Hypertension: Miso is commonly served as a soup, with 1-2 grams of salt in each bowl (Saeed, 2022; Ito, 2020). The high salt content might theoretically cause concern for hypertension; however, frequency of miso soup consumption has not been associated with elevated blood pressure (Ito, 2020). Eating fermented soy products is inversely associated with developing high blood pressure (BP) in normotensive men and women (Nozue, 2017; Kanda, 1999). Regular miso intake decreases nighttime BP in patients with Stage 1 HTN or high-normal BP but does not affect daytime BP (Kondo, 2019).
Miso's hypotensive effect may be multifactorial:
inhibiting the angiotensin-converting enzyme (ACE) activity causing diuresis, kidney sodium excretion, and inhibition of the reabsorption of sodium in the renal tubules (Takahashi, 2021)
enhancing dopaminergic nervous activity in the kidney (Du, 2014).
CVD: High fermented soy intake (miso and natto) was inversely related to both risk of CVD and stroke in women, but not men (Nozue, 2021).
Obesity: The prevalence of obesity in diabetic (T2DM) patients with habitual miso consumption was less than diabetic patients without habitual miso consumption (Takahashi, 2021).
Insulin resistance: Daily miso consumption in women (but not men) was associated with lower insulin resistance (Hashimoto, 2023; Ikeda, 2018).
Diabetes: Women (but not men) with T2DM who consume miso daily had improved glycemic control, including glycemic variability (as an independent variable) as compared to diabetic female non-consumers of miso (Takahashi, 2021). Cross-sectional studies have shown better glucose control and improvements in body composition in diabetic men and women that eat miso (Hashimoto, 2023).
GERD: Daily miso soup intake was associated with fewer epigastric symptoms (Mano, 2018).
Cancer: An inverse relationship was found between miso intake and liver cancer in men, but not women (Abe, 2021). Higher intake of fermented soy products was associated with a decrease in nonlocalized breast cancer but not overall breast cancer (Shirabe, 2021).
Mortality: Higher intake of miso and natto were inversely related to all-cause mortality in women only with a 10% lower risk from the highest to the lowest quintile. Cardiovascular disease mortality was inversely associated with natto consumption for both men and women (Katagiri, 2020).
The differential effects of miso and soy in women and men may reflect the phytoestrogenic actions of soy or gender-based differences in the microbiome.