People who eat lots of miso and other fermented soy products may get to enjoy them for a long time, according to a Japanese study that links eating these foods with a lower risk of premature death.
Middle aged and older men who ate the most fermented soy were about 10% less likely to die prematurely of all causes than men who rarely ate these foods, the study found, while women who ate the most fermented soy had an 11% lower risk of premature death.
Tofu, however, wasn't associated with longer life. And total soy consumption didn't seem to impact longevity either.
"Fermented soy products such as miso and natto might have a beneficial effect on longevity, but we need to pay attention to salt contents, especially in miso," said Kayo Kurotani of the National Institutes of Biomedical Innovation in Tokyo.
Natto, made from soybeans fermented with Bacillus subtilis, is often served for breakfast in Japan. Miso - soybeans fermented with Aspergillus oryzae - is often prepared as a paste and mixed into a variety of Japanese sauces and soups.
These foods are staples of a traditional Japanese diet, along with tofu, or soybean curd, and abura-age, or fried tofu, researchers note in the The BMJ.
"We already realized potential effects of soy on health," Kurotani, co-author of an editorial accompanying the study, said by email.
Soy is rich in protein, fiber and healthy unsaturated fats. Previous research has linked soy to lower cholesterol and a lower risk of heart disease. Past studies have also linked soy to a lower risk of premature death, but results have been mixed and offered an unclear picture of how much soy or what types of soy-based foods might make the biggest difference.
More than 70% of deaths worldwide are caused by chronic diseases, like heart disease, that are influenced by the way people eat, the study team notes. So they wanted to see which forms of soy might have the most potential to help people live longer.
For the study, they followed almost 93,000 adults, ages 45 to 74, for about 15 years, on average, to see how eating habits impacted survival odds in general and the risk of cardiovascular diseases specifically.
Natto, in particular, was associated with a lower risk of dying from cardiovascular diseases. Men who ate the most natto were 24% less likely than those who rarely ate it to die from cardiovascular causes during the study, while women who ate lots of natto had a 21% lower risk of dying from cardiovascular causes.
The connection between fermented soy and longevity persisted even after researchers accounted for other aspects of people's diets, like their vegetable consumption.
The study cannot prove fermented soy is the reason for the lowered risk.
Still, study co-author Dr. Norie Sawada of the National Cancer Center in Tokyo noted that eating fermented soy might be linked to better overall health or longer life in part because it's associated with lower blood pressure, lower cholesterol and lower body weight.
"In this large prospective study conducted in a country with a high level of soy consumption, intake of fermented soy products, including natto and miso, were significantly associated with reduced all-cause mortality," Sawada said by email.
SOURCE: https://bit.ly/31yj9ym and https://bit.ly/2H6stA5 The BMJ, online January 29, 2020.