Traditional Asian diets include many types of soy products including tofu and fermented foods like natto, miso, and tempeh. Recent studies have shown that fermented soy products, not total soy intake, are associated with a lower risk of high blood pressure. Fermented soy products, which are made from whole soybeans, contain healthful isoflavones and fiber as well as bioactive components such as polyamine. However, few studies have looked at the effect of fermented soy products on mortality.
Researchers conducted a prospective cohort study which followed 92,915 Japanese women and men aged 45 to 74 over 15 years. They reviewed the participants’ intake of total soy products, fermented soy products, non-fermented soy products, and tofu from 5-year survey questionnaires and observed their all-cause and cause specific (e.g. cancer, cardiovascular disease, etc.) mortality.
Of the nearly 93,000 participants, a little over 13,000 died. After controlling for diabetes, BMI, smoking status, physical activity, and other confounders, researchers found that those in the highest one-fifth for fermented soy intake had a 10% lower risk of death from any cause as compared to those in the lowest one-fifth. Natto intake was associated with an 18% lower risk of death from cardiovascular disease.
The strengths of this study were the long follow-up time and large sample; however, the authors noted that there were other confounding variables they could not account for.
Despite these limitations, the researchers note that a diet high in fermented soy is associated with lower mortality and may be especially beneficial in terms of cardiovascular health.
Katagiri, R. et al. (2020). Association of soy and fermented soy product intake with total and cause specific mortality: prospective cohort study. BMJ, 368, m(34).
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