High-soy diets contribute to a long life
21 Dec 2021
Isoflavones – plant-derived phytoestrogens with similar effects as the female hormone oestrogen – often found in soy products, have vastly different effects in women and men.Diets high in isoflavones appear to reduce the risk of all-cause mortality among middle-aged adults, reports a recent Japan study.
The study included 2,136 randomly chosen community-dwelling adults aged 40–79 years who were followed for an average period of 16.6 years. Three-day dietary records with photographs were used to assess intake levels of legumes, soy foods, and overall isoflavones, taking particular note of food items such as soybeans, tofu, miso, and other bean products. The outcome of interest was all-cause mortality.
A total of 491 all-cause deaths were reported. Survivors tended to be women and were younger than those who died. Grouping patients according to tertiles of isoflavone intake revealed a significant impact on mortality.
For instance, Cox proportional hazards analysis found an inverse dose-response interaction in adults aged <60 years. Those in the highest category of consumption for soy products were nearly 70 percent less likely to die of any cause compared with the lowest tertile (hazard ratio [HR], 0.32, 95 percent confidence interval [CI], 0.13–0.78).
Excluding seasonings slightly weakened the effect of high-soy consumption but did not attenuate significance (HR, 0.40, 95 percent CI, 0.17–0.92). Similarly, the highest tertile of isoflavone intake suppressed all-cause mortality risk by 65 percent (HR, 0.35, 95 percent CI, 0.17–0.73).
Notably, soy and isoflavone intake had no such effect on mortality risk in adults aged ≥60 years.
“Larger prospective studies should be conducted in the future to examine the associations of intake amounts of soy products and/or isoflavones with all-cause mortality and cause- specific disease mortality after stratification into sex and according to age group and/or menopausal status,” the researchers said.