Kelp
Research reviewed: 2003–2018
Kelp (Laminaria species) is a dietary supplement with 8 published peer-reviewed studies involving 724 participants, researched for Thyroid Support & Iodine, Antioxidant Effects, Weight Management and 1 more areas.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Thyroid Support & Iodine
ModerateAntioxidant Effects
ModerateWeight Management
ModerateThyroid Function & Metabolic Health
ModerateResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Thyroid Support & Iodine
Evaluate kelp supplementation on thyroid function and iodine status
Study Type
Randomised Controlled Trial
Purpose
Evaluate kelp supplementation on thyroid function and iodine status
Dose
600 mg/day kelp (250 µg iodine)
Participants
120
Duration
12 weeks
Results
Urinary iodine excretion significantly increased; TSH normalised in iodine-deficient subjects; thyroid function improved
How They Measured It
TSH, T3, T4, urinary iodine excretion
Assess kelp iodine supplementation on thyroid hormone levels
Study Type
Randomised Controlled Trial
Purpose
Assess kelp iodine supplementation on thyroid hormone levels
Dose
Kelp 600–3000 µg iodine equivalent
Participants
80
Duration
8 weeks
Results
Iodine status improved; TSH normalised in hypothyroid subjects; caution: excessive doses may cause transient hyperthyroidism
How They Measured It
TSH, free T3, free T4, thyroid antibodies
Antioxidant Effects
Evaluate kelp antioxidant properties including fucoidan fraction
Study Type
Randomised Controlled Trial
Purpose
Evaluate kelp antioxidant properties including fucoidan fraction
Dose
Kelp extract 2 g/day
Participants
60
Duration
8 weeks
Results
Significant improvement in ORAC and FRAP; reduced MDA levels; antioxidant capacity elevated vs placebo
How They Measured It
ORAC, FRAP antioxidant capacity, MDA, oxidative stress
Review kelp bioactive antioxidant compounds and clinical evidence
Study Type
Systematic Review
Purpose
Review kelp bioactive antioxidant compounds and clinical evidence
Dose
Various
Participants
150
Duration
Various
Results
Multiple bioactive antioxidants in kelp including fucoidan, phlorotannins, fucoxanthin; clinical evidence confirms antioxidant activity
How They Measured It
Narrative review of polyphenol, fucoidan, carotenoid content and clinical data
Weight Management
Assess kelp extract on body weight and thyroid-metabolic axis
Study Type
Randomised Controlled Trial
Purpose
Assess kelp extract on body weight and thyroid-metabolic axis
Dose
Kelp extract 4 g/day
Participants
78
Duration
12 weeks
Results
Modest reduction in body weight (−1.2 kg); RMR increased by 3.5%; thyroid-mediated metabolic enhancement proposed
How They Measured It
Body weight, BMI, RMR, thyroid hormones
Evaluate kelp extract on cholesterol and cardiovascular markers
Study Type
Randomised Controlled Trial
Purpose
Evaluate kelp extract on cholesterol and cardiovascular markers
Dose
Kelp extract 2 g/day
Participants
68
Duration
12 weeks
Results
LDL reduced by 8%; CRP reduced by 10%; blood pressure modestly reduced; fucoidan and fibre contribute
How They Measured It
LDL, HDL, total cholesterol, CRP, blood pressure
Thyroid Function & Metabolic Health
Test kelp supplementation on thyroid function in healthy adults
Study Type
Randomised Controlled Trial
Purpose
Test kelp supplementation on thyroid function in healthy adults
Dose
Kelp tablets 300 µg iodine/day
Participants
80
Duration
8 weeks
Results
TSH slightly reduced in euthyroid subjects; T3 elevated; metabolic rate improvement trend; caution for hyperthyroid risk
How They Measured It
TSH, T3, T4, metabolic rate
Assess kelp on cardiovascular and antioxidant markers in obese adults
Study Type
Randomised Controlled Trial
Purpose
Assess kelp on cardiovascular and antioxidant markers in obese adults
Dose
Kelp extract 5 g/day
Participants
88
Duration
16 weeks
Results
Significant cardiovascular risk marker improvements; antioxidant capacity enhanced; modest weight reduction; well-tolerated
How They Measured It
CRP, lipids, oxidative stress, body weight
Frequently Asked Questions
Common questions about Kelp research
There are currently 8 peer-reviewed studies on Kelp (Laminaria species), involving 724 total participants. Research covers Thyroid Support, Iodine, Antioxidant and 1 more areas. The overall evidence strength is rated as Strong.
The evidence is currently rated as "Strong Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (8 human studies), and reported outcomes.
Kelp has been researched for: Thyroid Support, Iodine, Antioxidant, Weight Management. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 8 out of 8 studies are human trials. Human trials carry more weight in our evidence scoring system.
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