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Bdw2.5

Bladderwrack Research

Mostly mechanism / observationalLimited safety

5 peer-reviewed studies

What the evidence says

Mostly mechanism / observational

Most Bladderwrack studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.

Most evidence is from medium-quality randomised trials published 1999–2024 with a typical study size of 65 participants.

Based on 5 studies · 2 RCTs · 68 total participants

Confidence

Low confidence

By outcome

Glucose & metabolicProposed glycemic/metabolic support from fucoidan and polyphenols (only shown in combination products, not bladderwrack alone) · Unknown
Too few graded studies2 studies

Steady research

1 study in the last 5 years

199920112024

1RCT2024

In plain English: Similarly, no between-group differences were observed for the changes in the secondary outcomes.

Geurts KAM, Meijer S, Roeters van Lennep JE, Wang X, Özcan B, Voortman G, Liu H, Castro Cabezas M, Berk KA, Mulder MT. · Nutrients (2024)

Results The change in weekly average glucose levels was 8.2 ± 2.1 to 9.0 ± 0.7 mmol/L ( p = 0.2) in the S. fusiforme group (n = 12) and 10.1 ± 3.3 to 9.2 ± 0.7 mmol/L ( p = 0.9) in the F. vesiculosus group (n = 10).
The between-group difference was non-significant.
Similarly, no between-group differences were observed for the changes in the secondary outcomes.

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2RCTCited 18×n=65 · small study2019

In plain English: A nutraceutical combining Ascophyllum and Fucus polyphenols with chromium picolinate improved insulin sensitivity and glycemic status — but larger studies are required to confirm.

Derosa G, Cicero AFG, D'Angelo A, Maffioli P. · Phytother Res (2019)

Combination of Fucus + Ascophyllum polyphenols + chromium picolinate reduced HbA1c, fasting and postprandial glucose, and HOMA-IR vs placebo
Effect cannot be attributed to bladderwrack alone — it was a multi-ingredient product including chromium
Authors explicitly state larger randomized studies are needed

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3ObservationalCited 42×1999

In plain English: Regular consumption of algae, especially Laminaria species, could result in iodine levels sufficient to cause thyroid problems; Fucus was among the seaweeds analyzed.

Phaneuf D, Côté I, Dumas P, Ferron LA, LeBlanc A. · Environ Res (1999)

Analyzed Fucus vesiculosus and other seaweeds for metals (including arsenic, cadmium, lead) and iodine
Iodine-thyroid risk was flagged primarily for high-iodine Laminaria species; Fucus vesiculosus was among the seaweeds analyzed for contaminants
Recommends choosing low-iodine species for frequent consumption

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4AnimalCited 4×2011

In plain English: Fucoidan from Fucus showed antithrombin and anti-factor Xa activity, with both antithrombotic and hemorrhagic (bleeding) activity increasing with dose.

Drozd NN, Miftakhova NT, Savchik EIu, et al. · Eksp Klin Farmakol (2011)

Fucoidan from a Fucus species had measurable antithrombin and anti-factor Xa activity
Both antithrombotic and hemorrhagic activity rose with dose in rats
Mechanistic basis for a plausible bleeding-risk interaction in humans

5Case StudyCited 29×n=3 · very small study2004

In plain English: These pilot data suggest dietary bladderwrack may prolong menstrual cycle length and exert anti-estrogenic effects, but well-controlled clinical trials are needed to confirm.

Skibola CF. · BMC Complement Altern Med (2004)

Only three pre-menopausal women — a case report, not a controlled trial
Associated with longer menstrual cycles and, in one woman, lower estradiol and higher progesterone
Hypothesis-generating only; author calls explicitly for controlled trials

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Bladderwrack Research

Mostly mechanism / observational

The Effect of Sargassum fusiforme and Fucus vesiculosus on Continuous Glucose Levels in Overweight Patients with Type 2 Diabetes Mellitus: A Feasibility Randomized, Double-Blind, Placebo-Controlled Trial

Ascophyllum nodosum and Fucus vesiculosus on glycemic status and on endothelial damage markers in dysglicemic patients.

Evaluation of the contamination of marine algae (seaweed) from the St. Lawrence River and likely to be consumed by humans.

[Antithrombotic and hemorrhagic activities of fucoidan isolated from Fucus evanescens brown algae].

The effect of Fucus vesiculosus, an edible brown seaweed, upon menstrual cycle length and hormonal status in three pre-menopausal women: a case report.