High intake of fermented soy products may reduce risk of death

04 Feb 2020 byStephen Padilla
Nattō, a Japanese delicacy, was found to be from a prefecture facing a ban on food imports. However, the radiation levels werNattō, a Japanese delicacy, was found to be from a prefecture facing a ban on food imports. However, the radiation levels were still exceedingly low to be a threat.

High consumption of fermented soy products, such as natto and miso, appears to lower the risk of mortality, according to a Japan study. However, no significant association exists between intake of total soy products and all-cause mortality.

“Our findings should be interpreted with caution because the significant association of fermented soy products could be attenuated by unadjusted residual confounding,” the researchers said.

A total of 13,303 deaths were identified during a follow-up of 14.8 years. Total soy products intake did not significantly correlate with total mortality in multivariable-adjusted models. The highest fifth of total soy product intake, compared with the lowest fifth, showed a hazard ratio (HR) of 0.98 (95 percent confidence interval [CI], 0.91–1.06; ptrend=0.43) in men and 0.98 (95 percent CI, 0.89–1.08; p-trend=0.46) in women. [BMJ 2020;368:m34]

On the other hand, an inverse association was found between consumption of fermented soy products and all-cause mortality in both men and women (highest vs lowest fifth: HR, 0.90, 95 percent CI, 0.83–0.97; p-trend=0.05; HR, 0.89, 95 percent CI, 0.80–0.98; p-trend=0.01, respectively). Of note, natto intake significantly correlated with lower total cardiovascular disease (CVD)-related death in both sexes.

These results were consistent with those of an earlier Japan study which examined the association between natto intake and CVD-associated mortality. [Am J Clin Nutr 2017;105:426-431]

“Although both miso and natto are fermented soy products, only natto intake showed a significant reduction in CVD-related mortality in our study, possibly because its sodium content (a risk factor for CVD) is lower than that of miso,” the researchers said. [www.who.int/cardiovascular_diseases/guidelines/Full%20text.pdf]

Soy products possess bioactive components that can “modulate their effects on mortality,” they added. Notably, nutrients such as isoflavone, fibre and potassium appear to play major roles on the link between soy consumption and CVD. [Circulation 2007;116:2553-2562; Epidemiology 2013;24:726-733.; Am J Clin Nutr 2017;105:426-431]

Previous studies suggested the effects of isoflavone in reducing blood pressure and improving lipid profile properties, and that of fibre in lowering cholesterol levels and inducing weight loss. [Mol Nutr Food Res 2013;57:2147-2154; J Am Diet Assoc 1991;91:816-819; J Hypertens 2010;28:1971-1982; Am J Clin Nutr 2007;85:1148-1156]

Fermented soy products have more fibre and potassium, as well as bioactive components, than nonfermented products such as tofu, according to the researchers. These bioactive components include the fibrinolytic enzyme nattokinase and polyamine. [Biosci Biotechnol Biochem 1997;61:1582-1584; Experientia 1987;43:1110-1111]

The present population-based cohort study included 92,915 participants (50,165 women) aged 45–74 years from 11 public health centre areas in Japan. Participants completed a 5-year questionnaire on their intake of total soy products, fermented soy products (natto and miso), nonfermented soy products and tofu.

Study endpoints included all-cause and cause-specific mortality (ie, cancer, total CVD, heart disease, cerebrovascular disease, respiratory disease and injury) obtained from residential registries and death certificates.