Nori and blood pressure in young Japanese children
What it found
In a 10-week trial in 4 to 5 year old Japanese children, eating 1.76 grams of nori a day lowered diastolic blood pressure in boys but made no difference in girls.
The authors say seaweed may help prevent high blood pressure in childhood.
What they found
Studies in people
Diastolic blood pressure in boys
In boys, diastolic blood pressure fell by 6.77 mm Hg in the nori group and by 0.05 mm Hg in the control group. The authors say this difference was significant.
Systolic blood pressure in boys
Systolic blood pressure fell by 8.29 mm Hg in the nori group and rose by 0.50 mm Hg in the control group. The authors report this difference was borderline significant.
No effect in girls
In girls, there was no difference in blood pressure changes between the nori and control groups.
Energy intake
Boys in the nori group ate 111.3 kcal per day less by the end of the study, while the control group did not change. Adjusting for this did not change the blood pressure result.
Other findings
Possible active components
The authors note that nori contains peptides that may block ACE I, plus fiber, minerals, vitamins, folic acid and eicosapentaenoic acids. They could not identify which factor caused the blood pressure change.
What the authors conclude
“Nori intake lowered DBP level in boys.”
Also in their conclusions
- They conclude that nori intake lowered diastolic blood pressure in boys aged 4 to 5 years.
- They say that seaweed intake might have preventive effects on elevated blood pressure in childhood.
- They advise that future prospective research is needed to determine the preventive effects of seaweed intake early in life on hypertension in later adulthood.
How it was done
Blood pressure tracks from childhood into adulthood, and the authors wanted to see whether a common food could help lower it early. They had previously found a link between seaweed intake and lower blood pressure in a study of Japanese children.
They studied 89 children aged 4 to 5 at a preschool in Aichi Prefecture, Japan, in 2010. Two classes were assigned to eat 1.76 grams of roasted nori each day with school lunch for 10 weeks, and one class ate their usual diet. Blood pressure was measured three times before and at the end of the study.
What it can’t tell you
- The trial was unblinded and assigned whole classes rather than individual children, so some differences between groups existed at the start.
- The authors could not guarantee that children ate the nori on weekends.
- The study lasted only 10 weeks, so it cannot show whether the blood pressure change lasts or prevents later hypertension.
The paper
- Title
- Effect of Dietary Nori (Dried Laver) on Blood Pressure in Young Japanese Children: An Intervention Study
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Wada K, Tsuji M, Nakamura K, et al (2021). Effect of Dietary Nori (Dried Laver) on Blood Pressure in Young Japanese Children: An Intervention Study. Journal of epidemiology. doi:10.2188/jea.JE20190176Free full textPubMed 32201400DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error