Supplement

Brown Seaweed Extract

Brown seaweed extract is a concentrate of compounds from brown algae, such as fucoidan and phlorotannins, which are thought to influence digestion and inflammation. In people with fatty liver disease, small studies found blood pressure improved and C-reactive protein, a marker of inflammation, went down, though the evidence is limited. Studies on appetite in obesity and on blood glucose found no clear difference, and that evidence is very limited.

Updated 30 September 2026
How we grade
1 study cited

Best evidence: Grade C
Conditions studied: 6
Outcomes: 24
Graded outcomes: 0042

Evidence by condition

Strong
Moderate
Limited
Very limited

6 conditions

Nonalcoholic Fatty Liver Disease (NAFLD)

Nonalcoholic Fatty Liver Disease (NAFLD): outcomes studied for Brown Seaweed Extract
Grade	Outcome	Effect	Size	Studies	People
	Blood Pressure Small Improvement	Improves (the measure goes down)	Small effect		151 people
	C-Reactive Protein (CRP) Small Decrease	Improves (the measure goes down)	Small effect		151 people
	Liver Enzymes Improvement	Improves (the measure goes down)		1 study	151 people
Studies that measured liver enzymes The effects of Xanthigen in the weight management of obese premenopausal women with non-alcoholic fatty liver disease and normal liver fatDiabetes Obes Metab · PMID 19840063
	Liver Fat Improvement	Improves (the measure goes down)			151 people
	Metabolic Rate	Improves (the measure goes up)			151 people
	Triglycerides	Changes; see studies			151 people
	Weight	Changes; see studies			151 people

General Liver Health

General Liver Health: outcomes studied for Brown Seaweed Extract
Grade	Outcome	Effect	Size	Studies	People
	C-Reactive Protein (CRP) Small Decrease	Improves (the measure goes down)	Small effect		151 people
	Liver Enzymes	Changes; see studies		1 study	151 people
Studies that measured liver enzymes The effects of Xanthigen in the weight management of obese premenopausal women with non-alcoholic fatty liver disease and normal liver fatDiabetes Obes Metab · PMID 19840063
	Liver Fat	Changes; see studies			151 people
	Metabolic Rate	Improves (the measure goes up)			151 people
	Triglycerides	Changes; see studies			151 people
	Weight	Changes; see studies			151 people

Weight Loss & Maintenance

Blood Pressure: improves
Liver Enzymes: changes; see studies
C-Reactive Protein (CRP): changes; see studies

Weight Loss & Maintenance: outcomes studied for Brown Seaweed Extract
Grade	Outcome	Effect	Size	Studies	People
	Blood Pressure Small Improvement	Improves (the measure goes down)	Small effect		151 people
	Liver Enzymes	Changes; see studies		1 study	151 people
Studies that measured liver enzymes The effects of Xanthigen in the weight management of obese premenopausal women with non-alcoholic fatty liver disease and normal liver fatDiabetes Obes Metab · PMID 19840063
	C-Reactive Protein (CRP)	Changes; see studies			151 people
	Liver Fat	Changes; see studies			151 people
	Metabolic Rate	Improves (the measure goes up)			151 people
	Triglycerides	Changes; see studies			151 people
	Weight	Changes; see studies			151 people

Obesity

Appetite
Food Intake: changes; see studies

Obesity: outcomes studied for Brown Seaweed Extract
Grade	Outcome	Effect	Size	Studies	People
	Appetite No effect		NoneNo effect		79 people
	Food Intake	Changes; see studies		1 study	79 people
Studies that measured food intake Ascophyllum nodosum enriched bread reduces subsequent energy intake with no effect on post-prandial glucose and cholesterol in healthy, overweight males. A pilot studyAppetite · PMID 22100188

Metabolic Health

Blood glucose

Metabolic Health: outcomes studied for Brown Seaweed Extract
Grade	Outcome	Effect	Size	Studies	People	Studies list
	Blood glucose No effect		NoneNo effect		23 people

Skin Health

Skin Quality: improves

Skin Health: outcomes studied for Brown Seaweed Extract
Grade	Outcome	Effect	Size	Studies	People	Studies list
	Skin Quality	Improves (the measure goes up)		1 study	10 people
Studies that measured skin quality Treatment of human skin with an extract of Fucus vesiculosus changes its thickness and mechanical propertiesJ Cosmet Sci · PMID 11917251

Key findings

Blood PressureNonalcoholic Fatty Liver Disease (NAFLD)Improves (the measure goes down)
C-Reactive Protein (CRP)Nonalcoholic Fatty Liver Disease (NAFLD)Improves (the measure goes down)
AppetiteObesity

Shop Brown Seaweed Extract

Third-party tested Brown Seaweed Extract products. The evidence above is limited, so read it before you buy.

Grade C

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Studies cited

1 study from PubMed

A randomised crossover placebo-controlled trial investigating the effect of brown seaweed (Ascophyllum nodosum and Fucus vesiculosus) on postchallenge plasma glucose and insulin levels in men and womenAppl Physiol Nutr Metab · PMID 22087795