Miso soup and nighttime blood pressure in people
What it found
In 38 people with high-normal blood pressure or stage I hypertension, miso soup taken twice daily for 8 weeks lowered nighttime blood pressure but did not change daytime blood pressure.
The authors say this is the first report showing miso reduces nighttime blood pressure in humans.
What they found
Studies in people
Daytime blood pressure
Miso soup did not change daytime blood pressure compared with the soy food, even though the miso group ate much more salt. The authors note that a daily miso soup with 3.8 g salt would be expected to raise systolic blood pressure by 6.46 mmHg, but that did not happen here.
Nighttime blood pressure
After 8 weeks, nighttime systolic and diastolic blood pressure during the whole night were significantly lower in the miso group than in the soy food group. The miso group also had lower nighttime blood pressure than at the start of the study, while the soy food group did not.
Nighttime pulse rate
Miso soup did not affect nighttime pulse rate. There were no differences in pulse rate between the miso and soy food groups at any time point.
Stage I hypertension subgroup
In the subgroup with stage I hypertension, nighttime blood pressure during the whole night was significantly lower in the miso group than in the soy food group. Nighttime diastolic blood pressure at 0200 and 0400 hours was 9.4% and 8.0% lower in the miso group, but these differences were not statistically significant.
Body weight and fluid
Body weight decreased slightly in the miso group compared with the soy food group. The authors suggest this may be due to a reduction in body fluid levels, which could explain the lower nighttime blood pressure.
Blood fats and glucose
Miso intake did not influence lipid or glucose metabolism overall, but it did significantly increase LDL cholesterol levels. The authors say the nutrients in the miso combination were not enough to improve glucose or lipid metabolism in people without these abnormalities.
What the authors conclude
“This is the first report to show that long-term awase miso intake decreases BP in humans.”
Also in their conclusions
- They conclude that long-term awase miso intake does not influence daytime blood pressure despite its relatively high salt concentration (3.8 g in two servings).
- They state that it does, however, significantly reduce nighttime blood pressure, perhaps by promoting diuresis.
- They say this is the first report to show that long-term awase miso intake decreases blood pressure in humans.
How it was done
Common miso soup is often thought to raise blood pressure because of its salt, but some studies suggest it may not. The authors wanted to test whether a mix of two miso types, one with natriuretic effects and one with ACE inhibitory effects, would lower blood pressure in people.
They randomly assigned 40 people aged 40 to 69 with high-normal blood pressure or stage I hypertension to eat either miso soup (32 g of a 2:1 mix of Nenrin and MK-34-1 miso, providing 3.8 g salt per day) or a soy food control (14.4 g soy food with 0.2 g salt per day) twice daily for 8 weeks. Daytime blood pressure was measured in the clinic, and nighttime blood pressure was measured at home with an automatic monitor. Two people dropped out, leaving 38 for analysis.
What it can’t tell you
- This trial was small (38 people) and lasted only 8 weeks, so it cannot show what happens over longer periods or in larger groups.
- The study did not measure ACE activity or body fluid spaces directly, so the exact reason for the nighttime blood pressure drop is not known.
- The results apply to people with high-normal blood pressure or stage I hypertension, not to everyone.
Who paid
- Conflicts
- The Marukome Nenrin and Marukome MK-34-1 combination miso was originally manufactured and offered by Marukome Co., Ltd., Nagano. The study was designed by TTC, Co., Ltd., Tokyo and performed by Meiseikai Higashi Shinjuku Clinic, Tokyo, Japan under the supervision of Yoshio Uehara. Manabu Kitagawa, Minami Yamada, and Seiki Itou were responsible for supplying the test miso. They were not involved in the execution of the clinical study, data analysis or writing the article. Tetsuro Yamamoto was responsible for controlling the study. The collected data were analyzed by Hiroe Sakuyama Tomari and Shoko Yamakawa. The article was independently written by Yoshio Uehara.
- Authors work at
- Kyoritsu Women's University, Japan
The paper
- Title
- Long-term intake of miso soup decreases nighttime blood pressure in subjects with high-normal blood pressure or stage I hypertension
- 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
- Kondo H, Sakuyama Tomari H, Yamakawa S, et al (2019). Long-term intake of miso soup decreases nighttime blood pressure in subjects with high-normal blood pressure or stage I hypertension. Hypertension research. doi:10.1038/s41440-019-0304-9Free full textPubMed 31371810DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error