Supplement
Fucoidan
Glycemic and inflammatory markers in prediabetes, and antibody response to influenza vaccine in older adults; small trials of different seaweed extracts on surrogate endpoints A lab value or measurement used in place of the outcome that matters, such as LDL cholesterol standing in for heart attacks. Moving a surrogate does not always move the outcome..
Grade C: human trials exist, but they are small, mixed or not yet repeated. This is not a finding that it does not work. How to read a grade →
Fucoidan is a sugar compound from brown seaweed. Small studies looked at blood sugar and swelling markers in prediabetes. They also looked at the body's response to the flu shot in older adults. Each study used a different seaweed extract. These are blood tests, and no study shows fewer illnesses or better health.
- Dose studied
- 1,000 mg/day
- Form graded
- Standardized brown-seaweed fucoidan
- Cited PMIDs PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed.
- PMID 39645105 →
A letter describes the human evidence, not the product, the manufacturer, or the ingredient's worth.
See the full evidence record →Who responds: this record's trial reading reports no subgroup that identifies who responds.
Funding: All three trials this Grade C rests on were funded by industry or funders the reports do not identify: Liu 2025 (PMID 39645105) by a funder the indexed report does not name; Negishi 2013 (PMID 24005608) by a funder the indexed report does not name; Wright 2019 (PMID 30312135) by the maker of the product it tested. The funder's role in design and analysis is not stated here, because the full trial reports could not be read. The letter is what the trials support under the grading rules; the funding is stated here so it can be weighed alongside it.
Fucoidan for glycolipid and immune measures, graded on published human trial evidence.
How this letter has changed · latest: October 2026 · Corrected
The record said Liu 2025 (PMID 39645105) showed lipid and glucose effects; its abstract reports a smaller rise in glycated serum protein and lower inflammatory markers with no lipid result, and the ref now says so. Added: Wright 2019 (PMID 30312135), a maker-funded placebo-controlled trial null on insulin resistance, lipids, HbA1c A blood test that reflects average blood sugar over the previous two to three months. and glucose at 1 g/day for 90 days; Hernández-Corona 2014 (PMID 24611906), where HOMA insulin resistance rose on fucoidan; Negishi 2013 (PMID 24005608), the influenza-vaccine antibody trial that carries the immune half of the best-use line. The record now states that fucoidan products differ by seaweed source and molecular weight, so trials of different extracts do not replicate each other. Letter unchanged.PMID 39645105 PMID 30312135 PMID 24611906 PMID 24005608
Every change to a letter on this site is dated and published. The full evidence log →
Commercial disclosure
EBL earns no commission on any supplement it grades. A purchase made through the dispensary link below pays EBL nothing, the practitioner discount goes to you in full. The dispensary is Fullscript, a practitioner dispensary, and many of the professional-grade brands in it are sold mainly through practitioners rather than in health food stores. Grades are assigned by published rubric before any commercial relationship exists and are never influenced by one. Full disclosure.
No dose is published here. This record carries no authored dose, because the cited trials do not converge on a single figure. Each trial cited on this page states the dose it used, and EBL has not turned those into a recommendation.
Standardized extracts/forms were used in the cited trials; product quality varies.
The cited trial gave 1,000 mg a day (PMID 39645105). Its summary does not state a time of day or whether it was taken with food.
Checked against the published summary; the full paper could not be read. What the cited trials did, not a schedule. Every supplement, by trial timing →
Raised bleeding risk. Iodine content varies by seaweed source and can matter in thyroid disease. Separation from surgery is the usual clinical margin.
Anticoagulants and antiplatelets. Fucoidan is a sulphated polysaccharide with heparin-like activity, and a small clinical study measured a measurable anticoagulant effect in people rather than only in vitro.
Fucoidan has measurable anticoagulant activity in people. A small clinical study measured anticoagulant activity from oral fucoidan in humans, which puts this caution above the purely mechanistic ones on this page. Irhimeh et al. (Blood Coagulation and Fibrinolysis, 2009; PMID 19696660): pilot clinical study evaluating the anticoagulant activity of fucoidan.
Immune markers (NK cell activity, inflammatory cytokines) at baseline and 8 weeks if available. For metabolic applications, monitor fasting glucose and lipid panel at baseline and 12 weeks. Fucoidan molecular weight and source species vary significantly across products: Species and standardization before comparing to trial data.
Primary evidenceFour papers, each linked to its PubMed record.
Liu et al. (Int J Biol Macromol, 2025; PMID 39645105): randomized placebo-controlled trial, 70 Chinese adults with prediabetes, 1,000 mg/day for 12 weeks; a smaller rise in glycated serum protein and lower TNF-alpha, IL-6 and LPS than placebo An inactive substitute made to look like the real treatment, so participants cannot tell which one they received.; no lipid result is reported, so this trial does not support a lipid claim; funding not stated in the indexed record. Negishi et al. (J Nutr, 2013; PMID 24005608): randomized placebo-controlled trial, 70 Japanese adults over 60, 300 mg/day of a mekabu fucoidan for 4 weeks before influenza vaccination; higher antibody titers against all three vaccine strains than placebo; authors declare no conflicts. Against: Wright et al. (J Altern Complement Med, 2019; PMID 30312135): randomized placebo-controlled trial, 72 obese non-diabetic adults, 500 mg twice daily for 90 days, funded by the extract's maker; no difference from placebo in insulin resistance, lipids, HbA1c, fasting glucose or any other measured parameter. Hernández-Corona et al. (J Med Food, 2014; PMID 24611906): 25 overweight or obese adults, 500 mg/day for 3 months; diastolic pressure and LDL Low-density lipoprotein cholesterol, the cholesterol fraction most closely tied to plaque in the arteries. fell, but insulin, HOMA beta-cell and HOMA insulin resistance ROSE on fucoidan. Fucoidan preparations differ by seaweed source and molecular weight, so trials of different extracts do not replicate one another. Grade C: small trials of different extracts on surrogate endpoints The outcome a trial measures to decide whether the treatment worked, such as heart attacks, blood pressure or a symptom score., with a null and an adverse-direction result beside the positive ones.
Educational use only · Not medical advice · Starting, stopping or changing any supplement or medication is a decision for your physician
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. The grade on this page describes the strength of published human trial evidence in the populations studied. It is not a recommendation for any individual and is not medical advice. Starting, stopping or changing any supplement or medication is a decision for your physician.
This page carries a letter. EBL takes no commission, referral fee or payment of any kind on anything it grades. No letter has been bought and none is for sale.
How this is enforced
That is not a promise, it is a build condition. Two checks run on every deploy: one refuses to publish if a commission is claimed on anything graded, the other refuses if a page names a commercial relationship that is not declared in the register. If either fails, this page does not go live. You can read how the checks work, and what they do not cover, on the evidence integrity page.
How EBL searched for the trials (1 search)
The search that was run, what it returned, and what was left out and why, so the absence of evidence can be checked as well as its presence.
fucoidan[tiab] AND (randomized controlled trial[pt] OR meta-analysis[pt]) AND humans[mesh]Grades move when new trials publish. A free monthly email lists every grade EBL moved, with the reason and the trial behind it: the sign-up is on the Evidence Log →