Long life expectancy could be achieved through eating soy products such as natto, fermented soybeans, miso and tofu. Researchers in Japan analysed the eating habits and health outcomes of more than 90,000 people aged 45-74 to see if soy products had specific health effects.
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Soy products are widely consumed in Asian countries and increasingly so in the West.
The authors did not find a significant association between consuming soy products in general and early death from any cause.
But, they conclude: “In contrast, a higher intake of fermented soy products (natto and miso) was associated with a lower risk of mortality.”
Those who consumed the most fermented soy products were less likely to die from any cause, the researchers found.
Men who consumed at least 50.2g and women who consumed at least 46.6g per day of fermented soy were around 10 percent less likely to die in the 14.8 years of follow up, compared with those who ate the smallest quantity.
Eating at least 26.2g per day of natto was linked to a 24 percent lower risk of death from cardiovascular disease in men and a 21 percent lower risk in women.
The results persisted even after further adjusting for intake of vegetables, which was higher among those consuming larger portions of natto.
Fermented soy products are richer in fibre, potassium and bioactive components than their non-fermented counterparts, which may help explain the link.
The authors urge caution in interpreting their findings, as unmeasured factors could have played a part and the study was observational so cannot establish cause.
One fermented soy food which has been shown to have a range of health benefits is tempeh.
Tempeh is a traditional Indonesian food made from soybeans that have been fermented.
After fermentation, the soybeans are pressed into a compact cake.
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Soybeans contain natural plant compounds called isoflavones, and these have been associated with reduced cholesterol levels.
One review looked at 11 studies and found soy isoflavones were able to significantly decrease both total and LDL cholesterol.
Studies have also shown isoflavones possess antioxidant properties and may reduce oxidative stress.
And research has found supplementing with soy isoflavones may have a favourable effect on several diseases associated with oxidative stress.
One animal study showed soybean isoflavones decrease blood sugar levels in rats with diabetes.
Another study used data from 6,000 households in Japan and found that intake of soy products was associated with a decreased risk of death from heart disease and stomach cancer.
Tempeh is also a good source of calcium, a mineral which is responsible for keeping bones strong, so could help promote bone health.
In one study, 40 elderly women increased their calcium intake through diet or supplements for two years.
Increasing calcium intake decreased bone loss and preserved bone density, compared to control groups.
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