Soy product intake and risk of incident disabling dementia: the JPHC Disabling Dementia Study

Abstract

Purpose We evaluated the association between total soy, soy product (natto, miso and tofu) and isoflavone intake and incident disabling dementia in a Japanese population. Methods We conducted a population-based prospective study in 18,991 men and 22,456 women. Intake of soy products and isoflavone was calculated using a validated food frequency questionnaire when participants were 45–74 years old (1995 and 1998). Incident disabling dementia was defined by the daily living disability status related to dementia in the long-term care insurance program of Japan from 2006 to 2016. Multivariate hazard ratios (HRs) and 95% confidence intervals (CIs) of disabling dementia were calculated by quintiles of total soy, individual soy product and isoflavone intake, using Cox proportional hazard regression models. Results Total soy product intake was not associated with disabling dementia risk in both men and women. By individual soy products, natto intake was marginally inversely associated with disabling dementia in women (trend P = 0.050). When we stratified by age, this inverse association was clearer in women aged under 60 years (multivariate HR for the highest versus lowest quintile was 0.78, 95% CI 0.59–1.04, trend P = 0.020 for those aged under 60 years and 0.90, 95% CI 0.77–1.05, trend P = 0.23 for those aged 60 years and older, respectively). Any soy product or isoflavone intake was not associated with disabling dementia risk in men. Conclusions Although total soy product intake was not associated with disabling dementia risk, natto intake may contribute to reducing the risk of disabling dementia in women, especially in those aged under 60 years.

The health effects of soy: A reference guide for health professionals

“…More recently, a Japanese prospective observational study found higher midlife genistein intake was associated with cognitive impairment (252) although these results contrast with an earlier prospective observational study from Japan that found soyfood and isoflavone intake decreased risk of cognitive impairment in elderly women (253). They also contrast with the results of a large prospective Japanese study involving more than 40,000 adult men and women which found soyfood intake was unrelated to the development of disabling dementia over the approximate 20 year follow up period (254).…”

Soy isoflavone ameliorated the alterations in circulating adipokines and microRNAs of mice fed a high-fat diet

“…According to a population-based prospective study, the daily estimated mean intake of total isoflavone by US adults was reported to be 2.35 mg. 41 Meanwhile, daily consumption of isoflavone (median value of Q1 to Q5) ranged from 14.0 to 73.1 mg day −1 and from 14.5 to 72.8 mg day −1 in Japanese men and women, respectively. 42 The isoflavone contents in soy-based foods that are typically consumed by Eastern Asian counties were in the range of ∼20 to 80 mg per serving. 43…”

“…According to a population-based prospective study, the daily estimated mean intake of total isoflavone by US adults was reported to be 2.35 mg. 41 Meanwhile, daily consumption of isoflavone (median value of Q1 to Q5) ranged from 14.0 to 73.1 mg day −1 and from 14.5 to 72.8 mg day −1 in Japanese men and women, respectively. 42 The isoflavone contents in soy-based foods that are typically consumed by Eastern Asian counties were in the range of ∼20 to 80 mg per serving. 43 In previous studies, consuming similar (∼200 to 500 mg kg −1 ) or higher amounts (1 to 4 g kg −1 ) of pure isoflavone, either genistein or daidzein, during various periods (12 to 24 weeks) reduced body weight in diet-induced obese rodent models.…”

Phytoestrogens and Health Effects

“…Isoflavones are currently the most present phytoestrogens in the human environment due to the adoption of vegan diets and the use of soybeans for both soy-based foodstuffs and transformed foodstuffs. While isoflavone exposure in China was recently evaluated in more than 53,000 people to range from 0.8 to 78.0 mg/day (median: 13.5 mg/day; IQR: 7.7, 21.4 mg/day) [ 62 ], the isoflavone exposure in Japan [ 63 ](estimated on more than 30,000 people) ranged from 14 to 75 mg/day. In Western countries, the isoflavone intake is currently considered to be lower: a few mg/day in the general population.…”