Dried laver and gut bacteria in older women
What it found
In 24 older women, eating 4 g of dried laver every day for 12 weeks was linked to changes in gut bacteria, including a rise in bacterial variety.
The study was small and had no placebo group.
What they found
Studies in people
Bacterial variety rose
Bacterial richness and evenness both increased from the start to the end of the 12 weeks in the metabolic syndrome group and in the control group. There was no significant difference between the two groups at either time point.
Firmicutes to Bacteroidetes ratio
The ratio of Firmicutes to Bacteroidetes bacteria fell by 0.81-fold in the control group and 0.54-fold in the metabolic syndrome group. The fall was proportionally larger in the metabolic syndrome group.
Community structure changed
A presence-and-absence measure of bacterial community structure showed significant differences between the start and end of the study within both groups. Other measures of community structure did not show significant differences.
Four bacterial groups changed
One bacterial group, CAG_873, increased more in the control group. Three others, Muribaculaceae, Paraprevotella and Tyzzerella, were enriched in the metabolic syndrome group after the 12 weeks.
Tyzzerella rose unexpectedly
Tyzzerella, which has been linked to cardiovascular disease risk and obesity in other studies, increased in both groups after laver intake. The authors say the meaning of this rise cannot be established from this study.
What the authors conclude
“Given the limited sample size and pilot design, these findings should be regarded as preliminary and hypothesis-generating.”
Also in their conclusions
- They say the findings are preliminary and hypothesis-generating because of the small sample size and pilot design.
- They say the potentially greater microbiome responsiveness in the metabolic syndrome group justifies further investigation of dried laver in people with pre-existing gut dysbiosis.
- They call for adequately powered, randomized, placebo-controlled trials with metabolic biomarker assessment before dried laver can be considered as a gut-microbiome-targeted nutritional strategy for metabolic syndrome in older women.
How it was done
The authors wanted to test whether laver, a seaweed rich in fibre that gut bacteria can ferment, could shift the gut microbiome in older women, especially those with metabolic syndrome. Human data on seaweed-based gut microbiome interventions were lacking.
They recruited 24 women aged 50 and over, 13 with metabolic syndrome and 11 without, and gave them 4 g of dried laver (Porphyra tenera) daily for 12 weeks. Stool samples were collected before and after, and the bacteria present were analysed by gene sequencing.
What it can’t tell you
- There was no placebo group, so the changes seen cannot be attributed solely to laver.
- The study did not measure blood markers such as waist circumference, blood pressure or blood glucose, so it cannot show whether the bacterial changes affected metabolic health.
- The participants were all older Korean women, so the results may not apply to other groups.
Who paid
- Funding
- Funded by Ministry of Oceans and Fisheries; National Research Foundation of Korea (from the PubMed record).
- Conflicts
- The authors declare no conflicts of interest.
- Authors work at
- Ewha Womans University, Republic of Korea; Inha University, Republic of Korea; Dongjak-gu Public Health Center, Republic of Korea
The paper
- Title
- Dietary Dried Laver (Porphyra tenera) Modulates Gut Microbiota Composition and Diversity in Older Women with and Without Metabolic Syndrome: An Exploratory Pilot Study
- Type
- Study
- Evidence
- Studies in people
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Shin D, Lee S, So B, Kang C, Lee KJ (2026). Dietary Dried Laver (Porphyra tenera) Modulates Gut Microbiota Composition and Diversity in Older Women with and Without Metabolic Syndrome: An Exploratory Pilot Study. Nutrients. doi:10.3390/nu18101535Free full textPubMed 42196995DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error