Dietary Isoflavone Intake Research Articles

Soy isoflavone intake and the likelihood of ever becoming a mother: the Adventist Health Study-2.

ObjectivesAs little is known about the possible relationship between the intake of phytoestrogens and female fertility, we investigated the relationship between soy isoflavone intake and the risk of nulliparity and nulligravidity.MethodsA cross-sectional study of 11,688 North American Adventist women aged 30–50 years old with data regarding childbearing. These women were, as a group, characterized by a high proportion (54%) of vegetarians and a healthy lifestyle with a very low prevalence of smoking and alcohol use.ResultsThe mean isoflavone intake (17.9 mg per day) was very high compared to other Western populations. Only 6% of the women indicated no intake of isoflavones. We found, after adjustment for age, marital status, and educational level, an inverse relationship (P=0.05) between isoflavone intake and the likelihood of ever having become a mother. In women with high (≥40 mg/day) isoflavone intake (12% of this group of women), the adjusted lifetime probability of giving birth to a live child was reduced by approximately 3% (95% CI: 0, 7) compared to women with low (<10 mg/day) intake. No relationships were found between the isoflavone intake and parity or age at first delivery in parous women. A similar inverse relationship (P=0.03) was found between the isoflavone intake and the risk of nulligravidity with a 13% (95% CI: 2, 26) higher risk of never have been pregnant in women with high (≥40 mg/day) isoflavone intake. These relationships were found mainly in women who reported problems becoming pregnant.ConclusionThe findings suggest that a high dietary isoflavone intake may have significant impact on fertility.

Association of soy food intake with risk and biomarkers of coronary heart disease in Chinese men

Soy food intake has been associated with a reduced risk of coronary heart disease (CHD) in women, but its association with CHD in men is unclear [ 1 Zhang X. Shu X.O. Gao Y.T. et al. Soy food consumption is associated with lower risk of coronary heart disease in Chinese women. J Nutr. 2003; 133: 2874-2878 PubMed Google Scholar , 2 Zhang X. Gao Y.T. Yang G. et al. Urinary isoflavonoids and risk of coronary heart disease. Int J Epidemiol. 2012; 41: 1367-1375 Crossref PubMed Scopus (38) Google Scholar , 3 Kokubo Y. Iso H. Ishihara J. Okada K. Inoue M. Tsugane S. Association of dietary intake of soy, beans, and isoflavones with risk of cerebral and myocardial infarctions in Japanese populations: the Japan Public Health Center-based (JPHC) study cohort I. Circulation. 2007; 116: 2553-2562 Crossref PubMed Scopus (210) Google Scholar ]. Several studies have found sex differences in the associations of soy intake with metabolic syndrome, endothelial function, and other cardiovascular risk factors [ 4 Pan A. Franco O.H. Ye J. et al. Soy protein intake has sex-specific effects on the risk of metabolic syndrome in middle-aged and elderly Chinese. J Nutr. 2008; 138: 2413-2421 Crossref PubMed Scopus (42) Google Scholar , 5 Teede H.J. Dalais F.S. Kotsopoulos D. Liang Y.L. Davis S. McGrath B.P. Dietary soy has both beneficial and potentially adverse cardiovascular effects: a placebo-controlled study in men and postmenopausal women. J Clin Endocrinol Metab. 2001; 86: 3053-3060 Crossref PubMed Scopus (281) Google Scholar ]. In the Shanghai Men's Health Study [ [6] Cai H. Zheng W. Xiang Y.B. et al. Dietary patterns and their correlates among middle-aged and elderly Chinese men: a report from the Shanghai Men's Health Study. Br J Nutr. 2007; 98: 1006-1013 Crossref PubMed Scopus (100) Google Scholar ], we investigated the association between soy food intake and incident CHD among 55,474 Chinese men (40–74 years) who were free of CHD, stroke, and cancer at baseline (2002–2006). We also examined the associations of soy intake with multiple CHD biomarkers in a subsample of 3885 men who provided fasting blood samples and had no history of major chronic diseases at recruitment.

Diet/Lifestyle Strategies for Preventing Benign Prostatic Hyperplasia

Although benign prostatic hyperplasia (BPH) is often viewed as an inevitable concomitant of the aging process, recent research establishes that this syndrome is significantly more common in men with metabolic syndrome. Moreover, twentieth century epidemiology focusing on quasi-vegan rural China reveals that this syndrome may in fact be substantially preventable. The decline in cellular apoptosis which appears to be a key driver of BPH should be counteracted in part by diet/lifestyle measures which minimize systemic IGF-I activity. Diets moderate in protein and very low in animal products are associated with low plasma IGF-I levels, reflecting decreased hepatic production of this hormone. Leanness, exercise training, and other lifestyle measures which minimize diurnal insulin secretion, have been found to correlate with reduced BPH risk, and can be expected to reduce systemic and prostatic IGF-I/ IGF-II bioactivity by increasing hepatic secretion of IGFBP-1. Apoptosis of prostate cells can also be promoted by selective agonists for estrogen receptor-β; high dietary intakes of soy isoflavones can function as such agonists. Conversion of prostate epithelial and stromal cells to a myofibroblast phenotype by transforming growth factor-β contributes importantly to the expansion of the stromal compartment in BPH; there is reason to suspect that this transition could be opposed by the antioxidant activity of spirulina, AMPK-activating drugs or nutraceuticals, and possibly adiponectin (suggesting a further benefit of leanness). Although calcitriol analogs appear to have potential for preventing and treating BPH, there is no current evidence that dietary modulation of vitamin D status can be beneficial in this regard. Prospects for prevention of BPH may be good in individuals who adopt optimally healthprotective diet, lifestyle, and nutraceutical strategies.

S-(−)equol producing status not associated with breast cancer risk among low isoflavone-consuming US postmenopausal women undergoing a physician-recommended breast biopsy

Soy foods are the richest sources of isoflavones, mainly daidzein and genistein. Soy isoflavones are structurally similar to the steroid hormone 17β-estradiol and may protect against breast cancer. S-(−)equol, a metabolite of the soy isoflavone daidzein, has a higher bioavailability and greater affinity for estrogen receptor β than daidzein. Approximately one-third of the Western population is able to produce S-(−)equol, and the ability is linked to certain gut microbes. We hypothesized that the prevalence of breast cancer, ductal hyperplasia, and overall breast pathology will be lower among S-(−)equol producing, as compared with nonproducing, postmenopausal women undergoing a breast biopsy. We tested our hypothesis using a cross-sectional study design. Usual diets of the participants were supplemented with 1 soy bar per day for 3 consecutive days. Liquid chromatography–multiple reaction ion monitoring mass spectrometry analysis of urine from 143 subjects revealed 25 (17.5%) as S-(−)equol producers. We found no statistically significant associations between S-(−)equol producing status and overall breast pathology (odds ratio [OR], 0.68; 95% confidence interval [CI], 0.23-1.89), ductal hyperplasia (OR, 0.84; 95% CI, 0.20-3.41), or breast cancer (OR, 0.56; 95% CI, 0.16-1.87). However, the mean dietary isoflavone intake was much lower (0.3 mg/d) than in previous reports. Given that the amount of S-(−)equol produced in the gut depends on the amount of daidzein exposure, the low soy intake coupled with lower prevalence of S-(−)equol producing status in the study population favors toward null associations. Findings from our study could be used for further investigations on S-(−)equol producing status and disease risk.

Green Tea Consumption and Breast Cancer Risk in Japanese Women: A Case-Control Study

Although many in vitro and animal studies have suggested a protective effect of green tea against breast cancer, only a few epidemiological studies have examined this association, and findings have been inconsistent. We examined the association between green tea consumption and breast cancer risk in consideration of the hormone receptor status of tumors and investigated whether the association was modified by dietary and genetic factors based on a hospital-based case-control study in Nagano, Japan. A total of 369 pairs completed a validated food frequency questionnaire and provided blood samples. Four single nucleotide polymorphisms (SNPs) were genotyped: CYP19A1 (rs10046), COMT (rs4680), MTHFR C677T (rs1801133), and MTHFR A1298C (rs1801131). We found no inverse association between green tea consumption and breast cancer risk. Compared with women who drank less than 120 ml of green tea per day, the adjusted odds ratio for women who drank more than 600 ml was 1.27 (95% confidence interval = 0.75–2.14; P for trend = 0.20). We also found no inverse association for either tumor subtype. No substantial effect modification was observed for menopausal status, 4 SNPs, or dietary intake of folate or isoflavone. This study provides additional evidence that green tea consumption is not associated with a decreased risk.

Usual dietary isoflavone intake and reproductive function across the menstrual cycle

To assess the association of total isoflavone intake with ovulatory function, including sporadic anovulation in healthy premenopausal women. Prospective cohort study. University. Participants included 259 healthy regularly menstruating women aged 18-44 years. None. Serum concentrations of E2, free E2, P, LH, FSH, and SHBG and sporadic anovulation in healthy premenopausal women. Isoflavone intake was not associated with E2, free E2, P, LH, and FSH concentrations. Consumption in the highest quartile (Q4: 1.6-78.8 mg/d) was significantly associated with greater SHBG concentrations (β = 0.09; 95% confidence interval [CI] 0.02-0.16), compared with the first quartile (Q1: 0.0-0.3 mg/d). Isoflavone intake was not associated with sporadic anovulation (Q4 vs. Q1: odds ratio 0.87, 95% CI 0.32-1.66). Dietary isoflavone intake among young premenopausal women was not related to sex hormone concentrations or anovulation, but was associated with minimally increased SHBG concentrations. These results suggest potential endocrine effects with no subsequent effects on ovulation, easing concerns regarding their impacts on fertility.

Plasma Isoflavone Concentrations Are Not Associated with Gastric Cancer Risk among Japanese Men and Women1,2

The incidence of gastric cancer throughout the world is ∼2–3 times higher in men than in women. Previous research suggested that isoflavones, which are structurally similar to 17β-estradiol, may prevent gastric cancer. Based on a large, population-based, prospective study, we recently reported a null association between dietary isoflavone intake and gastric cancer. However, epidemiologic studies using blood concentrations of isoflavones might better reflect the effect of isoflavones on gastric cancer carcinogenesis than dietary assessment. We therefore conducted a nested case-control study within the Japan Public Health Center-Based Prospective Study. Participants were followed-up from 1990 to 2004. Among 36,745 participants who answered the baseline questionnaire and provided blood samples, 483 gastric cancer cases matched to 483 controls were used in the analysis. ORs and 95% CIs were estimated with a conditional logistic regression model. The overall distribution of plasma isoflavone concentrations was not associated with the development of gastric cancer. Compared with groups with the lowest plasma concentrations (reference groups), the groups with the highest daidzein and genistein concentrations had adjusted ORs and 95% CIs of 1.11 (0.74–1.66; P-trend = 0.6) and 0.96 (0.64–1.44; P-trend = 0.9), respectively. The results did not change when analysis was based on sex, subsite, or histological type. We found no association of plasma isoflavone concentrations with gastric cancer risk. Our data support the previously observed null association between isoflavone intake and gastric cancer risk.

Perspectives on the Role of Isoflavones in Prostate Cancer

Isoflavones have been investigated in detail for their role in the prevention and therapy of prostate cancer. This is primarily because of the overwhelming data connecting high dietary isoflavone intake with reduced risk of developing prostate cancer. A number of investigations have evaluated the mechanism(s) of anticancer action of isoflavones such as genistein, daidzein, biochanin A, equol, etc., in various prostate cancer models, both in vitro and in vivo. Genistein quickly jumped to the forefront of isoflavone cancer research, but the initial enthusiasm was followed by reports on its contradictory prometastatic and tumor-promoting effects. Use of soy isoflavone mixture has been advocated as an alternative, wherein daidzein can negate harmful effects of genistein. Recent research indicates a novel role of genistein and other isoflavones in the potentiation of radiation therapy, epigenetic regulation of key tumor suppressors and oncogenes, and the modulation of miRNAs, epithelial-to-mesenchymal transition, and cancer stem cells, which has renewed the interest of cancer researchers in this class of anticancer compounds. This comprehensive review article summarizes our current understanding of the role of isoflavones in prostate cancer research.

Habitual Dietary Isoflavone Intake Is Associated with Decreased C-Reactive Protein Concentrations among Healthy Premenopausal Women

Isoflavones have been associated with lower cardiovascular disease risk, but existing research focused on very high isoflavone intakes, as seen in Asian populations, as well as on risk factor reductions primarily in postmenopausal women. We investigated whether habitual low isoflavone intake among premenopausal women was associated with serum C-reactive protein (CRP) concentration, a commonly used biomarker associated with prediction of cardiovascular disease risk in healthy women. Between 2005 and 2007, 259 healthy, regularly menstruating women were enrolled in the BioCycle Study, and followed for up to 2 menstrual cycles. CRP was measured in serum at up to 16 clinic visits, timed to phases of the women's menstrual cycle. Diet was assessed up to 4 times per cycle by using 24-h recalls. Marginal structural models with inverse probability of exposure weights estimated the association between CRP and quartiles of isoflavone intake adjusted for age, race, BMI, cycle phase, total energy intake, total fiber, total whole grains, and phase-specific hormone concentrations including estradiol, progesterone, luteinizing hormone, and follicle-stimulating hormone. Compared with the lowest quartile of total isoflavone intake, women in the highest quartile had, on average, 27% lower serum CRP concentrations (95% CI: –35, –21%). Our results suggest that dietary isoflavone intakes at levels characteristic of the U.S. population are associated with decreased serum CRP concentrations, a factor associated with beneficial effects on inflammation, and subsequently may have the potential to improve health status among young women.

Population Versus Hospital Controls in the Assessment of Dietary Intake of Isoflavone for Case-Control Studies on Cancers in China

To assess dietary isoflavone intake between population and hospital outpatient controls and examine if cancer risks estimated for isoflavone using hospital outpatient controls would be different from those using population controls. Three parallel case-control studies on leukemia, breast, and colorectal cancers in China in 2009–2010 were conducted, using population and hospital outpatient controls to separately match 560 incident cases at a 1:1 ratio. A validated food frequency questionnaire was administered by face-to-face interview. Conditional logistic regression analysis was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). The 2 control groups had closely similar distributions of dietary isoflavone intake. Risk estimates for breast cancers were adjusted ORs (95% CI) of 0.39 (0.23–0.66) and 0.31 (0.18–0.55) for daidzein, 0.35 (0.20–0.61) and 0.28 (0.16–0.52) for genistein, 0.66 (0.41–1.08) and 0.53 (0.32–0.88) for glycitein, and 0.53 (0.33–0.85) and 0.43 (0.26–0.71) for total isoflavone using hospital outpatient and population controls respectively. The study found that hospital outpatient controls were comparable to population controls in measured dietary intake of isoflavone in the Chinese hospital setting.

Relationship between dietary phytoestrogens and development of urinary incontinence in midlife women

Because exogenous estrogen treatment has been associated with a higher risk of urinary incontinence, our objective was to evaluate the longitudinal relationships of dietary phytoestrogen intakes (isoflavones, coumestans, and lignans) and the development of incontinence in midlife women transitioning through menopause. The Study of Women's Health Across the Nation (SWAN) Phytoestrogen Study was developed within SWAN, a community-based, multisite, multiracial/ethnic, prospective cohort study. SWAN interviewers administered a food consumption assessment at baseline and on follow-up visits 5 and 9. The SWAN Phytoestrogen Study created a phytonutrient database that allowed estimation of the usual daily intakes of four isoflavones, four lignans, and coumestrol. On an annual self-administered questionnaire, participants reported on the frequency and type of incontinence. We used discrete proportional hazards models to evaluate whether the estimated daily intake of each phytoestrogen class on the visit previous to the first report of incontinence was associated with the development of monthly or more incontinence versus remaining continent. We found no association or patterns of association between developing any, stress, or urge incontinence and the reported daily dietary intake of isoflavones, coumestrol, and lignans on the visit previous to the onset of incontinence. The results of this longitudinal study provide important information to better understand estrogenlike substances in the continence mechanism of midlife women. Our study shows that neither high nor low dietary intakes of isoflavones, coumestrol, and lignans prevent stress or urge incontinence. Future studies should evaluate whether serum levels of phytoestrogens or their metabolites impact incontinence symptoms.

Dietary isoflavone intake modulates evoked responses to cardiometabolic stimuli in healthy volunteers

Isoflavones, found in high concentrations in soy‐derived foods, function as phytoestrogens, have antioxidant and anti‐inflammatory activity, inhibit protein‐tyrosine kinase activity, and are thought to be atheroprotective. We hypothesized that habitual isoflavone intake modulates response to evoked endotoxemia and oral fat load.In the Genetics of Evoked Responses to Niacin and Endotoxemia (GENE) Study, we administered low dose endotoxin (LPS 1 ng/kg) to induce inflammation in young, healthy volunteers (N=215, 50% female) and administered a separate oral fat tolerance test (OFTT). Data were analyzed using linear regression models adjusted for race, gender, age and BMI.Dietary isoflavone intake was a significant predictor of plasma tumor necrosis factor alpha (TNFα) and interleukin 6 (IL‐6) post LPS. High (&gt;;1.5mg/day, N=64) vs low (&lt;1.5mg/day, N=151) isoflavone consumers had higher peak TNFα (64 vs 45 pg/ml, P=0.015) and peak IL‐6 (210 vs 160 pg/ml, P=0.06). Further, the high isoflavone group had significantly higher β‐hydroxybutyrate levels post‐OFTT (442 vs 332 μmol/L, 2 hours post fat load, P=0.02).Habitual isoflavone consumption may modulate disease development through effects on inflammatory and metabolic responses in humans. For investigating nutritional effects on disease development, measuring evoked phenotypes may be more informative than describing resting characteristics.The GENE Study was supported by NIH Grant UL1TR000003 as well as a NIH‐NHLBI SCCOR Project grant (P50‐HL‐083799) to MPR. JFF is supported by an AHA postdoctoral fellowship grant (12POST11840017).

Prediagnosis Soy Food Consumption and Lung Cancer Survival in Women

We recently reported an inverse association between soy food intake and lung cancer risk among nonsmoking women. The effect size for aggressive lung cancers was larger than that observed for other types of lung cancer. Therefore, we hypothesized that soy consumption may favorably affect the overall survival of patients with lung cancer. This analysis included 444 women with incident lung cancer identified from the Shanghai Women's Health Study. Prediagnosis soy food intake was assessed at enrollment and reassessed 2 years later. Proportional hazards models were used to evaluate the association between soy food intake and overall survival. Of the 444 patients with lung cancer, 318 died during follow-up. Initial analyses including all patients showed that higher intake of soy food was associated with better overall survival after adjusting for demographic and lifestyle characteristics and other nonclinical factors. Larger effect sizes for the association were found after additional adjustment for tumor stage and treatment in analyses including 301 patients with data available on these clinical factors. Compared with the median intake of soy food, fully adjusted hazard ratios for total mortality associated with the 10th, 30th, 70th, and 90th percentiles of intake were 1.81 (95% CI, 1.26 to 2.59), 1.25 (95% CI, 1.09 to 1.42), 0.88 (95% CI, 0.80 to 0.97), and 0.89 (95% CI, 0.68 to 1.16), respectively. Similar inverse associations were observed for dietary isoflavone intake. This study suggests, to the best of our knowledge for the first time, that, among women with lung cancer, prediagnosis intake of soy food is associated with better overall survival.

Phytoestrogen and fiber intakes in relation to incident vasomotor symptoms

Although reduction of vasomotor symptoms (VMS; hot flashes and night sweats) has been reported in postmenopausal women who used isoflavones, a clear dose response has not been shown, has largely not been reported for perimenopausal women, and has largely only been reported for reducing prevalent VMS, not preventing newly developing VMS. We analyzed longitudinal data from the Study of Women's Health Across the Nation for the relation of dietary phytoestrogen and fiber intake to incident VMS in this multiracial/ethnic cohort. The Study of Women's Health Across the Nation included 3,302 premenopausal and early perimenopausal women, 1,651 of whom reported no VMS at baseline and were followed with annual visits for 10 years. Dietary intakes of isoflavones, coumestrol, lignans, and fiber were assessed by a food frequency questionnaire at baseline and in annual visits 5 and 9 and interpolated for intervening years. The number of days experiencing VMS in the past 2 weeks was self-reported annually. Using multinomial logistic regression with generalized estimating equations, we modeled incident VMS in relation to isoflavones, lignans, fiber, coumestrol, or total phytoestrogen intake and covariates. No consistent monotonic relations were observed between any dietary phytoestrogen or fiber and incident VMS, although adjusted odds ratios for some individual quartiles were statistically significant. For certainty of any effect of dietary phytoestrogens or fiber on the prevention of incident VMS, a randomized, placebo-controlled, double-masked trial with sufficient numbers of women in different racial/ethnic, menopausal status, and metabolic groups over years of follow-up is required, but our results suggest that a clinically significant or large effect is improbable.

Dietary Isoflavone Intake, Urinary Isoflavone Level, and Their Relationship with Metabolic Syndrome Diagnostic Components in Korean Postmenopausal Women

Recent studies have suggested that natural agents such as isoflavones, resveratrol, and anthocyanin have beneficial effects on metabolic syndrome-related disorders. The objective of this study was to evaluate dietary isoflavone intake, urinary isoflavone level, and their relationship with the risk of metabolic syndrome (MetS) among Korean postmenopausal women. The subjects included 46 MetS and 60 controls. The MetS risk score was determined by adding the number of risk factors such as waist circumference, blood pressure (BP) and levels of triglyceride (TG), HDL-cholesterol, and glucose. Dietary isoflavone intake was not significantly different between the MetS and control groups; however, the urinary daidzein level was significantly higher in the MetS subjects compared to that of the controls. Subjects with high TG had higher urinary daidzein and isoflavone (daidzein + genistein) levels than those without such abnormalities. But, the MetS risk score showed no significant correlation with urinary daidzein, genistein, and isoflavone excretions.

Preliminary investigation of the influence of long-term dietary isoflavone intake on puberty onset and oestrous cycles in domestic cats (Felis catus)

SummaryGenistein and daidzein are isoflavones which are reported to influence the reproductive system in a variety of mammalian species. This pilot study aimed to determine if dietary isoflavones could potentially influence reproductive parameters in domestic cats, when consumed during the postnatal development period. Cats (n = 12) were maintained on either a treatment (150 µg/g DM genistein and 150 µg/g DM daidzein, n = 4) or control (isoflavone free, n = 8) diet from weaning, up to 414 (±17.2) days post-weaning. Vaginal smears were taken thrice weekly and examined for oestrogen-induced cellular degradation in all cats. Behavioural indicators of oestrous were routinely scored for the presence or absence of six key behaviours. Genistein and daidzein did not alter puberty onset or oestrous cycle parameters in these cats (P &gt; 0.05). Behavioural scores were higher in cats in the treatment group than control. Incidence of apparent spontaneous ovulation (inferred from extended inter-oestrous periods) was greater in treated cats than control cats, although serum hormone profiles were not available to confirm this observation. Further testing is warranted.

Dietary phytoestrogen intakes and cognitive function during the menopausal transition: results from the Study of Women's Health Across the Nation Phytoestrogen Study.

Phytoestrogens, which consist mainly of isoflavones, lignans, and coumestans have estrogenic and anti-inflammatory properties. Previous research suggests that higher dietary or supplemental intakes of isoflavones and lignans are related to better cognitive performance in middle-aged and older women. We conducted longitudinal analysis of dietary phytoestrogens and cognitive performance in a cohort of African American, white, Chinese, and Japanese women undergoing the menopausal transition. The tests were Symbol Digit Modalities, East Boston Memory, and Digits Span Backward. Phytoestrogens were assessed using the Food Frequency Questionnaire. We modeled each cognitive score as a function of concurrent value of the primary predictors (highest tertile of isoflavones, lignans, or coumestrol) and covariates including the menopausal transition stage. Coumestrol and isoflavone intakes were 10 and 25 times greater, respectively, in Asian than in non-Asian participants. During late perimenopause and postmenopause, Asian women with high isoflavone intakes did better on processing speed, but during early perimenopause and postmenopause, high-isoflavone Asian consumers performed worse on verbal memory. The highest isoflavone consumers among non-Asians likewise posted lower verbal memory scores during early perimenopause. A verbal memory benefit of higher dietary lignan consumption was apparent only during late perimenopause, when women from all ethnic/racial groups who were in the highest tertile of intake demonstrated a small advantage. Coumestrol was unrelated to cognitive performance. The cognitive effects of dietary phytoestrogens are small, seem to be class-specific, vary by menopause stage and cognitive domain, and differ among ethnic/racial groups (but whether this is related to dose or to host factors cannot be discerned).

Relationship between isoflavone intake and metabolic syndrome diagnostic components in Korean postmenopausal women

Recent studies have suggested that natural agents such as isoflavones, resveratrol, and anthocyanin have beneficial effects on metabolic syndrome (MetS)‐related disorders. The objective of this study was to evaluate among isoflavone intake, urinary isoflavone level, and the risk of MetS among Korean postmenopausal women. The subjects included 46 MetS and control (n=60). The MetS risk score was determined by adding the number of risk factors such as waist circumference and high levels of triglyceride (TG), HDL‐cholesterol, glucose, and blood pressure (BP). Dietary isoflavone intake was not significantly different between MetS and control groups; however, the urinary daidzein level was significantly higher in MetS subjects compared to that of the controls. Subjects with high TG had higher urinary daidzein and isoflavone levels than those without such abnormalities. The correlation analysis indicated that dietary isoflavone intake had a positive relation with energy intake. After adjusted energy intake, there was no significant relationship among isoflavone intake, metabolic syndrome, and its components in Korean postmenopausal women. These results indicate that women who have more dietary isoflavones tend to have more energy. Furthermore, this study shows no significant direct relationship between isoflavone intake and risk of MetS in Korean postmenopausal women.

Soy foods and urinary isoprostanes: Results from a randomized study in premenopausal women

In addition to their antiestrogenic effects, soy isoflavones may protect against cancer through alternate biological actions, for example, antioxidant properties. This randomized crossover study explored the relationship between dietary isoflavone intake through common soy foods and oxidative stress quantified by urinary isoprostane levels. Eighty-two women aged 39.2 ± 6.1 years were randomly selected to receive a high soy diet of 2 soy food servings per day and a low soy diet of <3 servings per week for 6 months each, separated by a 1-month washout period. Urine samples were collected at baseline and at the end of each dietary period. Urinary isoprostane levels were measured using enzyme-linked immunosorbent assays (ELISA) and adjusted for creatinine levels. Mixed models using log-transformed values were applied to evaluate the effect of the high soy diet. Unadjusted isoprostane excretion levels were lower during the high rather than the low soy diet, but this effect was not statistically significant (p = 0.81). After adjustment for urinary creatinine, isoprostane excretion was slightly higher during the high soy diet (p = 0.02), an observation that was confirmed in a regression analysis between urinary isoflavones and isoprostanes during the high soy diet. The original association remained significant when restricted to adherent participants, however this effect disappeared after exclusion of three extreme values. In agreement with several previous reports, these findings do not support the hypothesis that soy exerts antioxidant effects, as measured by urinary isoprostane excretions, but additional markers of oxidative stress need to be investigated in future studies.

Isoflavone intake and risk of gastric cancer: a population-based prospective cohort study in Japan

Isoflavones are structurally similar to 17β-estradiol and may be able to prevent gastric cancer. However, there is contradictory evidence concerning the relation between the intake of soy food, which is rich in isoflavones, and gastric cancer. The association with gastric cancer might differ between isoflavones and soy foods, and research on the effects of isoflavone intake alone on gastric cancer is needed. We investigated the association between isoflavone intake and the incidence of gastric cancer. We conducted a large, population-based prospective study of 39,569 men and 45,312 women aged 45-74 y. Dietary soy and isoflavone intakes were measured by using a validated food-frequency questionnaire in 1995 and 1998. During 806,550 person-years of follow-up, we identified 1249 new gastric cancer cases. Isoflavone intake was not associated with gastric cancer in either men or women. Compared with the lowest quartile, the HR and 95% CI for developing gastric cancer in the fourth quartile of isoflavone intake was 1.00 (0.81, 1.24) for men and 1.07 (0.77, 1.50) for women. In a stratified analysis by exogenous female hormones (women only), however, we found an increasing trend in risk of gastric cancer associated with higher isoflavone intakes among exogenous female hormone users (P-trend = 0.03) but not for nonusers (P-interaction = 0.04). The current study does not support the hypothesis that higher intakes of isoflavones prevent gastric cancer in either men or women.