A new study published in the British Medical Journal found that eating large amounts of fermented soy products, such as miso and natto, reduces the risk of death. In Asian countries, especially Japan, several soy products are widely consumed, such as natto (soy products fermented with herbbacher, soy with herbbacillus), miso (soybeans fermented with rice closther) and tofu.
So a team of researchers in Japan began investigating the relationship between several soy products and all-cause mortality, as well as cancer, cardiovascular disease (heart and cerebrovascular disease), respiratory diseases and injuries.
The study was based on data from a study of 11 public health centers in Japan involving 42,750 men and 50,165 women. Participants filled out detailed questionnaires about their eating habits, lifestyle and health. During nearly 15 years of follow-up, deaths were confirmed from the resident registry and death certificates.
The researchers found that eating more fermented soy (natto and miso) significantly reduced (10 percent) of all-cause mortality, but the total intake of soy products was not related to all-cause mortality.
Men and women who ate natto had lower cardiovascular mortality rates than those who did not, but there was no association between soy intake and cancer-related mortality. Even if the intake of vegetables was further adjusted, these results persisted, and the intake of vegetables was higher among people who ate large amounts of natto.
In the large-scale prospective study conducted in Japan, the researchers said that although soybean consumption rates were high, no significant link was found between total soy product intake and all-cause mortality. In contrast, the more fermented soy products (natto and miso) are eaten, the lower the mortality rate.
The researchers note that fermented soy products are more rich in fiber, potassium and bioactive ingredients than unfermented soy products, which may help explain their connection. The researchers also stressed that this is only an observational study, so the cause cannot be determined, nor does it exclude some of the factors affected by unmeasured mixing factors.