Benefits
Prostate health and urinary symptom scores in men
In a 90-day placebo-controlled trial in 95 men aged 45 to 80 with moderate prostate enlargement, 1 g a day of a Marinova Undaria extract (85.5% fucoidan) lowered a urinary symptom score by 3.40 points versus 0.93 on placebo. Urine flow, leftover urine and PSA did not differ. Marinova funded the trial, and two authors worked for it. Urinary symptoms need a medical check first.
Joint comfort and stiffness
In an open-label pilot in 12 adults with knee osteoarthritis, a three-seaweed Maritech blend with vitamin B6, zinc and manganese lowered a symptom score more at 1,000 mg than at 100 mg a day, with no placebo group. In a later placebo-controlled trial in 122 adults, 300 mg a day of a Marinova Fucus extract for 12 weeks did no better than placebo.
Blood sugar and insulin markers
In a placebo-controlled trial in 72 adults with obesity, 500 mg twice daily of Maritech Synergy for 90 days did not change insulin resistance, HbA1c, lipids, weight or blood pressure. In a crossover trial in 38 healthy adults, single 500 mg or 2 g doses taken before white bread did not lower the blood sugar or insulin rise compared with placebo.
Immune and inflammatory markers in active adults
In placebo-controlled crossover trials, 1 g a day of Marinova fucoidan left most blood immune markers unchanged after sprint exercise, while interleukin-6 and interleukin-10 were higher 30 minutes after exercise. In 12 men in hard training, salivary IgA rose more after exercise on fucoidan. Uncontrolled studies reported shifts in immune cells and fecal lysozyme. All are lab markers, not infections.
Strength and power during resistance training
In 20 adults doing 6 weeks of resistance training, 1 g a day of a Marinova Undaria and Fucus blend gave the same squat strength gain as placebo. Peak power rose only within the fucoidan group, with no significant group difference. In a sprint exercise trial and a 3-week training trial, performance did not differ from placebo.
Body fat percentage during resistance training
In 20 adults doing 6 weeks of resistance training, body fat percentage fell more with 1 g a day of a Marinova Undaria and Fucus blend than with placebo (interaction p = 0.03), while total body mass and lean mass did not differ between groups. In 72 adults with obesity, 1 g a day of Maritech Synergy for 90 days did not change weight or waist size.
Mechanism of action
Water extraction keeps fucoidan with seaweed polyphenols
Marinova suspends dried, milled seaweed in slightly acidic water, filters out solids and salts, and dries the filtrate. The resulting extracts carry fucoidan together with alginate, mannitol and seaweed polyphenols. Composition differs by species and grade, which is why results from one Maritech extract do not automatically apply to another.
Little is absorbed from the gut
Fucoidan is a large polysaccharide. In its FDA notice, Marinova described a human study showing that less than 1% of swallowed fucoidan reaches the blood, and an oral clotting pilot found effects far weaker than in the test tube. Any effects may therefore begin mostly in the gut.
Immune cell signaling (lab and animal work)
In cell and animal studies, fucoidan alters cytokine release and the activity of macrophages, natural killer cells and other immune cells. These are proposed explanations for the small immune marker changes in people, not mechanisms confirmed in human trials of Maritech extracts.
Clinical trials
Randomized, double-blind, placebo-controlled trial of 1 g/day Undaria pinnatifida fucoidan (85.5% fucoidan, two capsules daily) made and supplied by Marinova, which funded the trial; two authors were Marinova employees when it was planned and run (Wimmer et al. 2026, Res Rep Urol).
95 men aged 45 to 80 in India with moderate benign prostatic hyperplasia (symptom score 8 to 19), as the study population.
The International Prostate Symptom Score fell 3.40 points with fucoidan versus 0.93 with placebo by day 90 (p = 0.0015), with better voiding, storage and quality-of-life scores. Urinary flow rate, residual urine volume and PSA did not differ between groups. Adverse events: 12 on fucoidan, 10 on placebo. A single sponsor-funded trial.
Double-blind, randomized, placebo-controlled trial of 300 mg/day of a Marinova Fucus vesiculosus extract (85% fucoidan in the abstract) for 12 weeks, sponsored by Marinova, whose employee J. H. Fitton co-authored it (Myers et al. 2016, Biologics).
122 adults with mild-to-moderate hip or knee osteoarthritis as the study population; 96 completed.
Symptom reduction on the Comprehensive Osteoarthritis Test did not differ from placebo; both groups improved. Adverse events did not differ in frequency, and blood safety tests showed no clinically meaningful changes.
Single-site, double-blind, placebo-controlled trial of 500 mg fucoidan twice daily for 90 days; the registry names the product Maritech Synergy, the trial was funded by Marinova, and two authors (Fitton, Stringer) were from Marinova. Body weight and waist size also did not differ from placebo. (Wright et al. 2019, J Altern Complement Med).
72 obese adults aged 18 to 65 without diabetes in Hobart, Tasmania (35 fucoidan, 37 placebo).
No difference from placebo in the primary outcome, insulin resistance (mean HOMA change 0 on placebo and -0.1 on fucoidan, p = 0.73), or in HbA1c, lipids or blood pressure.
Double-blind, placebo-controlled, randomized crossover trial of single 500 mg and 2,000 mg doses of Maritech Synergy (Fucus vesiculosus extract, 28% polyphenols and 67% fucoidan) taken 30 minutes before 50 g of carbohydrate from white bread; supported in part by Marinova (Murray et al. 2018, Nutrients).
38 healthy adults aged 19 to 56 (26 non-Asian, 12 Asian).
Neither dose lowered the blood glucose or insulin response over 2 hours compared with placebo.
Randomized, double-blind, placebo-controlled, counterbalanced crossover of 1 g/day Undaria pinnatifida fucoidan in 500 mg capsules produced by Marinova, for 2 weeks per period; funded by Marinova (McFadden et al. 2023, J Int Soc Sports Nutr).
16 recreationally active adults (8 men, 8 women).
Exercise performance and most blood immune markers did not differ by condition. Interleukin-6 and interleukin-10 were higher 30 minutes after exercise on fucoidan. No adverse events were reported.
Double-blind, placebo-controlled crossover of 1 g/day fucoidan for 3 weeks per period; the paper describes an Undaria pinnatifida extract with over 85% fucoidan, while the registry entry lists Marinova as funder and supplier of an Undaria and Fucus extract with 75.5% fucoidan (Cox et al. 2023, J Sports Sci).
12 healthy, recreationally active men.
Training gains in mean power did not differ between supplements. Fecal and resting salivary markers were largely stable; the salivary IgA response to acute exercise was greater on fucoidan (p = 0.02), and other between-group differences were small.
Double-blind, placebo-controlled parallel trial of 1 g/day of a Marinova Undaria pinnatifida and Fucus vesiculosus blend (81.5% fucoidan, 11.2% polyphenols) versus microcrystalline cellulose during supervised resistance training; supported by Marinova (Cousins et al. 2025, Sci Rep).
20 apparently healthy adults (9 men, 11 women), 10 per group.
Squat strength rose in both groups with no treatment effect (p = 0.48). Peak power rose only within the fucoidan group; the group by training interaction was not significant (p = 0.08). Body fat percentage showed a significant interaction (p = 0.03) favoring fucoidan, while lean mass and total mass did not differ.
Open-label combined phase I and II pilot of a Maritech blend (Fucus vesiculosus 85%, Macrocystis pyrifera 10%, Laminaria japonica 5%) plus vitamin B6, zinc and manganese at 100 mg or 1,000 mg/day for 12 weeks; sponsored by Marinova, whose employee J. H. Fitton co-authored it (Myers et al. 2010, Biologics).
12 adults with knee osteoarthritis as the study population (5 on 100 mg, 7 on 1,000 mg).
The average arthritis symptom score fell 18% on 100 mg and 52% on 1,000 mg, a dose-related change with no placebo group. A later placebo-controlled trial of a Marinova Fucus extract at 300 mg/day found no benefit.