Seaweed

Seaweed/Drug Interactions:

  • GeneralGeneral: A report was published on interactions with drugs and clinical laboratory tests; however, further details are lacking (195; 196). Concerns over polypharmacy (herbs and medication use) were expressed in a letter; however, specific details related to seaweed are lacking (197).
  • AmiodaroneAmiodarone: In theory, concomitant use of seaweed and amiodarone may alter thyroid function due to high iodine levels in both agents.
  • Antiallergic agentsAntiallergic agents: In vitro, Sargassum hemiphyllum methanol extract inhibited an atopic allergic reaction and reduced effects of an induced anaphylactic reaction (198). In a review, phlorotannins from brown seaweeds were said to have antiallergic effects (1).
  • AntiarthriticsAntiarthritics: In cartilage explant culture in vitro, ventol, a constituent of Ecklonia cava, had antioxidant and anti-inflammatory effects (199).
  • AntiasthmaticsAntiasthmatics: Senevirathne et al. published a review on the antiasthmatic effects of marine algae (200). Further details are lacking.
  • AntibioticsAntibiotics: In vitro, a lectin-like mucopolysaccharide from bladderwrack was found to have activity against Candida guilliermondii and to inhibit growth of multiple Neisseria meningitidis and Escherichia coli strains (201).
  • Anticoagulants and antiplateletsAnticoagulants and antiplatelets: In human research, there was an increase in the activated partial thromboplastin time (p=0.01) and antithrombin III (p=0.03) following use of fucoidan, and a decrease in thrombin time (p=0.04) (113). In vitro, seaweeds have shown anticoagulant properties (110; 111; 202). Fucoidans have anticoagulant and thrombolytic properties (184; 110; 203; 111; 204; 205; 206; 207; 208; 113; 209).
  • AntidiabeticsAntidiabetics: In human research, consumption of a food containing carrageenan from seaweed decreased postprandial glycemic response and decreased the area under the curve for glucose vs. the food product without carrageenan (109). However, in human research, enrichment of bread with Ascophyllum nodosum resulted in a lack of effect on blood glucose levels (210), a blend of Ascophyllum nodosum and Fucus vesiculosus inhibited postchallenge plasma insulin levels, although the effect was lacking with glucose (211). Purified polyphenols from Ecklonia cava lacked significant effects on levels of blood glucose in overweight individuals (147). In animal research, extracts of Fucus vesiculosus caused significant hypoglycemia (108).
  • AntifungalsAntifungals: A lectin-like mucopolysaccharide isolated from F. vesiculosus has been found to be specific for complex carbohydrates. This mucopolysaccharide caused agglutination of the yeast Candida guilliermondii and inhibited the growth of C. guilliermondii by 99.2% (212). In vivo studies are lacking.
  • AntihelminthicsAntihelminthics: According to secondary sources, seaweed may interact with antihelminthic agents.
  • Anti-inflammatory agentsAnti-inflammatory agents: In an animal inflammation model, seaweed fucoidans inhibited leukocyte recruitment (204). Also, according to a review, the phlorotannins from brown seaweeds have anti-inflammatory effects (1).
  • Antihypertensive agentsAntihypertensive agents: According to a review, the phlorotannins from brown seaweeds have hypotensive effects (1). In human research, brown seaweed (Undaria pinnatifida) reduced blood pressure in patients with metabolic syndrome (114).
  • AntilipemicsAntilipemics: In human research, enrichment of bread with Ascophyllum nodosum resulted in a lack of effect on cholesterol levels (210); however, in human research, polyphenols from Ecklonia cava reduced total and LDL cholesterol, and increased HDL cholesterol (147). According to animal evidence, sodium alginate (soluble algae polysaccharide from the cell walls of brown algae) may lower lipid levels in the blood (213), and various topical seaweeds reduced levels of total and LDL cholesterol and triglycerides, while increasing HDL cholesterol (214).
  • AntineoplasticsAntineoplastics: Extracts of seaweeds, as well as constituents such as fucans and fatty acids, have shown anticancer effects, including antiproliferative and antiadhesive effects in vitro and in animal research (215; 216; 217; 202; 161; 218; 219; 204; 220).
  • Antiobesity agentsAntiobesity agents: Bladderwrack and other seaweed products are often marketed for weight loss. Although its anorectic properties have not been adequately evaluated in humans, according to reviews, the seaweed constituent fucoxanthin induces UCP1 in abdominal white adipose tissue mitochondria, resulting in fatty acid oxidation and heat production (221). The constituent alginic acid may be involved in the antiobesity effects of Laminaria japonica in animal triglyceride feeding studies (35). Also, in human research, enrichment of bread with Ascophyllum nodosum resulted in a subsequent reduction in intake of energy (210). In animal research, various seaweeds resulted in a reduced weight gain in animals fed a high-fat diet (214).
  • AntiparasiticsAntiparasitics: According to secondary sources, bladderwrack may have antiparasitic effects.
  • AntiretroviralsAntiretrovirals: In vitro, fractions of hot water extraction of polysaccharides and polyphenols from Fucus vesiculosus had anti-HIV effects such as HIV-induced syncytium formation and HIV reverse transcriptase enzyme activity (222). According to a review, constituents of marine macroalgae have anti-HIV effects (31). In vitro, fucoidan inhibited the cell-to-cell transmission of HTLV-1 (182). In human research, there was a 42.4% decrease in the proviral load with fucoidan use (182).
  • AntiviralsAntivirals: In vitro, an extract of Tasmanian Undaria pinnatifida inhibited herpes viruses; the extract was also mitogenic to human T cells (223). This extract increased healing rates in patients with active infections and helped patients remain asymptomatic. According to a review, mekabu fucoidan from Undaria pinnatifida had antiviral effects against influenza A virus in laboratory research (224).
  • Cardiovascular agentsCardiovascular agents: In animal research, fucoidan improved repair or myocardial tissue in a myocardial ischemia model perhaps by promoting revascularization (225). In animal research, a low-molecular-weight fucoidan prevented neointimal hyperplasia following aortic allografting (226). In animal research, injection of alginate into an old infarct improved cardiac remodeling and dysfunction (227). In a case report, mortality of a patient was deemed to be due to blood hemorrhaging from the stomach due to increased prostaglandin production following consumption of ogonori; symptoms prior to death included hypotension (100). In a case report, polymorphic ventricular tachycardia/ventricular fibrillation occurred in a patient taking a weight loss product containing seaweed (Fucus, as well as dandelion and boldo) (107).
  • Cholinesterase inhibitorsCholinesterase inhibitors: In a review, the potential neuroprotective effects of marine algae were discussed (42). Potential mechanisms of action include its potential to inhibit cholinesterase inhibitory activity and neuronal death.
  • CNS depressantsCNS depressants: There is a case report of arsenic-induced peripheral neuropathy in a 74 year-old woman taking kelp tablets (138). A 54 year-old woman with arsenic poisoning associated with kelp supplements experienced memory loss that improved once kelp was discontinued (139).
  • CNS stimulants (amphetamines, methylphenidate)CNS stimulants (amphetamines, methylphenidate): There is a case report of arsenic-induced peripheral neuropathy in a 74 year-old woman taking kelp tablets (138). A 54 year-old woman with arsenic poisoning associated with kelp supplements experienced memory loss that improved once kelp was discontinued (139).
  • CyclosporineCyclosporine: In animal research, fucoidan protected against cyclosporine-induced toxicity in the bone marrow and spleen (228).
  • Dermatologic agentsDermatologic agents: In human research, Fucus vesiculosus aqueous extract caused a significant decrease in skin thickness and a significant improvement in skin elasticity (229). In vitro, Furcellaria lumbricalis and Fucus vesiculosus stimulated procollagen I production (230). In vitro in a model of dermal wound repair, fucoidan inhibited transforming growth factor (TGF)-beta1-induced fibroblast proliferation (231).
  • DiureticsDiuretics: In theory, seaweed may decrease the effectiveness of diuretics due to its high sodium content. Seaweed may also contain potassium, increasing serum potassium levels.
  • Gastrointestinal agentsGastrointestinal agents: Iodine toxicity, which may occur with chronic bladderwrack use, may cause a brassy taste, increased salivation, and/or gastric irritation. A 54 year-old woman with arsenic poisoning associated with kelp supplements experienced fatigue, nausea, and vomiting that improved once kelp was discontinued (139). In animal research, a combination of products including fucoidan inhibited induced colitis; monocyte count was thought to play a role (232). In a clinical trial, adverse effects to fucoidan included diarrhea (N=4) (182).
  • HematologicsHematologics: A 54 year-old woman taking a vitamin and kelp tablets presented to her physician with abnormal bleeding and petechiae (112). She was diagnosed with autoimmune thrombocytopenic purpura with dyserythropoiesis, attributed to "contaminants" in the kelp preparation. Three months after withdrawal of the kelp supplement and treatment with immunoglobulin, prednisolone, and azathioprine, her dyserythropoiesis was reversed. In a case report, the mortality of a patient was deemed to be due to blood hemorrhaging from the stomach due to increased prostaglandin production following consumption of ogonori (100). In a case report, hemorrhagic cystitis was induced by Slim-Kombu? (containing kombu) (101).
  • Hormonal agentsHormonal agents: In human research, bladderwrack increased menstrual cycle length, and reduced beta-estradiol and increased progesterone levels (115). In human research, seaweed decreased serum estradiol (233).
  • ImmunostimulantsImmunostimulants: In vitro, polysaccharides from Laminaria saccharina, Laminaria digitata, Fucus evanescens, Fucus serratus, Fucus distichus, Fucus spiralis, and Ascophyllum nodosum inhibited P-selectin-mediated neutrophil-platelet adhesion (204). According to a review, the glucans found in seaweed have immunomodulating effects (23).
  • ImmunosuppressantsImmunosuppressants: In vitro, polysaccharides from Laminaria saccharina, Laminaria digitata, Fucus evanescens, Fucus serratus, Fucus distichus, Fucus spiralis, and Ascophyllum nodosum inhibited P-selectin-mediated neutrophil-platelet adhesion (204). According to a review, the glucans found in seaweed have immunomodulating effects (23).
  • Iron-containing agentsIron-containing agents: Theoretically, seaweed may reduce iron absorption after prolonged use.
  • LaxativesLaxatives: Laxative properties have traditionally been attributed to chronic use of bladderwrack and other brown seaweeds. Mechanistically, this may be due to the component alginic acid, a hydrophilic colloidal polysaccharide present in some laxative agents, as well as in bladderwrack.
  • Lithium carbonateLithium carbonate: In a patient treated with lithium, Fucus vesiculosus induced hyperthyroidism (128).
  • NephrotoxinsNephrotoxins: The presence of heavy metal contaminants in seaweed preparations, including arsenic, cadmium, chromium, or lead, may potentiate renal damage if taken with known nephrotoxic agents.
  • Neuroprotective agentsNeuroprotective agents: In a review, the potential neuroprotective effects of marine algae were discussed (42). Potential mechanisms of action include its potential to inhibit cholinesterase inhibitory activity and neuronal death.
  • Nonsteroidal anti-inflammatory agents (NSAIDs)Nonsteroidal anti-inflammatory agents (NSAIDs): In vitro, seaweeds have shown anticoagulant properties (110; 111; 202). Fucoidans have anticoagulant and thrombolytic properties (184; 110; 203; 111; 204; 205; 206; 207; 208; 113; 209). Also, in human research, oral intake of AquaminT reduced the use of NSAIDs in individuals with known osteoarthritis symptoms by 50% (234).
  • Osteoporosis drugsOsteoporosis drugs: In animal research, Sargassum horneri extracts had anabolic effects on bone metabolism (235).
  • Phototoxic agentsPhototoxic agents: According to a review, seaweed in foods may have photoprotective effects (236).
  • Respiratory agentsRespiratory agents: Allergic anaphylaxes to Laminaria, including shortness of breath and coughing, have been reported in case reports (164). In a case report, a six-month period of symptoms suggestive of bronchial asthma was found to be due to impaction of Japanese kelp (kombu) in the bronchi (188).
  • StimulantsStimulants: Theoretically, herbs or supplements with stimulant-like activity, such as caffeine, guarana, or ephedra (ma huang), may act synergistically with seaweed due to its purported hypermetabolic thyroid stimulant properties.
  • Thyroid hormones (thyroxine (T4), liothyroxine (T3), propylthiouracil (PTU), methimazole)Thyroid hormones (thyroxine (T4), liothyroxine (T3), propylthiouracil (PTU), methimazole): Based on the known sequelae of iodine toxicity, and as reported in case reports and reviews, the high iodine content in seaweeds may lead to hyperthyroidism, hypothyroidism, goiter, or myxedema (119; 120; 121; 122; 123; 124; 125; 126; 127; 99; 128; 129; 130; 131; 237).
  • WarfarinWarfarin: In human research, there was an increase in the activated partial thromboplastin time (p=0.01) and antithrombin III (p=0.03) following use of fucoidan, and a decrease in thrombin time (p=0.04) (113). In vitro, seaweeds have shown anticoagulant properties (110; 111; 202). Fucoidans have anticoagulant and thrombolytic properties (184; 110; 203; 111; 204; 205; 206; 207; 208; 113; 209). In a case report, there was a change in the international normalized ratio (INR) in a patient on warfarin who consumed sushi containing a large amount of asakusa-nori (238). Daughterty et al. published a report on dietary supplement and interactions with warfarin (239), and the topic was discussed in a review (240).

    • Seaweed/Herb/Supplement Interactions:

  • GeneralGeneral: A report was published on interactions with drugs and clinical laboratory tests; however, further details are lacking (195; 196). Concerns over polypharmacy (herbs and medication use) were expressed in a letter; however, specific details related to seaweed are lacking (197).
  • Antiallergic agentsAntiallergic agents: In vitro, Sargassum hemiphyllum methanol extract inhibited an atopic allergic reaction and reduced the effects of an induced anaphylactic reaction (198). According to a review, the phlorotannins from brown seaweeds have antiallergic effects (1).
  • AntiarthriticsAntiarthritics: In cartilage explant culture in vitro, ventol, a constituent of Ecklonia cava, had antioxidant and anti-inflammatory effects (199).
  • AntiasthmaticsAntiasthmatics: Senevirathne et al. published a review on the antiasthmatic effects of marine algae (200). Further details are lacking.
  • Anticoagulants and antiplateletsAnticoagulants and antiplatelets: In human research, there was an increase in the activated partial thromboplastin time (p=0.01) and antithrombin III (p=0.03) following use of fucoidan, and a decrease in thrombin time (p=0.04) (113). In vitro, seaweeds have shown anticoagulant properties (110; 111; 202). Fucoidans have anticoagulant and thrombolytic properties (184; 110; 203; 111; 204; 205; 206; 207; 208; 113; 209).
  • AntifungalsAntifungals: A lectin-like mucopolysaccharide isolated from F. vesiculosus has been found to be specific for complex carbohydrates. This mucopolysaccharide caused agglutination of the yeast Candida guilliermondii and inhibited the growth of C. guilliermondii by 99.2% (212). In vivo studies are lacking.
  • AntihelminthicsAntihelminthics: According to secondary sources, seaweed may interact with antihelminthic agents.
  • Anti-inflammatory agentsAnti-inflammatory agents: In an animal inflammation model, seaweed fucoidans inhibited leukocyte recruitment (204). Also, according to a review, the phlorotannins from brown seaweeds have anti-inflammatory effects (1).
  • Antihypertensive agentsAntihypertensive agents: According to a review, the phlorotannins from brown seaweeds have hypotensive effects (1). In human research, brown seaweed (Undaria pinnatifida) reduced blood pressure in patients with metabolic syndrome (114).
  • AntilipemicsAntilipemics: In human research, enrichment of bread with Ascophyllum nodosum resulted in a lack of effect on cholesterol levels (210); however, in human research, polyphenols from Ecklonia cava reduced total and LDL cholesterol, and increased HDL cholesterol (147). According to animal evidence, sodium alginate (soluble algae polysaccharide from the cell walls of brown algae) may lower lipid levels in the blood (213), and various topical seaweeds reduced levels of total and LDL cholesterol and triglycerides, while increasing HDL cholesterol (214).
  • AntimicrobialsAntimicrobials: In vitro, a lectin-like mucopolysaccharide from bladderwrack was found to have activity against Candida guilliermondii and to inhibit growth of multiple Neisseria meningitidis and Escherichia coli strains (201).
  • AntineoplasticsAntineoplastics: Extracts of seaweeds, as well as constituents such as fucans and fatty acids, have shown anticancer effects, including antiproliferative and antiadhesive effects in vitro and in animal research (215; 216; 217; 202; 161; 218; 219; 204; 220).
  • Antiobesity agentsAntiobesity agents: Bladderwrack and other seaweed products are often marketed for weight loss. Although its anorectic properties have not been adequately evaluated in humans, according to reviews, the seaweed constituent fucoxanthin induces UCP1 in abdominal white adipose tissue mitochondria, resulting in fatty acid oxidation and heat production (221). The constituent alginic acid may be involved in the antiobesity effects of Laminaria japonica in animal triglyceride feeding studies (35). Also, in human research, enrichment of bread with Ascophyllum nodosum resulted in a subsequent reduction in intake of energy (210); in animal studies, various seaweeds resulted in a reduced weight gain in animals fed a high-fat diet (214).
  • AntioxidantsAntioxidants: In animal research, various seaweeds had antioxidant effects and altered glutathione peroxidase activities (214). 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 (184). According to a review, the phlorotannins from brown seaweeds have antioxidant effects (1).
  • AntiparasiticsAntiparasitics: According to secondary sources, bladderwrack may have antiparasitic effects.
  • AntiretroviralsAntiretrovirals: In vitro, fractions of hot water extraction of polysaccharides and polyphenols from Fucus vesiculosus had anti-HIV effects such as HIV-induced syncytium formation and HIV reverse transcriptase enzyme activity (222). According to a review, constituents of marine macroalgae have anti-HIV effects (31).
  • AntiviralsAntivirals: In vitro, an extract of Tasmanian Undaria pinnatifida inhibited herpes viruses; the extract was also mitogenic to human T cells (223). This extract was also found to increase healing rates in patients with active infections and helped patients remain asymptomatic. According to a review, mekabu fucoidan from Undaria pinnatifida had antiviral effects against influenza A virus in laboratory research (224).
  • CalciumCalcium: A calcium product was made of absorbable algal calcium from oyster shell and seaweed (Cystophyllum fusiforme) and used in clinical trials (241; 242; 243; 244).
  • Cardiovascular agentsCardiovascular agents: In animal research, fucoidan improved repair or myocardial tissue in a myocardial ischemia model, perhaps by promoting revascularization (225). In animal research, a low-molecular-weight fucoidan prevented neointimal hyperplasia following aortic allografting (226). In animal research, injection of alginate into an old infarct improved cardiac remodeling and dysfunction (227).
  • Cholinesterase inhibitorsCholinesterase inhibitors: In a review, the potential neuroprotective effects of marine algae were discussed (42). Potential mechanisms of action include its potential to inhibit cholinesterase inhibitory activity and neuronal death.
  • CNS herbs and supplementsCNS herbs and supplements: There is a case report of arsenic-induced peripheral neuropathy in a 74 year-old woman taking kelp tablets (138). A 54 year-old woman with arsenic poisoning associated with kelp supplements experienced memory loss that improved once kelp was discontinued (139).
  • Dermatologic agentsDermatologic agents: In human research, Fucus vesiculosus aqueous extract caused a significant decrease in skin thickness and a significant improvement in skin elasticity (229). In vitro, Furcellaria lumbricalis and Fucus vesiculosus stimulated procollagen I production (230). In vitro in a model of dermal wound repair, fucoidan inhibited transforming growth factor (TGF)-beta1-induced fibroblast proliferation (231).
  • DiureticsDiuretics: In theory, seaweed may decrease the effectiveness of diuretics due to its high sodium content. Seaweed may also contain potassium, increasing serum potassium levels.
  • Gastrointestinal agentsGastrointestinal agents: Iodine toxicity, which may occur with chronic bladderwrack use, may cause a brassy taste, increased salivation, and/or gastric irritation. A 54 year-old woman with arsenic poisoning associated with kelp supplements experienced fatigue, nausea, and vomiting that improved once kelp was discontinued (139). In animal research, a combination of products including fucoidan inhibited induced colitis; monocyte count was thought to play a role (232).
  • HematologicsHematologics: A 54 year-old woman taking a vitamin and kelp tablets presented to her physician with abnormal bleeding and petechiae (112). She was diagnosed with autoimmune thrombocytopenic purpura with dyserythropoiesis, attributed to "contaminants" in the kelp preparation. Three months after withdrawal of the kelp supplement and treatment with immunoglobulin, prednisolone, and azathioprine, her dyserythropoiesis was reversed. In a case report, mortality of a patient was deemed to be due to blood hemorrhaging from the stomach due to increased prostaglandin production following consumption of ogonori (100). In a case report, hemorrhagic cystitis was induced by Slim-Kombu? (containing kombu) (101).
  • Hormonal agentsHormonal agents: In human research, bladderwrack increased menstrual cycle length, and reduced beta-estradiol and increased progesterone levels (115). In human research, seaweed decreased serum estradiol (233).
  • HypoglycemicsHypoglycemics: In human research, consumption of a food containing carrageenan from seaweed resulted in a decreased postprandial glycemic response and a decreased area under the curve for glucose vs. the food product without carrageenan (109). However, in human research, enrichment of bread with Ascophyllum nodosum resulted in a lack of effect on blood glucose levels (210); a blend of Ascophyllum nodosum and Fucus vesiculosus inhibited postchallenge plasma insulin levels, although this effect was lacking with glucose (211); and purified polyphenols from Ecklonia cava lacked significant effects on levels of blood glucose in overweight individuals (147). In animal research, extracts of Fucus vesiculosus caused significant hypoglycemia (108).
  • ImmunomodulatorsImmunomodulators: In vitro, polysaccharides from Laminaria saccharina, Laminaria digitata, Fucus evanescens, Fucus serratus, Fucus distichus, Fucus spiralis, and Ascophyllum nodosum inhibited P-selectin-mediated neutrophil-platelet adhesion (204). According to a review, the glucans, found in seaweed have immunomodulating effects (23).
  • IodineIodine: Seaweed may have high iodine content. There are case reports of transient hyperthyroidism associated with kelp products taken alone (119; 124).
  • IronIron: In theory, seaweed may decrease iron absorption, especially if ingested for a prolonged period of time.
  • LaxativesLaxatives: Laxative properties have traditionally been attributed to chronic use of bladderwrack and other brown seaweeds. Mechanistically, this may be due to the component alginic acid, a hydrophilic colloidal polysaccharide present in some laxative agents, as well as in bladderwrack.
  • Minerals calciummagnesiumpotassiumsodiumMinerals (calcium, magnesium, potassium, sodium): Seaweed preparations contain variable levels of calcium, magnesium, potassium, sodium, vitamins, and minerals.
  • NephrotoxinsNephrotoxins: The presence of heavy metals in seaweed preparations, including arsenic, cadmium, chromium, or lead, may potentiate renal damage if taken with known nephrotoxic agents (110; 111; 116).
  • Neuroprotective agentsNeuroprotective agents: In a review, the potential neuroprotective effects of marine algae were discussed (42). Potential mechanisms of action include its potential to inhibit cholinesterase inhibitory activity and neuronal death.
  • Osteoporosis agentsOsteoporosis agents: In animal research, Sargassum horneri extracts had anabolic effects on bone metabolism (235).
  • PectinPectin: In case reports, modified citrus pectin/alginates were used in heavy metal chelation and detoxification (8).
  • Phototoxic agentsPhototoxic agents: According to a review, seaweed in foods may have photoprotective effects (236).
  • PrebioticsPrebiotics: According to a review, polysaccharides found in seaweeds may act as prebiotics (245).
  • ProbioticsProbiotics: According to a review, polysaccharides found in seaweeds may act as prebiotics (245).
  • SeleniumSelenium: In vitro, selenium nanoparticles were fabricated in Undaria pinnatifida polysaccharide solutions for induction of apoptosis in a melanoma cell line (246).
  • SoySoy: In women, seaweed supplements decreased the soy-associated increase in serum levels of insulin-like growth factor (IGF-1) (247).
  • StimulantsStimulants: Theoretically, herbs or supplements with stimulant-like activity, such as caffeine, guarana, or ephedra (ma huang), may act synergistically with seaweed due to its purported hypermetabolic thyroid stimulant properties.
  • Thyroid agentsThyroid agents: Based on the known sequelae of iodine toxicity, and as reported in case reports and reviews, the high iodine content in seaweeds may lead to hyperthyroidism, hypothyroidism, goiter, or myxedema (119; 120; 121; 122; 123; 124; 125; 126; 127; 99; 128; 129; 130; 131; 237).
  • Vitamin AVitamin A: Vitamin A toxicity secondary to intake of high amounts of yellow-green vegetables has been reported in a case report; the effect of seaweed is unclear from this report, although the possibility exists given the high levels of beta-carotene in seaweed (104).

    • Seaweed/Food Interactions:

  • BreadBread: In human research, enrichment of bread with Ascophyllum nodosum resulted in a lack of effect on blood glucose levels (210)
  • Iodinecontaining foodsIodine-containing foods: Seaweed may have high iodine content. There are case reports of transient hyperthyroidism associated with kelp products taken alone (119; 124).
  • Ironcontaining foodsIron-containing foods: In theory, seaweed may decrease iron absorption, especially if ingested for a prolonged period of time.
  • Mineral calciummagnesiumpotassiumsodium-containing foodsMineral (calcium, magnesium, potassium, sodium)-containing foods: Bladderwrack preparations contain variable levels of calcium, magnesium, potassium, sodium, vitamins, and minerals.

    • Seaweed/Lab Interactions:

  • GeneralGeneral: A report was published on interactions with drugs and clinical laboratory tests; however, further details are lacking (195; 196).
  • Activated partial thromboplastin time (aPTT)Activated partial thromboplastin time (aPTT): In human research, there was an increase in the activated partial thromboplastin time (p=0.01) and antithrombin III (p=0.03) following use of fucoidan, and a decrease in thrombin time (p=0.04) (113). An additional ex vivo analysis using human plasma has demonstrated the ability of fucoidan to prolong the activated partial thromboplastin time (110). In vitro, most seaweed fucoidans had anticoagulant activity, based on activated partial thromboplastin time (204).
  • Blood pressureBlood pressure: According to a review, the phlorotannins from brown seaweeds have hypotensive effects (1). In human research, brown seaweed (Undaria pinnatifida) reduced blood pressure in patients with metabolic syndrome (114).
  • Body weightBody weight: Bladderwrack and other seaweed products are often marketed for weight loss. In human research, polyphenols from Ecklonia cava reduced body weight, body mass index (BMI), body fat ratio, and waist circumference (147). In human research, enrichment of bread with Ascophyllum nodosum resulted in a subsequent reduction in intake of energy (210). In animal studies, various seaweeds resulted in a reduced weight gain in animals fed a high-fat diet (214).
  • CalciumCalcium: According to secondary sources, bladderwrack may contain vitamins and minerals, including calcium, magnesium, potassium, and sodium, which may increase serum levels.
  • Coagulation panelCoagulation panel: In human research, there was an increase in the activated partial thromboplastin time (p=0.01) and antithrombin III (p=0.03) following use of fucoidan, and a decrease in thrombin time (p=0.04) (113). In vitro, seaweeds have shown anticoagulant properties (110; 111; 202). Fucoidans have anticoagulant and thrombolytic properties (184; 110; 203; 111; 204; 205; 206; 207; 208; 113; 209). In vitro, fucoidan increased activated partial thromboplastin time, prothrombin time, and thrombin time, and decreased antithrombin III (113). In vitro, fucoidan increased the activation of glutamic type plasminogen by tissue plasminogen activator (209).
  • CholesterolCholesterol: In human research, enrichment of bread with Ascophyllum nodosum resulted in a lack of effect on cholesterol levels (210); however, in human research, polyphenols from Ecklonia cava reduced total and LDL cholesterol, and increased HDL cholesterol (147). Based on animal evidence, sodium alginate (soluble algae polysaccharide from the cell walls of brown algae) may lower lipid levels in the blood (213), and various topical seaweeds reduced levels of total and LDL cholesterol and triglycerides, while increasing HDL cholesterol (214).
  • CytokinesCytokines: In vitro, Sargassum hemiphyllum methanol extract inhibited an atopic allergic reaction by regulating inflammatory mediators (interleukin-8 and tumor necrosis factor-alpha) (198).
  • Electrolytes (calciummagnesiumpotassiumsodiumElectrolytes (calcium, magnesium, potassium, sodium): Seaweed preparations contain variable levels of calcium, magnesium, potassium, sodium, vitamins, and minerals.
  • GlucoseGlucose: In human research, consumption of a food containing carrageenan from seaweed resulted in a decreased postprandial glycemic response and decreased area under the curve for glucose vs. the food product without carrageenan (109). However, in human research, enrichment of bread with Ascophyllum nodosum resulted in a lack of effect on blood glucose levels (210); a blend of Ascophyllum nodosum and Fucus vesiculosus inhibited postchallenge plasma insulin levels, although this effect was lacking with glucose (211); and purified polyphenols from Ecklonia cava lacked significant effects on levels of blood glucose in overweight individuals (147). In animal research, extracts of Fucus vesiculosus caused significant hypoglycemia (108).
  • Hormone panelHormone panel: In human research, bladderwrack increased menstrual cycle length, and reduced beta-estradiol and increased progesterone levels (115). In human research, seaweed decreased serum estradiol (233).
  • InsulinInsulin: In human research, a blend of Ascophyllum nodosum and Fucus vesiculosus inhibited postchallenge plasma insulin levels (211).
  • Insulin-like growth factorInsulin-like growth factor: In women, seaweed supplements decreased the soy-associated increase in serum levels of insulin-like growth factor (IGF-1) (247).
  • IronIron: In theory, seaweed may decrease iron absorption, especially if ingested for a prolonged period of time.
  • Liver enzymesLiver enzymes: In human research, polyphenols from Ecklonia cava decreased levels of serum alanine transaminase and serum aspartate transaminase (147).
  • MagnesiumMagnesium: According to secondary sources, bladderwrack may contain vitamins and minerals, including calcium, magnesium, potassium, and sodium, which may increase serum levels.
  • PotassiumPotassium: According to secondary sources, bladderwrack may contain vitamins and minerals, including calcium, magnesium, potassium, and sodium, which may increase serum levels.
  • Radioactive iodine uptakeRadioactive iodine uptake: In theory, seaweed may interfere with radioactive iodine uptake and thyroid function tests due to its iodine-induced alteration of thyroid function.
  • SodiumSodium: According to secondary sources, bladderwrack may contain vitamins and minerals, including calcium, magnesium, potassium, and sodium, which may increase serum levels.
  • Thyroid hormones (thyroxine; T4 and triiodothyronine; T3) levelsThyroid hormones (thyroxine; T4 and triiodothyronine; T3) levels: In human research, seaweed slightly decreased levels of T3 and T4, although they were still within normal limits, or it had a lack of effect on levels, depending on the length of ingestion (117).
  • Thyroid-stimulating hormone (TSH)Thyroid-stimulating hormone (TSH): In human research, seaweed increased TSH levels (148; 117).
  • Urinary iodineUrinary iodine: In human research, seaweed increased levels of urinary iodine (117).