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.
World's oldest people
World's oldest people
In this Aug. 23, 2018 photo, 117-year-old Julia Flores Colque speaks during an interview at her home in Sacaba, Bolivia. The previously world's oldest person, a 117-year-old Japanese woman, died earlier this year. Her passing apparently left Flores Colque as the world's oldest living person. (AP Photo/Juan Karita)
The world's oldest person Violet Brown clasps her hands at her home in Duanvale, Jamaica, Sunday, April 16, 2017. The 117-year-old woman living in the hills of western Jamaica is believed to have become the world's oldest person, according to groups that monitor human longevity. (AP Photo/Raymond Simpson)
The world's oldest person Violet Brown poses for a photo at her home in Duanvale, Jamaica, Sunday, April 16, 2017. The 117-year-old woman living in the hills of western Jamaica is believed to have become the world's oldest person, according to groups that monitor human longevity. (AP Photo/Raymond Simpson)
FILE - In this Tuesday, Nov. 29, 2016 file photo, Emma Morano sits in her home on the day of her 117th birthday in Verbania, Italy. An Italian doctor says Emma Morano, at 117 the world's oldest person, has died in her home in northern Italy. Dr. Carlo Bava told The Associated Press by telephone that Morano's caretaker called him to say the woman had passed away Saturday, April 15, 2017 afternoon while sitting in an armchair in her home in Verbania, a town on Lake Maggiore. (AP Photo/Antonio Calanni, File)
FILE - In this Tuesday, Nov. 29, 2016 file photo, Emma Morano, 117 years old, blows candles on the day of her birthday in Verbania, Italy. An Italian doctor says Saturday, April 15, 2017 Emma Morano, at 117 the world's oldest person, has died in her home in northern Italy. Dr. Carlo Bava told The Associated Press by telephone that Morano's caretaker called him to say the woman had passed away Saturday afternoon while sitting in an armchair in her home in Verbania, a town on Lake Maggiore. (AP Photo/Antonio Calanni, File)
FILE - In this Thursday, July 3, 2014, file photo, Gertrude Weaver poses at Silver Oaks Health and Rehabilitation Center in Camden, Ark., a day before her 116th birthday. With the death of a 117-year-old woman in Japan, Weaver became the world's oldest person, according to the Los Angeles-based Gerontology Research Group, which tracks supercentenarians. (AP Photo/Danny Johnston, File)
FILE - In this Feb. 1, 2011 file photo, Besse Cooper, sits in her room at a nursing home, in Monroe, Ga. Cooper, the woman who was listed as the world's oldest person has died Tuesday, Dec. 4, 2012 in a Georgia nursing home at age 116, according to her son Sidney Cooper. (AP Photo/David Goldman, File)
Edna Parker, 114, responds to a question asked by reporters in Shelbyville, Ind., Thursday, Aug. 16, 2007. The world's oldest person _ 114-year-old Edna Parker _ celebrated her feat of longevity Thursday by dining on a slice of her favorite type of cake after telling reporters that she can't believe she's lived to be so old. Parker, who was born in 1893, became the world's oldest person Monday when a Japanese woman four months older than her died. (AP Photo/Darron Cummings)
114 year old Walter Breuning stands under a portrait of himself in the lobby of his senior residence in Great Falls, Mont, on Oct. 6, 2010. Officials at a Montana retirement home say the world's oldest man has died. Walter Breuning was 114, making him the oldest man and the second-oldest person in the world. Breuning was born on Sept. 21, 1896, in Melrose, Minn., and moved to Montana in 1918. Breuning lived at the Rainbow Senior Living retirement home in Great Falls. Retirement home spokeswoman Stacia Kirby confirmed that Breuning died Thursday, April 14, 2011 of natural causes in a Great Falls hospital. (AP Photo/Mike Albans)
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SOURCE: https://bit.ly/31yj9ym and https://bit.ly/2H6stA5 The BMJ, online January 29, 2020.