Equol Excretion Research Articles

Urinary Equol and Equol-Predicting Microbial Genera Are Favorably Associated with Body Fat Measures among Chinese Adults

BackgroundMany studies have investigated the intake of dietary isoflavones in relation to obesity risk, whereas the association using objective biomarkers of isoflavones, particularly equol (a gut-derived metabolite of daidzein with greater bioavailability than other isoflavones) has been less studied. In addition, the associations between equol and gut microbiota profile at the population level remain to be fully characterized. ObjectivesWe aimed to identify equol-predicting microbial species and to investigate the associations of equol-predicting microbial species and urinary excretion of isoflavones including glycitein, genistein, daidzein, and equol with diverse obesity markers in free living-individuals. MethodsIn this 1-y longitudinal study of 754 community-dwelling adults, urinary isoflavones, fecal microbiota, height, weight, and circumferences of waist and hip were measured at baseline and again after 1 y. Liver fat [indicated by the controlled attenuation parameter (CAP)] and other body composition were also measured after 1 y. Linear models and linear mixed-effects models were used to analyze the associations for single measure and repeated measures, respectively. ResultsAmong 305 participants (median age: 50 y, IQR, 37–59 y) including 138 males and 167 females, higher urinary excretion of equol was associated with lower CAP (β = −0.013, P < 0.001) and body fat mass (β= −0.014, P = 0.046). No association was found between any other urinary isoflavones and obesity markers (all P > 0.05). We identified 21 bacterial genera whose relative abundance were positively associated with urinary equol concentrations (all Pfalsediscovery rate < 0.05), and constructed an equol-predicting microbial score to reflect the overall equol-producing potential of host gut microbiota. This score was inversely associated with CAP (β = −0.040, P = 0.011). ConclusionsHigh urinary equol concentrations and equol-predicting microbial species could be favorably associated with liver fat and other obesity markers.

Urinary phytoestrogens and the risk of uterine leiomyomata in US women

BackgroundUterine leiomyomata (UL) is a common gynecological disease in women. Studied on the relationship between single metabolites of urinary phytoestrogens and UL, especially for the combined effects of mixed metabolites on UL still are insufficient.MethodsIn this cross-sectional study, we included 1,579 participants from the National Health and Nutrition Examination Survey. Urinary phytoestrogens were assessed by measuring urinary excretion of daidzein, genistein, equol, O-desmethylangolensin, enterodiol and enterolactone. The outcome was defined as UL. Weighted logistic regression was used to analyze the association between single metabolites of urinary phytoestrogens and UL. Notably, we adopted the weighted quantile sum (WQS) regression, Bayesian kernel machine regression (BKMR), and quantile g-computation (qgcomp) models, to investigate the combined effects of six mixed metabolites on UL.ResultsThe prevalence of UL was approximately 12.92%. After adjusting age, race/ethnicity, marital status, drinking status, body mass index, waist circumference, menopausal status, ovary removed status, use of female hormones, hormones/hormone modifiers, total energy, daidzein, genistein, O-desmethylangolensin, enterodiol, and enterolactone, the association of equol with UL was significant [Odds ratio (OR) = 1.92, 95% confidence interval (CI): 1.09–3.38]. In the WQS model, mixed metabolites of urinary phytoestrogen had a positive association with UL (OR = 1.68, 95%CI: 1.12–2.51), with the highest weighted chemical of equol. In the gpcomp model, equol had the largest positive weight, followed by genistein and enterodiol. In the BKMR model, equol and enterodiol have positive correlation on UL risk, while enterolactone has negative correlation.ConclusionOur results implied a positive association between the mixed metabolites of urinary phytoestrogen and UL. This study provides evidence that urinary phytoestrogen-metabolite mixture was closely related to the risk of female UL.

Prospective association of dietary soy and fibre intake with puberty timing: a cohort study among Chinese children

sBackgroundDietary phytoestrogens have been suggested to influence puberty timing, a critical stage for well-being in adulthood. We hypothesized that childhood soy intake might prospectively influence puberty timing and that dietary fibre and the key isoflavone metabolite equol might play roles.MethodsCox proportional hazard regression models were performed in 4781 children (2152 girls and 2629 boys) aged 6–8 years old from the Chinese Adolescent Cohort Study for whom a food frequency questionnaire at baseline and information about potential confounders were available. Anthropometry and pubertal status including age at Tanner stage 2 for breast development (B2) or age at the initiation of gonadal growth (G2), and age at menarche (M) or voice break (VB) were assessed annually. Equol excretion was determined by urine samples from 1311 participants.ResultsAmong girls and boys, higher soy intake was associated with later puberty timing (hazard ratio (HR)-B2: 0.88 (95% CI, 0.80–0.96), p=0.02; HR-M, 0.87 (0.77–0.94), p=0.01; HR-G2, 0.91 (0.82–0.98), p=0.013; HR-VB, 0.90 (0.82–0.9), p=0.02), independent of prepubertal body fatness and fibre intake. These associations were more pronounced among children with a high urinary equol level (pfor-interaction ≤ 0.04) or with a high cereal fibre intake (pfor-interaction ≤ 0.06). Intake of dietary fibre or its subtype was not prospectively associated with puberty onset after adjusting for dietary soy intake (p≥0.06).ConclusionHigher childhood soy intake is prospectively associated with later puberty timing in both Chinese girls and boys, independent of prepubertal body fatness, and the association is particularly pronounced among individuals with a higher urinary equol level.

Use of high throughput amplicon sequencing and ethidium monoazide dye to track microbiota changes in an equol-producing menopausal woman receiving a long-term isoflavones treatment.

This work describes the impact of long term consumption of an isoflavone-rich dietary daily supplement on the composition and diversity of the faecal microbiota of a menopausal, equol-producing woman. Sequencing of 16S rDNA amplicons was performed on faecal samples taken at 0, 1, 3 and 6 months of treatment. Additionally, and for comparative purposes, ethidium monoazide (EMA) was used to avoid detection of DNA from dead bacteria. Members of two genera of the family Coriobacteriaceae (Eggerthella and Collinsella) were found in greater proportions at all sampling points during isoflavone supplementation. Different genera of the family Ruminococcaceae (e.g., Ruminococcus and Faecalibacterium), as well as members of the family Lachnospiraceae (Coprococcus) also underwent significant increases. For this last genus a positive correlation with the levels of equol excretion in urine was found. Currently bacterial strains known to be involved in isoflavone metabolism and equol production have been assigned to these taxa. The use of EMA dye allowed us to unravel those bacterial gut linages (e.g., Lachnospiraceae) that were more susceptible to damage. Our study contributes to the identification of microorganisms possibly involved in the production of isoflavone-desirable metabolites (such as equol), which could ultimately be isolated and further used as probiotics by people who cannot naturally benefit from isoflavones.

Use of high throughput amplicon sequencing and ethidium monoazide dye to track microbiota changes in an equol-producing menopausal woman receiving a long-term isoflavones treatment

This work describes the impact of long term consumption of an isoflavone-rich dietary daily supplement on the composition and diversity of the faecal microbiota of a menopausal, equol-producing woman. Sequencing of 16S rDNA amplicons was performed on faecal samples taken at 0, 1, 3 and 6 months of treatment. Additionally, and for comparative purposes, ethidium monoazide (EMA) was used to avoid detection of DNA from dead bacteria. Members of two genera of the family Coriobacteriaceae (<em>Eggerthella</em> and <em>Collinsella</em>) were found in greater proportions at all sampling points during isoflavone supplementation. Different genera of the family Ruminococcaceae (e.g., <em>Ruminococcus</em> and <em>Faecalibacterium</em>), as well as members of the family Lachnospiraceae (<em>Coprococcus</em>) also underwent significant increases. For this last genus a positive correlation with the levels of equol excretion in urine was found. Currently bacterial strains known to be involved in isoflavone metabolism and equol production have been assigned to these taxa. The use of EMA dye allowed us to unravel those bacterial gut linages (e.g., Lachnospiraceae) that were more susceptible to damage. Our study contributes to the identification of microorganisms possibly involved in the production of isoflavone-desirable metabolites (such as equol), which could ultimately be isolated and further used as probiotics by people who cannot naturally benefit from isoflavones.

Bioavailability of isoflavones from soy products in equol producers and non-producers in Japanese women

BackgroundThe estimated intake of soy isoflavones from a meal has been based on the content in a food, but the health effects of soy isoflavones are possibly affected by their bioavailability. In this study we have evaluated the isoflavone bioavailability after the intake of three kinds of soy foods and a commercial soy isoflavone supplement, and examined whether the isoflavone bioavailability is different between equol producers and non-producers. MethodsHealthy female subjects (n = 20; 9 equol producers, 11 equol non-producers) aged between 20 and 26 y participated in this study. To assess the bioavailability of isoflavones, equol producers and non-producers consumed three kinds of soy foods (tofu, fermented soybeans: natto in Japanese, soy milk) and a soy isoflavone supplement containing 75 mg isoflavones together with breakfast. Urine was collected for 24 h, and the amounts of urinary excretions of daidzein, genistein, and the metabolite equol were measured. The intra- and inter-individual variations in the bioavailability of isoflavones were also examined. ResultsThe bioavailability of daidzein following the consumption of tofu, natto, soy milk, and soy isoflavone supplement were 66.9%, 45.2%, 65.7%, and 57.9%, respectively, and the bioavailability of genistein following the consumption of these soy products were 33.7%, 24.4%, 31.2%, and 17.7%, respectively. The bioavailability of daidzein and genistein was significantly greater in equol non-producers than equol producers, especially following the consumption of soymilk. In the equol producers, the 24 h urinary excretion of equol was significantly greater after the intake of soy isoflavone supplement than after the intake of natto or soymilk. The analysis of relative reliability of intra- and inter-individual variations suggested that bioavailability of isoflavones is less variable following soymilk intake than soy isoflavone supplement. ConclusionsThe results in this study suggest that bioavailability of isoflavones are different between equol producers and non-producers, because the 24 h urinary excretion of equol in the equol producers were significantly lower than those in the equol non-producers.

Individual difference in faecal and urine equol excretion and their correlation with intestinal microbiota in large white sows

Equol is an end metabolite of daidzein produced by the intestinal microbiota, exhibiting stronger antioxidant and estrogenic activities. It has been proposed that the beneficial effects of soybean/phytoestrogens may be dependent on the intestinal equol-producing ability, i.e. the equol hypothesis. The ‘equol hypothesis’ has been well applied to human clinical studies. However, the information of equol-producing ability in sows is quite limited. In this study, the individual differences and correlation between equol excretion and intestinal microbiota in large white sows were assayed. The results showed faecal equol levels of 0.14–17.85 μg/g (coefficient of variation: 61.22%) and urinary equol levels of 0.53–8.19 μg/mL (coefficient of variation: 54.72%). The levels of equol and daidzein correlated positively in both urine and faeces (P &lt; 0.05). The levels of daidzein and ratio of equol : daidzein in both faeces and urine were significantly higher than equol status (P &lt; 0.01). Cluster analysis of denatured gradient gel electrophoresis patterns showed that faecal samples with similar equol concentrations had similar microbial composition. The Shannon diversity and bands number in gel was significant negatively correlative with faecal equol status (P &lt; 0.001). The population of total bacteria, Firmicutes and Bacteroidetes correlated negatively with faecal equol production (P &lt; 0.05). Positive correlations were found between urinary equol production and the population of bacteroidetes and methanogen-producing bacteria (P &lt; 0.05), demonstrating for the first time the relationship between equol excretions and gut interspecies H2 transfer in sows.

A cross-sectional study of equol producer status and self-reported vasomotor symptoms.

This study aims to evaluate the associations of vasomotor symptom (VMS) frequency, bother, and severity with equol producer status and dietary daidzein intake. This is an observational study. This study included women aged 45 to 55 years, in postmenopause or in the menopausal transition, who had soy food intake of three or more servings per week. Exclusion criteria included severe concurrent disease, pregnancy or planned pregnancy, and current use of oral or transdermal hormones or selective estrogen receptor modulators. After screening, 375 participants completed a 3-day VMS diary and a 24-hour urine collection. Women with a urine daidzein or genistein concentration of 100 ng/mL or higher were included. We evaluated the association of VMS--dichotomized as lower than or equal to versus higher than the mean number of VMS per day (<2.33, ≥ 2.33)--with quartiles of daidzein intake. Overall, 129 (35%) of 365 women were equol producers. The mean (SD) urinary equol excretion was 0.67 (1.57) mg/day (50th percentile, 0 mg/d; 95th percentile, 4.12 mg/d). Among equol producers, the mean (SD) urinary equol excretion was 1.91 (2.15) mg/day (50th percentile, 1.09 mg/d; 95th percentile, 6.27 mg/d). Among equol producers, compared with those in the lowest quartile of dietary daidzein intake (mean, 4.9 mg/d), those in the highest quartile (mean, 28.5 mg/d) were 76% less likely to have VMS higher than the mean number of VMS (odds ratio, 0.24; 95% CI, 0.07-0.83; trend test across all daidzein levels, P = 0.06). Among equol nonproducers, there were no associations between daidzein intake and VMS frequency. There were no differences in VMS bother or severity among equol producers or nonproducers by dietary daidzein level. Among equol producers, higher equol availability attributable to higher soy consumption contributes to decreased VMS.

Inter- and intra-individual variation in urinary excretion of daidzein and equol in female Japanese

Objective: To evaluate the representativeness of single measurement of urinary soy-isoflavone concentrations for the assessment of long-term intake levels.Methods: Five urine samples taken from 14 Japanese female subjects over 2–3 months were measured for daidzein and equol by gas chromatography-mass spectrometry (GC-MS).Results: Geometric mean daidzein and equol concentrations of 14 subjects were 582 and 2.66 μg/g creatinine, respectively. Intra-class correlation coefficients for daidzein and equol were 0.355 (95% CI: 0.130–0.649) and 0.741 (0.551–0.891), respectively.Conclusion: Single measurement of urinary equol is effective for the assessment of long-term equol status of Japanese subject while that of daidzein is not.

Distribution of 24-h urinary equol excretion as an indicator of the physiological range in healthy Japanese equol excretors

Equol is produced from daidzein, a soy isoflavone, through metabolism by intestinal bacteria, and benefits health. This cross-sectional study aimed to investigate its physiological range, using 24h urinary equol excretion as an indicator, in Japanese people who consume soybeans in their usual diet. The 24h urine of 1345 subjects (545 men and 800 women) was collected, and equol, daidzein, and genistein concentrations were measured. Subjects with detectable equol in their urine (⩾0.27nmol/ml) were considered equol excretors. Among men, 36.3% were equol excretors; among women, 40.8%. The rate of equol excretors and urinary equol excretion differed significantly by age, but not by gender. In all equol excretors, the range of 24h urinary equol excretion was 0.4–318.0μmol/day; the median was 12.5μmol/day; and the 95th percentile was 119.2μmol/day. This range appears to be the physiological range of equol excretion in Japanese people who consume soy food regularly.

Urinary isoflavonoids and risk of coronary heart disease.

Whether soy food consumption may protect against coronary heart disease (CHD) remains controversial. No previous study has used biomarkers of soy intake in assessing the relationship between soy consumption and CHD. Biomarkers that reflect both intake and metabolism may be more informative than self-reports of dietary intake. We examined associations of urinary isoflavonoids, a biomarker of soy or soy isoflavone intake, with risk of CHD in a case-control study nested within two prospective cohort studies of Chinese adults in Shanghai. Cases were defined as subjects with no history of CHD at baseline who developed incident CHD during follow-up. Control subjects were randomly selected from those who remained free of CHD and matched to cases by sex, age, date and time of sample collection and antibiotic use. Baseline urinary isoflavonoids (daidzein, genistein, glycitein, equol, O-desmethylangolensin, dihydrodaidzein and dihydrogenistein) were compared between cases (n = 377) and control subjects (n = 753). Conditional logistic regression was used to evaluate the associations. Total urinary isoflavonoids were not associated with CHD in either women or men. However, urinary equol excretion showed a significant inverse association with CHD in women. The adjusted odds ratios (95% confidence intervals) for CHD across increasing quartiles of equol levels in women were 1 (reference), 0.61 (0.32, 1.15), 0.51 (0.26, 0.98) and 0.46 (0.24, 0.89) (P = 0.02 for trend). Our study suggests for the first time that equol, a bioactive metabolite of soy isoflavone daidzein, may be inversely associated with risk of CHD in women.

Soya isoflavone consumption in relation to carotid intima–media thickness in Chinese equol excretors aged 40–65 years

Previous studies have suggested that the daidzein metabolite equol rather than daidzein itself contributes to the beneficial effect of soya foods in the prevention of CVD. The aim of the present study is to examine the proportion of equol excretion in Chinese adults and compare plasma lipids and carotid artery intima-media thickness (IMT) between equol excretors and non-excretors, and to evaluate the effect of soya isoflavone intakes on serum lipids and IMT in either equol excretors or non-excretors. Subjects (n 572; women n 362, men n 210) were recruited for the present study. An overnight urine sample was provided by each subject on their usual diet to quantify urinary concentrations of daidzein and equol. Far-wall IMT was determined by B-mode ultrasound in the right carotid at two sites, carotid bulb (CB-IMT) and common carotid artery (CCA-IMT), and fasting serum lipids were measured. Habitual dietary intakes were estimated with a FFQ, and soya isoflavone intake derived from the FFQ was assessed. Of the 572 subjects, the proportion of equol excretors on their usual diet was 25·0 % (n 143). Compared with non-excretors, equol excretors showed significantly lower serum TAG (-38·2 (95 % CI -70·4, -5·9) %, P = 0·012) and CCA-IMT (-4·9 (95 % CI -9·7, -0·3) %, P = 0·033). Equol excretors with higher daily isoflavone intakes (-5·4 mg/d) had significantly lower IMT (-16·2 %, P = 0·035) and tended to have higher HDL-cholesterol (P = 0·055) than did those with lower daily isoflavone intakes (1·5 mg/d), while no association was observed between soya isoflavone intakes and serum lipids or IMT in non-excretors. In conclusion, the benefits of soya isoflavones in preventing CVD may be apparent among equol excretors only.

GC‐MS Determined Distribution of Urinary Equol Producers as Affected by Age, Gender, and Repeated Ingestions of Soymilk

Status of equol excretion is likely a reflection of incidence risk of sex-hormone related diseases and deserves research attention. In this study, urine samples collected from 182 volunteers after soymilk ingestion were subjected to equol quantification using GC-MS. As categorized into male, female, and both genders and each category further classified into 6 age (year) categories, namely, <20, 21 to 30, 31 to 40, 41 to 50, >51 and overall, a trend indicating that the younger age the higher equol producer ratio was observed. For the >51 subjects, the corresponding producer ratios of males and females were 35.3% and 50.0%, respectively. Among the volunteers, 20 nonproducers were further recruited to ingest 1000 mL soymilk weekly for 16 wk and urines were analyzed bi-weekly. As resulted, 8 of 20 nonproducers were induced to become equol producers. The observed change of nonproducers to equol producers induced by repeating ingestions of soymilk is of merit from the viewpoint of healthcare.

Urinary isoflavone phytoestrogens in German children and adolescents – A longitudinal examination in the DONALD cohort

In light of concerns about hormonally active agents, it is important to assess human exposure to such compounds, especially in children as a susceptible subgroup. Estrogenic plant constituents are present in the human diet in varying levels, in particular the isoflavones daidzein (DAI) and genistein (GEN). We aimed to examine age-dependent and secular trends in phytoestrogen exposures and to investigate equol (EQ) excretion of German children using biomarker analysis in 24-h urine samples from a longitudinally designed study. The concentrations of DAI, its metabolite EQ and GEN were determined by GC-MS analysis in 24-h urines (510 samples) collected between 1985 and 2000 in 90 (47 boys) German children (6-18 years old), who are participants in the Dortmund Nutritional and Anthropometric Longitudinally Designed study. The results from the urinary biomarker analysis indicate isoflavone exposures at quite variable levels in German children: Analyte concentrations in over 500 urine samples cover the range reported previously in adults on typical German diet and with soy intake. EQ, the DAI metabolite produced by the gastrointestinal microflora, was detected in a high fraction of all samples, with 28/90 children (31%) excreting EQ in all their urines, and 62/90 children (68%) in at least one sample. Interestingly, when multiple urines obtained from individuals at different ages (6-18 years) were analyzed, EQ formation did not appear to be a constant trait over time. When stratified by sex, DAI, EQ and GEN concentrations (ng/mL) in urines and excretion rates (μg/day) were similar in boys and girls. Total isoflavone excretion rates (μg/day) increased during childhood (6-12 years) (p=0.02) and were constant during adolescence (13-18 years) (p=0.6). No clear trend for changes in dietary isoflavone exposure over the total study period was seen (p=0.7). In conclusion, biomarkers in urine of German children and adolescents indicate a frequent, but widely variable dietary isoflavone intake and suggest no secular increase (1985-2000) in the exposure to isoflavone phytoestrogens among German children and adolescents.

Effect of diet on fecal and urinary estrogenic activity

The United States Environmental Protection Agency has identified estrogens from animal feeding operations as a major environmental concern, but few data are available to quantify the excretion of estrogenic compounds by dairy cattle. The objectives of this study were to quantify variation in estrogenic activity in feces and urine due to increased dietary inclusion of phytoestrogens. Ten Holstein heifers were assigned to 2 groups balanced for age and days pregnant; groups were randomly assigned to treatment sequence in a 2-period crossover design. Dietary treatments consisted of grass hay or red clover hay, and necessary supplements. Total collection allowed for sampling of feed refusals, feces, and urine during the last 4 d of each period. Feces and urine samples were pooled by heifer and period, and base extracts were analyzed for estrogenic activity (estrogen equivalents) using the yeast estrogen screen bioassay. Feces and urine samples collected from 5 heifers were extracted and analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) to quantify excretion of 7 phytoestrogenic compounds. Excretion of 17-β estradiol equivalents in urine was higher and tended to be higher in feces for heifers fed red clover hay (84.4 and 120.2 mg/d for feces and urine, respectively) compared with those fed grass hay (57.4 and 35.6 mg/d). Analysis by LC-MS/MS indicated greater fecal excretion of equol, genistein, daidzein, coumestrol, and formononetin by heifers fed red clover hay (1634, 29.9, 96.3, 27.8, and 163 mg/d, respectively) than heifers fed grass hay (340, 3.0, 46.2, 8.8, and 18.3 mg/d, respectively). Diet had no effect on fecal biochanin A or 2-carbethoxy-5, 7-dihydroxy-4’-methoxyisoflavone. Four phytoestrogens were detected in urine (2-carbethoxy-5, 7-dihydroxy-4’-methoxyisoflavone, daidzein, equol, and formononetin) and their excretion was not affected by diet. Identifying sources of variation in estrogenic activity of manure will aid in the development of practices to reduce environmental estrogen accumulation.

Prevalence of the Equol-Producer Phenotype and Its Relationship with Dietary Isoflavone and Serum Lipids in Healthy Chinese Adults

BackgroundStudies have suggested that daidzein-metabolizing phenotypes have beneficial effects on a range of health outcomes. We investigated the prevalence of equol producers and the relationship of equol phenotype with habitual isoflavone consumption and serum lipid concentrations in 200 Chinese adults in Beijing.MethodsAfter the baseline survey and dietary records, 200 healthy adults in Beijing were challenged with a soy-isoflavone supplement for 3 days; 24-hour urine samples were collected before and after the challenge. Isoflavones and their metabolites in urine were measured to determine equol phenotype. Serum lipids, uric acid, and other biochemical markers were also measured.ResultsOnly 26.8% of the participants excreted equol when on a regular diet, as compared with 60.4% after the challenge. After the challenge, urinary isoflavonoid excretion increased in all participants, while equol excretion increased only in equol producers. Isoflavone intake was correlated with urinary isoflavone (range r = 0.49–0.58, P < 0.01). As compared with nonproducers, equol producers were less likely to consume cereals (P < 0.001). There was no significant correlation between serum lipids and isoflavone intake. Serum lipids were not significantly affected by equol phenotype.ConclusionsUrinary equol excretion was detected in about 25% of participants under their usual dietary conditions. Their potential to produce equol was increased after the challenge. Urinary isoflavone levels may serve as a useful biomarker for isoflavone intake in populations. We observed an association between equol phenotype and cereal intake. Our findings also suggest that dietary isoflavone intake has no significant effect on serum lipids in healthy participants, regardless of equol phenotype.

Urinary phytoestrogen excretion and postmenopausal breast cancer risk: the multiethnic cohort study.

The objective of this study was to examine the association of urinary phytoestrogens with the risk of postmenopausal breast cancer. Participants in the Multiethnic Cohort Study included 36,458 postmenopausal women who provided blood or urine specimens. A nested case-control study of breast cancer with biospecimens was created in which cases diagnosed after specimen collection were matched to two controls. Two hundred fifty-one women with breast cancer and 462 controls had urine available for analysis of urinary phytoestrogens. Odds ratios (OR) and 95% confidence intervals (CI) were obtained using conditional logistic regression. A nonmonotonic inverse trend (P = 0.04) in breast cancer risk was associated with increasing urinary excretion of genistein (OR 25th-75th percentile, 0.88; 95% CI, 0.78-0.99) and total isoflavones (OR 25th-75th percentile, 0.80; 95% CI, 0.65-0.99). A significant reduction in breast cancer risk in Japanese-American women was associated with the highest compared with the lowest quartile excretion of urinary daidzein (OR, 0.41; 95% CI, 0.19-0.89; P(trend), 0.005). The risk of breast cancer was reduced among White women with the highest compared with the lowest quartile excretion of equol (OR, 0.27; 95% CI, 0.08-0.95), although the trend in risk was not significant (P = 0.07). Our results provide some support to the hypothesis that a diet rich in isoflavones from soy products reduces the risk of postmenopausal breast cancer, particularly in populations with comparatively high excretion of phytoestrogens.

Soya protein does not affect glycaemic control in adults with type 2 diabetes

Evidence from observational, animal and human studies supports a role for soya protein and its isoflavones in the improvement of glycaemic control in type 2 diabetes. The objective of the present study was to determine the effect of isoflavone-rich soya protein on markers of glycaemic control in adults with type 2 diabetes. Using a randomised, crossover, double-blind, placebo-controlled design, adults with diet-controlled type 2 diabetes (n 29) consumed soya protein isolate (SPI) and milk protein isolate (MPI) for 57 d each separated by a 4-week washout. Blood was collected on days 1 and 57 of each treatment period for analysis of fasting HbA1C, and fasting and postprandial glucose, insulin and calculated indices of insulin sensitivity and resistance. Urine samples of 24 h were collected at the end of each treatment period for analysis of isoflavones. Urinary isoflavone excretion was significantly greater following consumption of SPI compared with MPI, and 20.7 % of the subjects (n 6) were classified as equol excretors. SPI consumption did not significantly affect fasting or postprandial glucose or insulin, fasting HbA1C, or indices of insulin sensitivity and resistance. These data do not support a role for soya protein in the improvement of glycaemic control in adults with diet-controlled type 2 diabetes and contribute to a limited literature of human studies on the effects of soya protein on the management of type 2 diabetes.

Urinary phytoestrogen excretion and prostate cancer risk: a nested case–control study in the Multiethnic Cohort

Background:Phytoestrogens are of special interest in prostate cancer research because populations in Asia with a high consumption of phytoestrogens have a lower incidence of the disease than comparable populations in Western countries.Methods:This case–control study is nested within a large multiethnic cohort in Hawaii and California. Urine samples were analysed for daidzein, genistein, equol, and enterolactone among 249 incident prostate cancer cases and 404 controls matched on age, race/ethnicity, date/time of specimen collection, and fasting status.Results:The median excretion of daidzein was 0.173 nmol mg−1 creatinine in cases and 0.291 in controls (P=0.01), and the median excretion of genistein was 0.048 in cases and 0.078 in controls (P=0.05). An inverse association was seen for daidzein overall (odds ratio for the highest vs lowest quintile=0.55, 95% confidence interval=0.31–0.98, Ptrend=0.03) and seemed to apply to localized (Ptrend=0.08) as well as advanced or high-grade cancer (Ptrend=0.09). This association was consistent across the four ethnic groups examined. Although the relationship was weaker for genistein, the odds ratios and trends were similarly inverse. Urinary excretion of equol and enterolactone was not significantly related to prostate cancer risk.Conclusion:Our findings suggest that high intake of isoflavones, as reflected by urinary excretion of daidzein and genistein, may be protective against prostate cancer.

The effect of feeding soybean-derived phytoestogens on their concentration in plasma and milk of lactating dairy cows

The objective of this study was to determine the effect of dietary soybean phytoestrogens, daidzein and genistein, on yield and composition of milk and excretion of phytoestrogens and their metabolites into milk. The experiment was carried out on four lactating Holstein cows as replicated Latin square in a double reversal design. The experiment was divided into four periods of 42 days consisting of a 21-day preliminary period and a 21-day experimental period. Cows were divided into two groups. The control group (Group R) was fed a diet based on extruded rapeseed cake while the experimental group (Group S) received a diet containing extruded full-fat soybeans. Compared to Group R, in Group S the daily intake of daidzein and genistein was about 40 and 75 times higher, respectively. In the milk of Group S the concentration of daidzein and its metabolite equol was significantly higher (p < 0.001) and the concentration of genistein tended to be higher than in Group R. Total excretion of daidzein, genistein and equol in milk of Group S, being 384, 958 and 1300 μg/d, respectively, was higher than in Group R (285, 794 and 80 μg/d, respectively, p < 0.001). In Group S the concentration of daidzein, genistein and equol in plasma was also increased (p < 0.001).