Sargassum: A Comprehensive Reference Article
1. Identity, Taxonomy, and Natural Sources
Sargassum is a genus of brown seaweed (Phaeophyceae) in the family Sargassaceae, containing approximately 400 species. Brown seaweeds (class Phaeophyceae) are typically the largest and most complex of all algae; species of the genus Sargassum belong to the class Phaeophyceae, family Sargassaceae. Sargassum is found throughout all oceans and consumed as food and medicine in many cultures.
Among the hundreds of recognized species, those most prominent in medical and nutritional research include Sargassum pallidum (Turn.) C. Ag., Sargassum fusiforme (Harvey) Setchell (also known historically as Hizikia fusiforme, traded under the name hijiki), Sargassum fulvellum, Sargassum muticum, Sargassum horneri, Sargassum siliquastrum, Sargassum polycystum, Sargassum hemiphyllum, and Sargassum naozhouense, among many others. S. siliquastrum, S. muticum, S. hemiphyllum, S. polycystum, and S. vachellianum are well-recognized in Traditional Chinese Medicine.
In Traditional Chinese Medicine (TCM), the seaweed is known by the Chinese name Hai Zao (海藻). Sargassum pallidum and related species are common marine plants described as typical Chinese herbs used as both medicine and food, widely distributed in China, exhibiting biological properties such as antioxidant, hypolipidemic, antitumor, and hypoglycemic effects.
Only 78 of the 400 identified Sargassum species have been studied for their phytochemical and pharmacological properties, highlighting that the genus remains substantially under-researched despite its long history of human use.
2. Common Forms and Preparations
Sargassum is commercially and therapeutically available in several forms. The seaweed has historically been utilized in East Asia, primarily in Japan, China, and Korea, where it is collected off the coasts and traditionally sold fresh or dried. In pharmaceutical and supplementary contexts, dried whole thallus, powdered material, aqueous decoctions, ethanolic extracts, and isolated polysaccharide fractions (notably fucoidan and alginate) are the primary forms encountered.
In TCM, Hai Zao can also be taken as a wine-soaked preparation, ground into powder, or formed into pills. It is typically rinsed with fresh water before use to reduce excess salt, cut into segments after being briefly softened, and then dried before storage or decoction. Modern supplement manufacturers produce standardized capsules, tablets, and liquid extracts of various Sargassum species or their isolated constituents such as fucoidan or fucoxanthin.
3. Traditional and Historical Use
East Asia: China
For nearly 2,000 years, Sargassum spp. have been used in Traditional Chinese Medicine to treat a variety of diseases including thyroid disease, such as goitre. Known as Hai Zao, its use in TCM has been documented since at least the eighth century A.D. In TCM it is characterized as having a cold nature and a salty, bitter taste. Documented in ancient Chinese medical texts, Sargassum was revered for its ability to soften hard masses, dissipate nodules, and promote healthy fluid metabolism; it was traditionally employed to address conditions such as goiter, edema, scrofula, and phlegm accumulation.
Sargassum pallidum is a traditional Chinese marine medicinal material primarily found in coastal regions; with a long history of medicinal use in China, it is commonly employed to treat conditions such as goiter, hyperplasia of mammary glands, hypertension, and obesity.
Historically, Sargassum was seldom used alone; instead, it was combined with other botanicals to enhance its therapeutic effects. Classic TCM formulas, such as Hai Zao Yu Hu Tang, blend Sargassum with herbs like Kun Bu (Laminaria), Chuan Bei Mu (Fritillaria), and Ban Xia (Pinellia) to target thyroid conditions.
Brown seaweed, especially Sargassum species, has been one of the important ingredients in the traditional medicine of East Asian communities; some Sargassum species have been utilized for generations by Chinese and Korean people to treat several inflammation-associated health problems, such as painful scrotum, edema, liver organ swelling, and chronic bronchitis.
Other Cultures
Sargassum is one of the largest and most diverse genera of brown seaweeds; many species have long been part of human culture with applications as food, feed, and remedies in folk medicine. Sargassum naozhouense, for example, is a brown seaweed used in folk medicine and applied for thousands of years in Zhanjiang, Guangdong province, China. In Hawaii, Sargassum echinocarpum is the only seaweed used in a ho'o pono pono (forgiveness ceremony).
4. Key Constituents and Active Compounds
Bioactive compounds — currently about 200 identified — such as meroterpenoids, phlorotannins, fucoidans, sterols, and glycolipids have been identified from this genus. Polysaccharides, fatty acids, phytosterols, phlorotannins, and meroterpenoids are considered to be the major chemical components of Sargassum.
4.1 Proximate Composition
On a dry weight basis, S. naozhouense was found to be constituted of approximately 35.18% ash, 11.20% protein, 1.06% lipid, and 47.73% total carbohydrate, with the main carbohydrate being water-soluble polysaccharide. The protein analysis indicated the presence of essential amino acids, accounting for 36.35% of protein content. The most abundant fatty acids were C14:0, C16:0, C18:1, and C20:4, and the ash fraction indicated the presence of essential minerals and trace elements including Fe, Zn, and Cu.
Analyses of Caribbean Sargassum spp. have confirmed a broadly similar compositional profile: the seaweeds are mainly composed of alginates (17.75–30.19% DW), glucan (14.59–22.00% DW), minerals (14.48–19.86% DW), and fucan (8.21–12.63% DW), with low contents of lipid (0.40–1.10% DW), mannitol (1.95–2.80% DW), and polyphenol; the major fatty acid is palmitic acid.
4.2 Polysaccharides: Fucoidan and Alginate
Fucoidans are sulfated anionic polysaccharides isolated from the cell walls of marine brown algae; their structural complexity diverges in the degree of branching, type of functional groups, degree of sulfation, fine structure, and kind of bonds. They are generally composed of sulfate groups and fucose with minor proportions of xylose, uronic acids, mannose, arabinose, and galactose.
The S. siliquosum fucoidan was identified as a galactofucoidan composed of sugars, uronate, and sulfate at a ratio of 12:1:4; structural analysis revealed the purified fucoidan consisted of a carbohydrate chain composed of (1→3)-linked or (1→4)-linked L-fucose residues, with sulfate groups at C-2 and C-4 positions, with galactose residues serving as branch points.
IR analysis has revealed that polysaccharides from S. naozhouense may include both alginates and fucoidan.
4.3 Phlorotannins
Apart from high nutritional value, Sargassum seaweeds are also a well-known reservoir of natural antioxidant compounds of great interest, including polyphenols, carotenoids, meroterpenoids, phytosterols, and several others. Phlorotannins are polyphenolic compounds unique to brown algae; these include flavonoids, hydroxycinnamic acids, stilbenes, and phlorotannins — polyphenols which are polymers of phloroglucinol units linked by ether or phenyl bonds.
4.4 Carotenoids: Fucoxanthin
The brown alga S. siliquastrum has been shown to possess a variety of bioactive metabolites including sulfated polysaccharides, phlorotannins, fucoxanthin, sargachromanols, and sargaquinoic acid. Fucoxanthin is a carotenoid pigment responsible in part for the characteristic brownish color of these algae, and has attracted significant attention for its antidiabetic and anti-obesity properties.
4.5 Meroterpenoids, Sterols, and Alkanes
Chemical characterization of S. pallidum identified a total of 48 constituents, including fatty acids, alkaloids, terpenoids, amino acids, and sterols; two compounds — Aurantiamide and Linoleic acid — were subjected to detailed fragmentation analysis. Recent studies have shown that S. fusiforme contains significantly high amounts of alkanes (eicosane, tetracosane, dotriacontane, and tritetracontane) and fatty acid-natured hydrocarbons; eicosane, docosane, and tetracosane have been identified as active components with potent biological effects.
4.6 Iodine Content
A significant practical constituent is iodine. The iodine content in Sargassum spp. can occasionally exceed regulatory thresholds, with levels of up to 6,000 ppm having been reported, which is not uncommon for brown seaweed. This high iodine content has historically been the primary rationale for its use in thyroid disorders, though modern evidence has complicated this interpretation (see Section 6.1).
5. Mechanisms of Action
5.1 Anti-inflammatory Mechanisms
Low molecular weight fucoidan (SCF) isolated from Sargassum confusum significantly increased cell viability while decreasing intracellular reactive oxygen species (ROS) production in TNF-α/IFN-γ-stimulated HaCaT keratinocytes. Sargaquinoic acid isolated from S. siliquastrum has been shown to exert anti-inflammatory effects on NO production in LPS-induced macrophages via inhibiting NF-κB and c-Jun N-terminal kinase pathways. The action mechanism of sargachromanol G from S. siliquastrum on inflammatory responses has been examined in LPS-stimulated RAW 264.7 macrophages.
5.2 Antioxidant Mechanisms
The antioxidant and potential inhibitory capacity of matrix metalloproteinases has been demonstrated from phlorotannin-type polyphenolic and fucoidan-type polysaccharide extracts obtained from S. filipendula. DPPH and ABTS free radical scavenging activities of S. horneri extract were significantly increased in a concentration-dependent manner, indicating that S. horneri contains bioactive compounds such as phenols and flavonoids with excellent antioxidant activity. Studies have concluded that the greater the amount of sulfate in the fucoidan, the greater the antioxidant activity.
5.3 Anticancer Mechanisms
Using in vitro models with DLD-1 and SW480 colon cancer cell lines, fucoidan extracted from S. fusiforme was observed to arrest cancer cells in the G0/G1 phase in a dose-dependent manner; furthermore, the expression of cell cycle proteins Cdk2 and cyclin E1 were inhibited, while an increase in expression of p21 and apoptosis-related proteins including PARP, caspase 3, and Cyt-c was observed.
Although clinical trials investigating the antitumor effects of fucoidan in humans are limited, evidence from studies on tumor cells and their microenvironments suggests that fucoidan possesses significant antitumor activity.
5.4 Immunomodulatory Mechanisms
Although the mechanisms of action are still not fully clear, the pharmacological activities of Sargassum could be mainly attributed to the major biologically active metabolites, meroterpenoids, phlorotannins, and fucoidans. The contribution of iodine in Sargassum for treating thyroid-related diseases appears to have been overestimated. The bioactive compounds in Sargassum spp. appear to play a role as immunomodulators and could be useful in the treatment of thyroid-related diseases such as Hashimoto's thyroiditis.
5.5 Antidiabetic Mechanisms
Treatment of insulin-resistant HepG2 cells with S. horneri extract resulted in a concentration-dependent decrease in oxidative stress and increased intracellular glucose uptake and glycogen content; the treatment upregulated expression of IRS-1, AKT, and GLUT4 — which are suppressed in insulin resistance — to a similar degree as metformin. Polysaccharide fractions from S. fusiforme (SFP-2) have been shown to control postprandial hyperglycemia by inhibiting the activity of digestive enzymes in rats.
6. Scientific Evidence by Area of Use
6.1 Thyroid Health and Goiter
The most historically prominent therapeutic use of Sargassum is in the management of goiter. The primary traditional use of sargassum seaweed is to treat goiters — nodules in the neck caused by enlargement of the thyroid gland. The thyroid requires iodine to produce thyroxin, which regulates body metabolism; when insufficient iodine is consumed in the diet, the thyroid gland enlarges.
Evidence assessment: For nearly 2,000 years, Sargassum spp. have been used in TCM to treat thyroid disease, including goitre. However, modern systematic review has complicated the simple iodine-replacement explanation: the therapeutic effects of Sargassum spp. are scientifically plausible and may be explained partially by key in vivo and in vitro pharmacological activities such as anticancer, anti-inflammatory, antibacterial, and antiviral activities. Further research is required to determine both the preventative and therapeutic role of Sargassum spp. in thyroid health. Human clinical trial evidence specific to thyroid endpoints remains limited; no high-quality randomized controlled trials in humans have been identified in the peer-reviewed literature. When using Hai Zao for its iodine content in thyroid disorders, practitioners note that it may temporarily suppress hyperthyroid symptoms but cannot treat the underlying condition long-term; in patients with hyperthyroidism, iodine-rich herbs like Hai Zao should generally be avoided.
6.2 Anti-inflammatory Activity
Preclinical (in vitro/in vivo) evidence: Studies of crude lipid extracts of S. ilicifolium obtained from four different coastal areas in Indonesia demonstrated that RAW 264.7 macrophage cells treated with the extracts (12.5–50 µg/mL) significantly suppressed nitric oxide production after lipopolysaccharide stimulation, in both pre-incubated and co-incubated cell culture models; the anti-inflammatory effect was most marked in the pre-incubated model.
Levels of nitrites and cytokines (PGE2, TNF-α, and IL-6), which mediate pro-inflammatory effects, were significantly inhibited by treatment with S. horneri extract. General composition analysis of S. macrocarpum indicated that its hot-water extract contains more carbohydrates and polyphenols than ethanol extract, and monosaccharide composition analysis suggested that fucose-containing sulfated polysaccharide and β-glucan might be potent anti-inflammatory candidates.
Evidence strength: The anti-inflammatory evidence base is predominantly preclinical — cell culture and rodent models. No published human clinical trials specifically examining Sargassum extract as an anti-inflammatory intervention in a clinical population have been identified at the time of this writing. The mechanistic data are promising but require translation to human studies.
6.3 Antioxidant Activity
Preclinical evidence: Antioxidant capacity of S. filipendula extracts was evaluated using the methyl linoleate model for inhibition of lipid peroxidation and free radical scavenging capacity; the extracts exhibited high scavenging capacity of radical species and inhibition of diene conjugate formation. Sargassum muticum is known to produce molecules with potent antioxidant properties; studies have evaluated whether fractions of S. muticum presented antioxidant and cytoprotective potential on human MCF-7 cells when exposed to H₂O₂, as an oxidative stress model, and investigated mechanisms including mitochondrial membrane potential and Caspase-9 activity.
Many authors have described applications of polysaccharides and phlorotannins from Sargassum, including bone growth, antiviral, anti-inflammatory, immunomodulatory, anticoagulant, anticancer and antiproliferative activities, and recent studies have demonstrated their potential for prevention of premature skin aging through antioxidant and anti-enzymatic activities.
Evidence strength: Antioxidant activity is one of the most consistently demonstrated properties of Sargassum extracts, with robust in vitro evidence across multiple species and extraction methods. However, clinical trials measuring antioxidant endpoints in humans remain very limited.
6.4 Antidiabetic and Metabolic Effects
Preclinical evidence: Sargassum fusiforme alginate (SF-Alg) was evaluated in high-fat diet/streptozotocin-induced type 2 diabetic mice; SF-Alg intervention was found to significantly reduce fasting blood glucose, triglycerides, and total cholesterol, while increasing high-density lipoprotein cholesterol and improving glucose tolerance.
Sargassum hystrix extracts (SHE) at 200, 300, and 400 mg/kg were administered orally to streptozotocin-induced diabetic rats once daily for 15 days; preprandial and postprandial glucose levels in the group treated with SHE at 300 mg/kg were significantly reduced compared to the diabetes group, and levels of triglycerides and cholesterol also differed significantly.
Both free and encapsulated fucoxanthin from Sargassum angustifolium could decrease fasting blood glucose and increase plasma insulin level, similar to metformin; total cholesterol, triglyceride, and low-density lipoprotein were lower in treated groups, confirming an anti-obesity effect of fucoxanthin by regulating lipid profile parameters.
Polysaccharide fractions from S. fusiforme controlled postprandial hyperglycemia by inhibiting the activity of digestive enzymes; SFP-2 showed better regulatory effects on body weight, food intake, and levels of total cholesterol, triglycerides, LDL-C, and free fatty acid in diabetic rats.
Evidence strength: The antidiabetic evidence is substantial at the preclinical level, spanning multiple species, rodent models, and isolated compound studies. Among identified metabolites, quercetin 3-O-glucuronide exhibits potent antioxidant and α-glucosidase inhibitory activities, suggesting it may serve as the primary hypoglycemic and antioxidant component in S. pallidum polyphenols. However, human clinical trial data are absent from the published literature; all robust glycemic evidence is from animal or in vitro models.
6.5 Anticancer and Antitumor Activity
Preclinical evidence: Among Sargassum spp. grown off the Korean coast, the anticancer effects of five species (S. fulvellum, S. hemiphyllum, S. horneri, S. macrocarpum, and S. miyabei) have been studied in vitro using cell lines involving breast cancer (MDA-MB-231, MDA-MB-453, and MCF7), lung cancer (A549 and H1299), colon cancer (HCT116, SW620, HT-29, DLD-1, and CT26), prostate cancer (PC3 and DU145), gastric cancer (AGS), and cervical cancer (HeLa).
Polysaccharides obtained from S. fusiforme showed significant antitumor activity both in vitro and in vivo, and improved immune function in tumor-bearing mice. Natural bioactive polysaccharides are considered promising anticancer agents due to their notable anticancer activities and low side effects; anticancer mechanisms include inducing tumor cell apoptosis, inhibiting metastasis and angiogenesis, and modulating antioxidant signaling pathways.
Evidence strength: Although clinical trials investigating the antitumor effects of fucoidan in humans are limited, evidence from studies on tumor cells and their microenvironments suggests that fucoidan possesses significant antitumor activity. The field currently lacks human interventional data from randomized controlled trials, and the anticancer evidence must be characterized as preclinical and preliminary.
6.6 Antiviral Activity
Preclinical evidence: IR analysis of polysaccharides from cultivated S. naozhouense revealed alginates and fucoidan; the polysaccharides possessed strong antiviral activity against HSV-1 in vitro with an EC₅₀ of 8.92 μg/mL. Eicosane, docosane, and tetracosane — active components from S. fusiforme — have been identified with potent anti-RSV effects; these compounds have been reported with numerous biological properties including antifungal, antibacterial, and antitumor activities.
Evidence strength: Antiviral activity is demonstrated in vitro and in limited in vivo models. Human clinical evidence is absent. All conclusions remain preliminary.
6.7 Hypolipidemic Effects
Preclinical evidence: The purpose of a study involving Sargassum crassifolium was to obtain natural drugs from brown seaweed as antiatherosclerosis candidates through the study of hypolipidemic mechanisms of action, using a dyslipidemia rat model fed a high-fat diet and doses of crude fucoidan at 100, 200, and 400 mg/kg body weight. Crude fucoidan demonstrated hypolipidemic activity in the dyslipidemic mouse model. SF-Alg intervention significantly reduced fasting blood glucose, triglycerides, and total cholesterol while increasing HDL-C in type 2 diabetic mice.
Evidence strength: Hypolipidemic activity is supported by multiple animal studies across several species. No randomized controlled human trial data have been identified. Evidence remains preclinical.
6.8 Neuroprotective Activity
Preclinical evidence: Recent studies indicate that various compounds derived from Sargassum have significant neuroprotective effects in cellular and mouse models; the neuroprotective activity of fucoxanthin extracted from S. oligocystum was evaluated in rat C6 glial cells, which were pretreated with fucoxanthin and subsequently exposed to hydrogen peroxide — treatment increased cell viability by over 90% compared to the control, and glutathione peroxidase activity increased compared to cells treated only with hydrogen peroxide.
Heteropolysaccharides extracted from Sargassum integerrimum, S. maclurei, S. naozhouense, S. hemiphyllum, and S. fusiforme showed that neuroprotective activities varied according to the structure of the polysaccharides.
Evidence strength: Neuroprotective evidence is entirely preclinical (cell line and animal models). No human trials have been identified.
6.9 Anticoagulant Activity
Sulfated polysaccharides from Sargassum fulvellum showed anticoagulant activity in preclinical studies. Fucoidans are heterologous polysaccharides from brown macroalgae known for their biological activity including anticancer, antiangiogenic, immunomodulation, and antiviral properties. The structural features of fucoidan — particularly its sulfation pattern and degree of branching — are thought to underlie anticoagulant properties through mechanisms analogous to heparin, though the evidence base is exclusively preclinical.
6.10 Skin and Dermocosmetic Applications
The antioxidant and potential inhibitory capacity of matrix metalloproteinases of phlorotannin and fucoidan extracts from S. filipendula were evaluated; matrix metalloproteinase inhibition potential was measured by collagenase and elastase inhibition tests, and the extracts exhibited high scavenging capacity and inhibition of thiobarbituric acid reactive substances. These findings suggest potential applications in cosmeceutical formulations targeting skin aging, though no human clinical validation data were located.
7. Body Systems Associated with Sargassum
- Endocrine system (thyroid): The most emblematic medicinal application of Sargassum seaweeds is, unquestionably, the treatment of thyroid-related disorders such as goiter, mostly due to their high content of iodine.
- Immune system: Immunomodulatory activity via fucoidan-mediated macrophage modulation and cytokine suppression.
- Metabolic/endocrine (glucose and lipid metabolism): Alpha-glucosidase inhibition, insulin sensitization, lipid-lowering effects demonstrated in preclinical models.
- Cardiovascular system: Anticoagulant and hypolipidemic activities in preclinical settings.
- Nervous system: Neuroprotective effects in cell and animal models, particularly via fucoxanthin and polysaccharide fractions.
- Integumentary system (skin): Antioxidant, MMP-inhibitory, and anti-inflammatory properties relevant to dermocosmetic applications.
- Gastrointestinal system: Prebiotic potential of alginates and fucoidan, and microbiota-modulating effects in animal models.
- Oncological (experimental): Preclinical anticancer activities across multiple cancer cell types.
The wide range of recognized pharmacological properties of Sargassum spp. extracts or isolated pure components include anticancer, antibacterial, antifungal, antiviral, anti-inflammatory, anticoagulant, antioxidant, hypoglycaemic, hypolipidemic, antimelanogenic, anti-bone loss, hepatoprotective, and neuroprotective activities, suggesting that Sargassum is a rich source of health-maintaining and promoting agents.
8. Dosage Forms and Reported Dosages
The Chinese Pharmacopoeia recommends a dosage of 6–12 g of dried Sargassum for medicinal use. The standard decoction dose is 6–12 g; for treating goiter and thyroid nodules, the full dose of 10–12 g is commonly used, while for milder conditions such as edema or phlegm accumulation, lower doses of 6–9 g may suffice.
In preclinical studies, dosages reported in animal models include:
- S. hystrix extract administered orally to streptozotocin-induced diabetic rats at 200, 300, and 400 mg/kg once daily for 15 days.
- 100–300 mg/kg body weight of S. thunbergia extract significantly reduced body weight and fat accumulation in high-fat diet-induced obese mice, with reduced serum insulin, triglycerides, liver fats, and total cholesterol.
- Crude fucoidan from S. crassifolium at doses of 100, 200, and 400 mg/kg body weight in a dyslipidemic rat model.
- S. ilicifolium crude lipid extracts at 12.5–50 µg/mL significantly suppressed nitric oxide production in cell culture.
In in vitro studies, polysaccharides from S. naozhouense possessed strong antiviral activity against HSV-1 in vitro with an EC₅₀ of 8.92 μg/mL. Cell viability studies confirmed that S. horneri extract had no discernible toxicity at concentrations up to 100 μg/mL.
9. Safety Considerations and Interactions
9.1 Heavy Metal Accumulation: Arsenic
Sargassum species are known to present high contents of arsenic and inorganic arsenic, even in pristine waters, which can limit their use in food applications. S. fusiforme, traditionally consumed in Asia, has been the most thoroughly studied; some analyses describe total arsenic contents of 40–80 ppm in seaweed from China, Korea, and Japan, while other analyses found contents ranging from 70 to 150 ppm total arsenic (40–120 ppm inorganic) in Japanese hijiki imported into Spain. Some analyses have described total arsenic contents exceeding 200 ppm, mostly present in the most toxic inorganic form.
An expert assessment revealed that Sargassum seaweed has a high capacity for accumulating heavy metals — arsenic and cadmium in particular — which may pose a risk to human health and to the environment. Sargassum is reported to bioaccumulate heavy metals and metalloids, particularly arsenic; the concentration of arsenic in Sargassum that washed onto beaches in Mexico in 2018 ranged from 29.0–65.7 mg/kg, which is greater than recommendations for human consumption of seaweeds made by the French Agency for Food, Environmental and Occupational Health and Safety.
9.2 Heavy Metal Accumulation: Other Metals
Studies of dried seaweed products have indicated that levels of Cd, Ni, and Pb were relevant in some samples and may pose a risk to consumers; concentrations of Hg were overall the lowest found. Heavy metals have no beneficial function in the human body and are considered toxic even at low concentrations; exposure to heavy metals leads to negative gastrointestinal, neurotoxic, and carcinogenic effects, and it is widely known that marine organisms, especially seaweed, accumulate relevant amounts of arsenic.
9.3 Iodine Overload Risk
Modeling of increased seaweed consumption has shown that it could nearly double mean iodine intake in studied populations (to 300 μg/day in some scenarios) and increase average exposure to arsenic; intake of iodine was certainly higher in proportion to increased seaweed consumption. Some studies highlight that there are adverse effects to consuming large quantities of seaweed because it contains excessive heavy metals, arsenic, and iodine, and there are possible risks associated with consuming too much seaweed.
9.4 Interactions with Anticoagulant Medications
The anticoagulant properties of fucoidan from Sargassum species, demonstrated in preclinical settings, raise a theoretical concern for additive or synergistic effects when co-administered with anticoagulant or antiplatelet medications (such as warfarin, heparin, or antiplatelet agents). Sulfated polysaccharides from Sargassum fulvellum showed anticoagulant activity in preclinical models; whether this translates to clinically meaningful interactions in humans has not been formally evaluated in published trials.
9.5 Thyroid Drug Interactions
When using Hai Zao for its iodine content in thyroid disorders, it may temporarily suppress hyperthyroid symptoms but cannot treat the underlying condition long-term; in patients with hyperthyroidism, iodine-rich preparations of Hai Zao should generally be avoided. Iodine excess can worsen certain forms of thyroid disease, including autoimmune thyroiditis, and may interfere with thyroid medication dosing.
9.6 Compositional Variability
Particular attention must be paid to compositional variation between different harvest zones and years to ensure the economic viability and safety of any valorization project; spatial and inter-annual variability in the composition of stranded Sargassum has been documented. This variability — affecting polysaccharide content, iodine, heavy metals, and bioactive compounds — makes quality standardization a significant challenge for supplemental use.
9.7 Overall Safety Status
The numerous species, complex chemistry, and various pharmacological properties of Sargassum necessitate a systematic and critical assessment of future research direction and regulatory oversight. An evidence-based approach is needed to validate traditional uses and guide future research into potential new supplements and medicines derived from Sargassum. The principal, source-documented safety concerns are heavy metal (especially arsenic) bioaccumulation, iodine excess, and — at a theoretical level — interactions with anticoagulant therapies based on preclinical fucoidan data.
References
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