rates show dramatic differences in worldwide distribution; it appears that behavioral factors are involved. 19 Epidemiologic studies have shown that the rates of breast cancer incidence in premenopausal women in Japan is about 3 times lower and in postmenopausal women 9 times lower than those found in the United States. Not only do fewer Japanese women develop breast cancer, but when they do, they live longer than their counterparts in the United States. One explanation for this may be the much higher consumption of dietary seaweed in Japan. 5 The estimated per capita intake of seaweed in Japan ranges from 4.9 to 7.3 g/day. 5
Research has led to the isolation of a number of polysaccharides from edible brown kelp seaweeds ( Laminaria angustata , japonica , and religiosa ), which slow the development of various induced cancers (in vitro). Their proposed mechanism of action is enhancement of the immunological defense of the organism against the carcinogen. Other explanations are that Laminaria is a source of nondigestible fiber (thereby increasing fecal bulk and decreasing bowel transit time) and that it contains an antibiotic substance that may influence fecal ecology. 19
Antihypertensive effectsLow-sodium diets are widely reported to reduce blood pressure and are recommended by the American College of Cardiology in the treatment of mild hypertension. Seaweed preparations have been shown to decrease blood pressure by a mechanism involving ion exchange. In a double-blind, crossover study, 62 middle-aged patients with mild hypertension were given a potassium-releasing seaweed preparation. Mean blood pressure was reduced from 112 to 101 mm Hg after ingestion of 12 g/day seaweed. 20 However, evidence has not shown that seaweed reduces mortality; therefore, seaweed cannot be recommended for the treatment of hypertension.
Dosage
Seaweed fiber has been studied for mild hypertension at doses of 6-24 g daily. Calcium from seaweed and oyster shell has been studied in an osteoporosis trial at 900 mg daily. 21
Pregnancy/Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking. Avoid use.
Interactions
A single case report describes a change in the international normalized ratio (INR) in a patient taking warfarin who consumed a large quantity of sushi that contained a seaweed. This was thought to be caused by the high vitamin K content of the seaweed. 22
Adverse Reactions
Excessive intake of dried seaweed has been reported to cause carotenodermia (yellowing of the skin). Hypercarotenemia is caused by excessive intake of carotene-rich vegetables or drinks. 23
Seaweed is a rich source of iodine. In Japan, where seaweed is widely consumed, a number of cases of diet-induced goiter have been reported. The goiters appear to be only cosmetic and elimination of seaweed from the diet generally leads to shrinkage or disappearance of the goiter. Iodine concentrations in seaweed-containing dietary supplements vary widely. In some cases, the US maximum safe iodine intake of 1000 mcg/day easily could be exceeded. Whether this could prove harmful is difficult to ascertain because susceptibility to the effects of a high intake of iodine appears to vary among individuals. 24
Toxicology
The blue-green algae Lyngbya majuscala is known to be toxic and to colonize seaweeds that are common throughout the Pacific, Indian, and Caribbean oceans. There are a number of reports of this algae causing contact dermatitis, commonly known as “stinging seaweed dermatitis.” An isolate from the algae, debromoaplysiatoxin, is a very potent inflammatory agent, producing a follicular, papular, and pustular reaction in minute concentrations. 25
Two other seaweeds, Gracilaria coronopifolia and G. tsudai , usually are considered nontoxic but occasionally may produce poisons associated with GI symptoms when ingested. Extreme cases have resulted in death. 26 There also has been a report of cholera associated with eating raw seaweed. 27
Bibliography
1. Johnson N. Seaweed and its synthetic analogues in obstetrics and gynecology 450 BC–AD 1990. J R Soc Med . 1990;83:387-389.2. Weber KT. Snakes and seaweed: a case of the swollen organ. Cardiovasc Res . 1995;29:457-462.
3. Abdussalam S. Drugs from seaweeds. Med Hypotheses . 1990;32:33-35.
4. http://www.seaweed.ie/defaultsunday.html
5. Hocman BG. Prevention of cancer: vegetables and plants. Comp Biochem Physiol . 1989;93:201-212.
6. Nishino T, Yokoyama G, Dobashi K, Fujihara M, Nagumo T. Isolation, purification, and characterization of fucose-containing sulfated polysaccharides from the brown seaweed Ecklonia kurome and their blood-anticoagulant activities. Carbohydr Res . 1989;186:119-129.
7. Feldman SC, Reynaldi S, Stortz CA, Cerezo AS, Damont EB. Antiviral properties of fucoidan fractions from Leathesia difformis . Phytomedicine . 1999;6:335-340.
8. Carlucci MJ, Pujol CA, Ciancia M, et al. Antiherpetic and anticoagulant properties of carrageenans from the red seaweed Gigartina skottsbergii and their cyclized derivatives: correlation between structure and biological activity. Int J Biol Macromol . 1997;20:97-105.
9. Liu JN, Yoshida Y, Wang MQ, Okai Y, Yamashita U. B-cell stimulating activity of seaweed extracts. Int J Immunopharmacol . 1997;19:135-142.
10. Shan BE, Yoshida Y, Kuroda E, Yamashita U. Immunomodulating activity of seaweed extract on human lymphocytes in vitro. Int J Immunopharmacol . 1999;21:59-70.
11. Tohan N, Tejani NA, Varanasi M, Robins J. Ripening of the term cervix with Laminaria . Obstet Gynecol . 1979;54:588-590.
12. Ye BL, Yamamoto K, Tyson JE. Functional and biochemical aspects of Laminaria use in first-trimester pregnancy termination. Am J Obstet Gynecol . 1982;142:36-39.
13. Karim SM, Ratnam SS, Lim AL, Yeo KC, Choo HT. Termination of second trimester pregnancy with Laminaria and intramuscular 16 phenoxy-ω-17,18,19,20 tetranor PGE 2 methylsulfonylamide (sulprostone)—a randomised study. Prostaglandins . 1982;23:257-263.
14. Chowdhury NN, Bulusu R. Adjunctive use of Laminaria tents for termination of early mid-trimester pregnancy with intramuscular 15(S)-15-methyl PGF 2 alpha. Asia Oceania J Obstet Gynaecol . 1983;9:173-179.
15. Grimes DA, Ray IG, Middleton CJ. Lamicel versus Laminaria for cervical dilation before early second-trimester abortion: a randomized clinical trial. Obstet Gynecol . 1987;69:887-890.
16. Jeeva MA, Dommisse J. Laminaria tents or vaginal prostaglandins for cervical ripening: a comparative trial. S Afr Med J . 1982;61:402-403.
17. Kazzi GM, Bottoms SF, Rosen MG. Efficacy and safety of Laminaria digitata for preinduction ripening of the cervix. Obstet Gynecol . 1982;60:440-443.
18. Nelson EA, Bradley MD, Cullum NA. Dressings and topical agents for arterial leg ulcers (Cochrane Protocol). In: The Cochrane Library, Issue 2, 2002. Oxford, England: Update Software.
19. Teas J. The dietary intake of Laminaria , a brown seaweed, and breast cancer prevention. Nutr Cancer . 1983;4:217-222.
20. Krotkiewski M, Aurell M, Holm G, Grimby G, Szczepanik J. Effects of a sodium-potassium ion-exchanging seaweed preparation in mild hypertension. Am J Hypertens . 1991;4:483-488.
21. Fujita T, Ohue T, Fujii Y, Miyauchi A, Takagi Y. Heated oyster shell-seaweed calcium (AAA Ca) on osteoporosis. Calcif Tissue Int . 1996;58:226-230.
22. Bartle WR, Madorin P, Ferland G. Seaweed, vitamin K, and warfarin. Am J Health Syst Pharm . 2001;58:2300.
23. Nishimura Y, Ishii N, Sugita Y, Nakajima H. A case of carotenodermia caused by a diet of the dried seaweed called Nori. J Dermatol . 1998;25:685-687.
24. Norman JA, Pickford CJ, Sanders TW, Waller M. Human intake of arsenic and iodine from seaweed-based food supplements and health foods available in the UK. Food Addit Contam . 1988;5:103-109.
25. Izumi AK, Moore RE. ( Lyngbya majuscala ) dermatitis. Clin Dermatol . 1987;5:92-100.
26. Marshall KL, Vogt RL. Illness associated with eating seaweed, Hawaii, 1994. West J Med . 1998;169:293-295.
27. Vugia DJ, Shefer AM, Douglas J, Greene KD, Bryant RG, Werner SB. Cholera from raw seaweed transported from the Philippines to California. J Clin Microbiol . 1997;35:284-285.
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