Equol production changes over time in postmenopausal women

Comparison of the five different definitions of equol producers: The relationship between blood and urine equol concentrations and blood parameters in 466 healthy men and women

BACKGROUND AND AIMS

No studies have compared various definitions of "equol producers" until now. Therefore, we aimed to explore the accuracy of five different definitions of equol producers (EQP) and their associations with health benefits.

METHODS

This is a cross-sectional study of 466 healthy Japanese men and women aged between 22 and 88 years. Equol producer proportions were calculated from their serum and urine isoflavone concentrations using five commonly used definitions. We then examined their accuracy, and associations with the blood parameters.

RESULTS

Proportions of equol ranged from 29 % in the most stringent definition to 47.6 % in the most sensitive definition. EQP identified under all definitions had significantly low serum PSA1 levels compared to nonequol producers (NEQP). The most stringent definition, which is defined as the urinary equol level of 1.0 μM and above, corresponded to the highest median serum equol level and was associated with better health outcomes. Male EQP identified by this definition seemed to have reduced risk of LDL2-hypercholesterolemia by 50 %, and female EQP identified by this definition seemed to have lower risk of high hs-CRP,3 compared to NEQP. Both the first and second stringent definition, which is defined as the serum equol level of 1.0 ng/mL and above, was associated with lower thyroid stimulating hormone level.

CONCLUSIONS

More stringent definitions were associated with better parameters in general. Combined with the dietary inquires, a reliable definition for equol producer is crucial to evaluate the health benefits of equol.

Effect of soy isoflavones on C-reactive protein in chronic inflammatory disorders

New evidence suggests that soy products might reduce chronic systemic inflammation. Therefore, we aimed to summarize the effect of soy isoflavones on serum concentration of C-reactive protein (CRP) among participants with chronic inflammatory disorders by conducting this study. Cochrane Library, Scopus, ISI Web of Science, clinicaltrials.gov, and PubMed were searched to identify randomized clinical trials (RCTs) published up to December 2020. The effect size was calculated by the mean change from baseline in concentrations of CRP and its standard deviation for both intervention and comparison groups. DerSimonian and Laird random-effects model was used when the heterogeneity test was statistically significant. In total, thirteen RCTs involving 1213 participants and ten RCTs involving 1052 participants were eligible for our systematic review and meta-analysis respectively. Study duration ranged from 4 to 96 weeks and soy isoflavones dose varied from 33 to 132 mg/day. Overall effect size indicated a non-significant effect on serum concentration of CRP following soy isoflavones intake (weighted mean differences (WMD)=-0.15 mg/L, 95% confidence interval (CI): -0.54, 0.23; p=0.430). Subgroup analysis revealed that soy isoflavones significantly reduced serum concentration of CRP in studies among participants with age >57 years and baseline CRP levels >3.75 mg/L. The present study proposed that soy isoflavones could not significantly reduce serum CRP levels. It seems more RCTs on participants with age more than 57 years and higher levels of CRP is necessary.

Potential Protective Mechanisms of S-equol, a Metabolite of Soy Isoflavone by the Gut Microbiome, on Cognitive Decline and Dementia

S-equol, a metabolite of soy isoflavone daidzein transformed by the gut microbiome, is the most biologically potent among all soy isoflavones and their metabolites. Soy isoflavones are phytoestrogens and exert their actions through estrogen receptor-β. Epidemiological studies in East Asia, where soy isoflavones are regularly consumed, show that dietary isoflavone intake is inversely associated with cognitive decline and dementia; however, randomized controlled trials of soy isoflavones in Western countries did not generally show their cognitive benefit. The discrepant results may be attributed to S-equol production capability; after consuming soy isoflavones, 40-70% of East Asians produce S-equol, whereas 20-30% of Westerners do. Recent observational and clinical studies in Japan show that S-equol but not soy isoflavones is inversely associated with multiple vascular pathologies, contributing to cognitive impairment and dementia, including arterial stiffness and white matter lesion volume. S-equol has better permeability to the blood-brain barrier than soy isoflavones, although their affinity to estrogen receptor-β is similar. S-equol is also the most potent antioxidant among all known soy isoflavones. Although S-equol is available as a dietary supplement, no long-term trials in humans have examined the effect of S-equol supplementation on arterial stiffness, cerebrovascular disease, cognitive decline, or dementia.

Maximizing the Estrogenic Potential of Soy Isoflavones through the Gut Microbiome: Implication for Cardiometabolic Health in Postmenopausal Women

Soy isoflavones have been suggested as an alternative treatment for managing postmenopausal symptoms and promoting long-term health due to their structural similarity to mammalian estrogen and ability to bind to estrogen receptors. Among all soy isoflavones and their metabolites, (S)-equol is known for having the strongest estrogenic activity. Equol is a metabolite of the soy isoflavone daidzein produced through intestinal bacterial metabolism. However, more than half of the human population is not able to produce equol due to the lack of equol-producing bacteria in their gastrointestinal tract. The interpersonal variations in the gut microbiome complicate the interpretation of data collected from humans. Furthermore, because rodents are efficient equol-producers, translatability between rodent models and humans is challenging. Herein, we first summarized the current knowledge of the microbial conversion of daidzein to equol, its relation to health, and proposed the need for developing model systems by which equol production can be manipulated while controlling other known confounding factors. Determining the necessity of equol-producing capacity within a gut microbial community when consuming soy as a functional ingredient, and identifying strategies to maximize equol production by modulating the gut microbiome, may provide future therapeutic approaches to improve the health of postmenopausal women.

Effects of an equol-containing supplement on advanced glycation end products, visceral fat and climacteric symptoms in postmenopausal women: A randomized controlled trial

INTRODUCTION

Equol, an isoflavone derivative whose chemical structure is similar to estrogen, is considered a potentially effective agent for relieving climacteric symptoms, for the prevention of lifestyle-related diseases, and for aging care in postmenopausal women. We investigated the effect of an equol-containing supplement on metabolism and aging and climacteric symptoms with respect to internally produced equol in postmenopausal women.

METHODS

A single-center, randomized controlled trial (registration number: UMIN000030975) on 57 postmenopausal Japanese women (mean age: 56±5.37 years) was conducted. Twenty-seven women received the equol supplement, while the remaining received control. Metabolic and aging-related biomarkers were compared before and after the 3-month intervention. Climacteric symptoms were assessed every month using a validated self-administered questionnaire in Japanese postmenopausal women.

RESULTS

Three months post-intervention, the treatment group showed significant improvement in climacteric symptoms compared to the control group (81% vs. 53%, respectively, p = 0.045). We did not observe any beneficial effect on metabolic and aging-related biomarkers in the intervention group. However, in certain populations, significant improvement in skin autofluorescence, which is a measurement of AGE skin products, and visceral fat area was observed, especially among equol producers.

CONCLUSION

Women receiving equol supplementation showed improved climacteric symptoms. This study offered a new hypothesis that there may be a synergy between supplemented equol and endogenously produced equol to improve skin aging and visceral fat in certain populations.

Effects of daidzein and genistein on markers of cardiovascular disease risk among women with impaired glucose regulation: a double-blind, randomized, placebo-controlled trial

BACKGROUND AND OBJECTIVE

soy protein and soy isoflavones have been suggested to be associated with improved cardiovascular risk factors (e.g., lipid profiles and uric acid (UA)), but few studies have been conducted among women with impaired glucose regulation (IGR). This study is aimed to evaluate the effect of isolated daidzein and genistein on lipid profiles, high sensitive C-reactive protein (hs-CRP), and uric acid (UA) among Chinese women with IGR.

METHODS AND RESULTS

this randomized, double-blind, and placebo-controlled trial was conducted in 165 Chinese women aged 30-70 years with IGR. Participants were randomly assigned to one of the three groups: 0 mg of daidzein and genistein with 10 g soy protein (placebo group), 50 mg of daidzein with 10 g soy protein (daidzein group), or 50 mg of genistein with 10 g soy protein (genistein group) supplementation for 24 weeks. Fasting serum total cholesterol (TC), triacylglycerol (TG), high-density lipoprotein (HDL-C), low-density lipoprotein (LDL-C), lipoprotein a (LP (a)), hs-CRP, and UA were assessed at baseline, 12, and 24 weeks after intervention. The results showed no significant differences in the changes (%) of TC, TG, HDL-C, LDL-C, LP (a), hs-CRP, and UA between the three treatment groups at weeks 12 or 24 (all P > 0.05).

CONCLUSION

neither isolated daidzein nor genistein had a significant effect on cardiovascular health in Chinese women with IGR.

Effects of soy intake on circulating levels of TNF-α and interleukin-6: a systematic review and meta-analysis of randomized controlled trials

PURPOSE

Pro-inflammatory mediators, including serum tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6), can be used as biomarkers to indicate or monitor disease. This study was designed to ascertain the effects of soy products on TNF-α and IL-6 levels.

METHODS

PubMed, EMBASE, Science Direct, Web of Science, Google Scholar and the Cochrane Central Register of Controlled Trials were searched to November 2019 for RCTs around the effects of soy-based products on TNF-α and IL-6. A random effects model was used to calculate overall effect size.

RESULTS

In total, 29 eligible publications were considered in the present systematic review, of which 25 were included in this meta-analysis. The overall effect of soy products on TNF-α and IL-6 levels failed to reach statistical significance (MD = - 0.07; 95% CI - 0.22-0.09; I² 50.9; MD = 0.03; 95% CI - 0.07-0.14; I² 42.1, respectively). According to a subgroup analysis, natural soy products led to a reduction in TNF-α concentration compared with processed soy products (MD = - 0.32; 95% CI - 0.45 to - 0.19; I² 0.0). Moreover, IL-6 reduction was stronger in participants who were affected by different diseases (MD = - 0.04; 95% CI - 0.07 to - 0.02; I² 0.0).

CONCLUSIONS

A review of RCTs published to November 2019 found that natural soy products are effective in lowering TNF-α levels. While the beneficial effects on reduction of IL-6 appeared stronger in individuals affected by different diseases, this finding cannot be generalized to all individuals affected by different diseases.

Inter-relationship between diet, lifestyle habits, gut microflora, and the equol-producer phenotype: baseline findings from a placebo-controlled intervention trial

OBJECTIVE

Equol is an active metabolite of isoflavones produced by gut microbiota. It is beneficial to health; however, equol-producing ability varies greatly among individuals. These variations depend on the host's gut microbiota and lifestyle habits including diet. We investigated the relationship between the gut microbiota, lifestyle habits including diet, and equol-producing ability in postmenopausal Japanese women.

METHODS

We studied 58 postmenopausal Japanese women aged 48 to 69 years who visited the Sendai Medical Center in January, 2018. Self-administered questionnaires assessed their recent and remote food intake histories and lifestyle habits. Fecal microbiome analysis was performed using a next-generation sequencer. Urinary equol was measured using an immunochromatographic strip test. Women with urinary equol concentration >1.0 μM were defined as equol producers.

RESULTS

Equol-producing bacteria were identified in 97% (56) of women; however, only 13 (22%) were equol producers. Equol producers showed significantly higher microflora diversity (P = 0.002), and significantly different recent and remote food intake patterns compared with equol nonproducers. Higher consumption of foods such as meat, fish, soy, vegetables, and Japanese snacks positively affected microbial diversity and equol production, whereas a high intake of Ramen and smoking showed negative effects.

CONCLUSION

Equol production might not depend on the quantity, but on the quality of equol-producing bacteria. High microbial diversity might enhance equol production. Increasing microbial diversity through healthy lifestyle habits and habitual consumption of a wide variety of foods might be useful to maintain a healthy gut environment for equol production.

Equol: A Bacterial Metabolite from The Daidzein Isoflavone and Its Presumed Beneficial Health Effects

Epidemiological data suggest that regular intake of isoflavones from soy reduces the incidence of estrogen-dependent and aging-associated disorders, such as menopause symptoms in women, osteoporosis, cardiovascular diseases and cancer. Equol, produced from daidzein, is the isoflavone-derived metabolite with the greatest estrogenic and antioxidant activity. Consequently, equol has been endorsed as having many beneficial effects on human health. The conversion of daidzein into equol takes place in the intestine via the action of reductase enzymes belonging to incompletely characterized members of the gut microbiota. While all animal species analyzed so far produce equol, only between one third and one half of human subjects (depending on the community) are able to do so, ostensibly those that harbor equol-producing microbes. Conceivably, these subjects might be the only ones who can fully benefit from soy or isoflavone consumption. This review summarizes current knowledge on the microorganisms involved in, the genetic background to, and the biochemical pathways of, equol biosynthesis. It also outlines the results of recent clinical trials and meta-analyses on the effects of equol on different areas of human health and discusses briefly its presumptive mode of action.

A systematic review and meta-analysis of the effects of soy on serum hs-CRP

BACKGROUND & AIM

The results of studies about the effect of soy products on serum highly sensitive C-reactive protein (hs-CRP) are inconsistent. The aim of this systematic review and meta-analysis of randomized clinical trials (RCTs) was to investigate the effect of soy products intake on serum hs-CRP concentration.

METHODS

We searched PubMed, EMBASE, Science Direct, ISI Web of Science, Google Scholar and Cochrane Central Register of Controlled Trials up to December 2016 without language restrictions. Random-effect model was used for quantitative data synthesis.

RESULTS

Thirty-six studies were included in our analyses. A meta-analysis revealed a non-significant reduction in serum hs-CRP concentrations following soy products consumption, -0.19 (mg/L) (95% CI: -0.49 to 0.09; I2 = 95.6%). Subgroup analyses suggested that natural soya products may reduce plasma levels of CRP by -0.18 mg/L (95% CI: -0.28 to -0.08; I2: 11.6) in comparison to other source of isoflavones (soya extracts, supplements). Moreover, the effect was stronger among subjects with baseline hs-CRP concentrations of less than 2.52 mg/L, -0.15 (95% CI: -0.27 to -0.02; I2: 34.6). A meta-regression analysis revealed that dosage of isoflavones seems to be a strong predictor of the effect of soya on serum hs-CRP levels.

CONCLUSION

Present review of RCTs published up to December 2016 did not provide strong evidence regarding the beneficial effect of soya products consumption on blood hs-CRP concentrations. However, it appears that natural soya products may reduce plasma levels of hs-CRP in comparison to other source of isoflavones. Large and well-designed studies are recommended to confirm this conclusion.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42018069371.

Isoflavones

Phytoestrogens are naturally occurring nonsteroidal phenolic plant compounds that, due to their molecular structure and size, resemble vertebrate steroids estrogens. This review is focused on plant flavonoids isoflavones, which are ranked among the most estrogenic compounds. The main dietary sources of isoflavones for humans are soybean and soybean products, which contain mainly daidzein and genistein. When they are consumed, they exert estrogenic and/or antiestrogenic effects. Isoflavones are considered chemoprotective and can be used as an alternative therapy for a wide range of hormonal disorders, including several cancer types, namely breast cancer and prostate cancer, cardiovascular diseases, osteoporosis, or menopausal symptoms. On the other hand, isoflavones may also be considered endocrine disruptors with possible negative influences on the state of health in a certain part of the population or on the environment. This review deals with isoflavone classification, structure, and occurrence, with their metabolism, biological, and health effects in humans and animals, and with their utilization and potential risks.

Biomarkers of legume intake in human intervention and observational studies: a systematic review

There is a growing interest in assessing dietary intake more accurately across different population groups, and biomarkers have emerged as a complementary tool to replace traditional dietary assessment methods. The purpose of this study was to conduct a systematic review of the literature available and evaluate the applicability and validity of biomarkers of legume intake reported across various observational and intervention studies. A systematic search in PubMed, Scopus, and ISI Web of Knowledge identified 44 studies which met the inclusion criteria for the review. Results from observational studies focused on soy or soy-based foods and demonstrated positive correlations between soy intake and urinary, plasma or serum isoflavonoid levels in different population groups. Similarly, intervention studies demonstrated increased genistein and daidzein levels in urine and plasma following soy intake. Both genistein and daidzein exhibited dose-response relationships. Other isoflavonoid levels such as O-desmethylangolensin (O-DMA) and equol were also reported to increase following soy consumption. Using a developed scoring system, genistein and daidzein can be considered as promising candidate markers for soy consumption. Furthermore, genistein and daidzein also served as good estimates of soy intake as evidenced from long-term exposure studies marking their status as validated biomarkers. On the contrary, only few studies indicated proposed biomarkers for pulses intake, with pipecolic acid and S-methylcysteine reported as markers reflecting dry bean consumption, unsaturated aliphatic, hydroxyl-dicarboxylic acid related to green beans intake and trigonelline reported as marker of peas consumption. However, data regarding criteria such as specificity, dose-response and time-response relationship, reliability, and feasibility to evaluate the validity of these markers is lacking. In conclusion, despite many studies suggesting proposed biomarkers for soy, there is a lack of information on markers of other different subtypes of legumes. Further discovery and validation studies are needed in order to identify reliable biomarkers of legume intake.

Optimal cut-off value for equol-producing status in women: The Japan Nurses' Health Study urinary isoflavone concentration survey

Equol is one of the most active soy isoflavones. When the association between soy food intake in daily life and health outcomes is examined in epidemiological studies, it is important to define the equol-producing status of each individual. However, few studies have assessed equol-producing status without a soy challenge test. To determine a robust cutoff criterion for equol producer classification in observational studies, we conducted a urinary isoflavone concentration survey in daily life among women. Furthermore, we examined the association between eating habits regarding soy foods and equol-producing status. A total of 4,412 participants were included in the analyses. Urinary isoflavones were analyzed using a high-performance liquid chromatography method. We examined the distribution of the log₁₀ equol/daidzein ratios, finding a mixture of two normal distributions, corresponding to equol producer and non-producer subpopulations. Applying a finite mixture model, we estimated the means, standard deviations, and mixing proportions of these two distributions. The estimation was carried out using the SAS NLIN procedure. The optimal cutoff point for the log₁₀ equol/daidzein ratio in the study population was determined to be −1.42, according to the estimated parameters of the mixture distribution. Based on this criterion, 1,830 (41.5%) of the participants were identified as equol producers. Compared with non-consumers of soy foods, consumers of soy foods had significantly higher odds of being equol producers. Using log₁₀-transformed equol/daidzein ratios ≥ −1.42 to define equol producers among Japanese women is reasonable and suitable for determining equol-producing status in epidemiological studies. We found that soy food eating habits were associated with equol-producing status. Further investigation is required to evaluate associations between equol-producing status in daily life and health outcomes. The results of this study suggest the best cutoff point to use in the definition of equol-producing status in daily life.

Effects of Equol Supplement on Bone and Cardiovascular Parameters in Middle-Aged Japanese Women: A Prospective Observational Study

Objective: To examine changes in the bone and cardiovascular parameters and tolerability in middle-aged Japanese women taking equol supplement for a year.

Design: This was a prospective observational study.

Subjects and Setting: Participants were 74 women receiving outpatient care at Hamasite Medical Clinic, Minato-ku, Tokyo, from 2013 to 2015.

Interventions: Participants received per oral equol-containing supplement, 10 mg/day.

Outcome measures: The primary outcome measures were percent changes in bone and cardiovascular parameters after 1 year supplementation with equol. The secondary measures included factors affecting the parameter changes and adverse effects associated with equol use for a year.

Results: Reduction in arterial stiffness was observed after 12 months of equol supplement (1402.3 cm/s vs.1367.3 cm/s, p < 0.001). Significant reductions in respective parameters were observed in women with moderate and high risk for arteriosclerosis (median [95% confidence interval]: −3.2% [−5.79 to −0.74]; −12.65% [−18.52 to −4.28]; respectively); hypertriglyceridemia −45.53% [−70.24 to −5.58]; bone resorption risk (−15.15% [−23.71 to 1.56]; and bone fracture risk −26.68% [−76.43 to −5.99]. All 15 women with high baseline parathyroid hormone levels had achieved a median of 50% [−54.11 to −31.69] reduction from their baseline values. These associations were further confirmed in the results of multiple linear regression analysis. There were no reported adverse events or abnormal findings in the blood chemistry, Pap smear, mammography, and transvaginal ultrasound during periodic follow-ups.

Conclusion: One year equol supplement was tolerable and induced improvement of certain bone and cardiovascular parameters, especially in higher risk groups. Further controlled studies are needed to explore long-term equol use for wellbeing of middle-aged women.

The history and basic science development of soy isoflavones

This review summarizes the 2016 NAMS/Pfizer-Wulf H. Utian Endowed Lecture that focused on the history and basic science of soy isoflavones. Described is a personal perspective of the background and history that led to the current interest in soy and isoflavones with a specific focus on the role that soy isoflavones play in the health of postmenopausal women. This overview covers the metabolism and physiological behavior of isoflavones, their biological properties that are of potential relevance to aging, issues related to the safety of soy isoflavones, and the role of the important intestinally derived metabolite S-(-)equol.

Combined bioavailable isoflavones and probiotics improve bone status and estrogen metabolism in postmenopausal osteopenic women: a randomized controlled trial

Background: Female age-related estrogen deficiency increases the risk of osteoporosis, which can be effectively treated with the use of hormone replacement therapy. However, hormone replacement therapy is demonstrated to increase cancer risk. Bioavailable isoflavones with selective estrogen receptor affinity show potential to prevent and treat osteoporosis while minimizing or eliminating carcinogenic side effects.Objective: In this study, we sought to determine the beneficial effects of a bioavailable isoflavone and probiotic treatment against postmenopausal osteopenia.Design: We used a novel red clover extract (RCE) rich in isoflavone aglycones and probiotics to concomitantly promote uptake and a favorable intestinal bacterial profile to enhance isoflavone bioavailability. This was a 12-mo, double-blind, parallel design, placebo-controlled, randomized controlled trial of 78 postmenopausal osteopenic women supplemented with calcium (1200 mg/d), magnesium (550 mg/d), and calcitriol (25 μg/d) given either RCE (60 mg isoflavone aglycones/d and probiotics) or a masked placebo [control (CON)].Results: RCE significantly attenuated bone mineral density (BMD) loss at the L2-L4 lumbar spine vertebra (P < 0.05), femoral neck (P < 0.01), and trochanter (P < 0.01) compared with CON (-0.99% and -2.2%; -1.04% and -3.05%; and -0.67% and -2.79, respectively). Plasma concentrations of collagen type 1 cross-linked C-telopeptide was significantly decreased in the RCE group (P < 0.05) compared with CON (-9.40% and -6.76%, respectively). RCE significantly elevated the plasma isoflavone concentration (P < 0.05), the urinary 2-hydroxyestrone (2-OH) to 16α-hydroxyestrone (16α-OH) ratio (P < 0.05), and equol-producer status (P < 0.05) compared with CON. RCE had no significant effect on other bone turnover biomarkers. Self-reported diet and physical activity were consistent and differences were nonsignificant between groups throughout the study. RCE was well tolerated with no adverse events.Conclusions: Twice daily RCE intake over 1 y potently attenuated BMD loss caused by estrogen deficiency, improved bone turnover, promoted a favorable estrogen metabolite profile (2-OH:16α-OH), and stimulated equol production in postmenopausal women with osteopenia. RCE intake combined with supplementation (calcium, magnesium, and calcitriol) was more effective than supplementation alone. This trial was registered at clinicaltrials.gov as NCT02174666.

Addressing the inter-individual variation in response to consumption of plant food bioactives: Towards a better understanding of their role in healthy aging and cardiometabolic risk reduction

Bioactive compounds in plant-based foods have health properties that contribute to the prevention of age-related chronic diseases, particularly cardiometabolic disorders. Conclusive proof and understanding of these benefits in humans is essential in order to provide effective dietary recommendations but, so far, the evidence obtained from human intervention trials is limited and contradictory. This is partly due to differences between individuals in the absorption, distribution, metabolism and excretion of bioactive compounds, as well as to heterogeneity in their biological response regarding cardiometabolic health outcomes. Identifying the main factors underlying inter-individual differences, as well as developing new and innovative methodologies to account for such variability constitute an overarching goal to ultimately optimize the beneficial health effects of plant food bioactives for each and every one of us. In this respect, this position paper from the COST Action FA1403-POSITIVe examines the main factors likely to affect the individual responses to consumption of plant food bioactives and presents perspectives for assessment and consideration of inter-individual variability.

Being overweight or obese is associated with harboring a gut microbial community not capable of metabolizing the soy isoflavone daidzein to O-desmethylangolensin in peri- and post-menopausal women

OBJECTIVE

Obesity can be a considerable health concern for peri- and post-menopausal women. Evidence suggests an association between the gut microbiome and obesity. The study objective was to evaluate the association between being overweight or obese and phenotypic markers of having an overall gut microbial environment not capable of metabolizing the isoflavone daidzein to equol or O-desmethylangolensin (ODMA).

STUDY DESIGN

Cross-sectional study of 137 peri- and 218 post-menopausal women, aged 44-55 years, who consumed at least three servings per week of soy (source of daidzein). Equol and ODMA producers and non-producers were identified based on urinary concentrations of daidzein, equol and ODMA in a 24-h urine sample.

MAIN OUTCOME MEASURES

Mean body mass index (BMI) and odds of obesity.

RESULTS

Fifty-one women were ODMA non-producers and 226 were equol non-producers. The ODMA non-producer phenotype was positively associated with obesity (OR: 3.33, 95% CI: 1.53, 7.23), and mean BMI was significantly higher in non-producers (28.9kg/m²) than in producers (26.7kg/m²), after adjusting for age, ethnicity, and menopausal status. Positive associations with being obese were observed in both peri-menopausal (OR=3.92, 95% CI: 0.90, 17.0) and post-menopausal (OR=3.00, 95% CI: 1.22, 7.70) women. The equol non-producer phenotype was not associated with obesity (OR=1.13, 95% CI: 0.64, 1.98), and mean BMI was not significantly different between equol producers (27.3kg/m²) and non-producers (26.5kg/m²).

CONCLUSIONS

These results suggest that the ODMA non-producer phenotype is associated with obesity in peri- and post-menopausal women. Further work is needed to confirm these observations in additional populations and to evaluate possible mechanisms.

Metabolomics reveals differences between three daidzein metabolizing phenotypes in adults with cardiometabolic risk factors

SCOPE

The soy isoflavone, daidzein, is metabolized by gut microbiota to O-desmethylangolensin (ODMA) and/or equol. Producing equol is postulated as a contributing factor for the beneficial effects of soy.

METHODS AND RESULTS

This randomized, controlled, cross-over design used an untargeted metabolomic approach to assess the metabolic profile of different daidzein metabolizers. Adults (n = 17) with cardiometabolic risk factors received soy nuts or control food for 4 weeks, separated by a 2-week washout. No significant differences were detected pre- and postintervention and between interventions. Examination of the ability to metabolize daidzein revealed three groups: ODMA only producers (n = 4), equol + ODMA producers (n = 8), and nonproducers (n = 5). Analysis of the serum metabolome revealed nonproducers could be distinguished from ODMA-only and equol + ODMA producers. Differences between these phenotypes were related to obesity and metabolic risk (methionine, asparagine, and trimethylamine) with equol + ODMA producers having lower concentrations, yet paradoxically higher pro-inflammatory cytokines. In urine, nonproducers clustered with ODMA producers and were distinct from equol + ODMA producers. Urinary metabolite profiles revealed significantly higher excretion of fumarate and 2-oxoglutarate, as well as pyroglutamate, alanine, and the gut microbial metabolite dimethylamine in equol + ODMA producers.

CONCLUSION

These results emphasize that the serum and urine metabolomes are distinct based on the ability to metabolize isoflavones.

Plasma equol concentration is not associated with breast cancer and fibrocystic breast conditions among women in Shanghai, China

Equol (a bacterial metabolite of the soy isoflavone daidzein) is produced by 30% to 50% of humans and may be associated with health outcomes. We hypothesized that plasma equol would be inversely associated with risks of fibrocystic breast conditions (FBC) and breast cancer (BC). Plasma from women in a breast self-examination trial in Shanghai with BC (n=269) or FBC (n=443), and age-matched controls (n=1027) was analyzed for isoflavones. Equol was grouped into categories (<20, 20-<45, and ≥45nmol/L) and, among women with daidzein ≥20nmol/L, the log10 equol:daidzein ratio was grouped into tertiles. Where available, non-cancerous tissue (NCT) adjacent to the carcinomas from women with BC were classified as non-proliferative or proliferative (n=130 and 172, respectively). The lesions from women with FBC were similarly classified (n=99 and 92, respectively). Odds ratios (OR) and 95% confidence intervals (CI) were calculated across equol categories and tertiles of log10 equol:daidzein ratio. Equol categories were not associated with FBC or BC (P>.05). For log10 equol:daidzein, compared to controls there were positive associations in the mid tertile for proliferative FBC (OR 2.06, 95% CI 1.08-3.93), BC with proliferative NCT (OR 2.95, 95% CI 1.37-6.35), and all BC regardless of histology (OR 2.37, 95% CI 1.43-3.95). However, trends in ORs with increasing plasma equol values or equol:daidzein ratios were not observed (P>.05). The results of this study do not provide evidence that equol plays a role in the etiology of these breast conditions. However, further work is needed to confirm or refute this conclusion.

Equol status and changes in fecal microbiota in menopausal women receiving long-term treatment for menopause symptoms with a soy-isoflavone concentrate

The knowledge regarding the intestinal microbial types involved in isoflavone bioavailability and metabolism is still limited. The present work reports the influence of a treatment with isoflavones for 6 months on the fecal bacterial communities of 16 menopausal women, as determined by culturing and culture-independent microbial techniques. Changes in fecal communities were analyzed with respect to the women's equol-producing phenotype. Compared to baseline, at 1 and 3 months the counts for all microbial populations in the feces of equol-producing women had increased strongly. In contrast, among the non-producers, the counts for all microbial populations at 1 month were similar to those at baseline, and decreased significantly by 3 and 6 months. Following isoflavone intake, major bands in the denaturing gradient gel electrophoresis (DGGE) profiles appeared and disappeared, suggesting important changes in majority populations. In some women, increases were seen in the intensity of specific DGGE bands corresponding to microorganisms known to be involved in the metabolism of dietary phytoestrogens (Lactonifactor longoviformis, Faecalibacterium prausnitzii, Bifidobacterium sp., Ruminococcus sp.). Real-Time quantitative PCR revealed that the Clostridium leptum and C. coccoides populations increased in equol producers, while those of bifidobacteria and enterobacteria decreased, and vice versa in the non-producers. Finally, the Atopobium population increased in both groups, but especially in the non-producers at three months. As the main findings of this study, (i) variations in the microbial communities over the 6-month period of isoflavone supplementation were large; (ii) no changes in the fecal microbial populations that were convincingly treatment-specific were seen; and (iii) the production of equol did not appear to be associated with the presence of, or increase in the population of, any of the majority bacterial types analyzed.

Soy provides modest benefits on endothelial function without affecting inflammatory biomarkers in adults at cardiometabolic risk

SCOPE

Systemic inflammation, endothelial dysfunction, and oxidative stress are involved in the pathogenesis of the metabolic syndrome (MetS). Epidemiological evidence supports an association between whole soy food consumption and reduced risk of cardiovascular disease (CVD). The objective of this randomized, controlled, cross-over study was to evaluate the effects of soy nut consumption on inflammatory biomarkers and endothelial function and to assess whether isoflavone metabolism to secondary products, equol, and/or O-desmethylangolensin (ODMA), modifies these responses.

METHODS AND RESULTS

n = 17 adults at cardiometabolic risk were randomly assigned to the order of two snack interventions, soy nuts, and macronutrient-matched control snack, for four weeks each, separated by a two week washout period. Outcome measures included biomarkers of inflammation, oxidative stress, and glycemic control (ELISA and clinical analyzers), endothelial function, and arterial stiffness (peripheral arterial tonometry (PAT)), and isoflavone metabolites (LC-MS/MS). Results revealed that consuming soy nuts improved arterial stiffness as assessed by the augmentation index using PAT (p = 0.03), despite lack of improvement in inflammatory biomarkers. Addition of equol and/or ODMA production status as covariates did not significantly change these results.

CONCLUSION

Soy nuts when added to a usual diet for one month provide some benefit on arterial stiffness in adults at cardiometabolic risk.

Therapeutic perspectives of epigenetically active nutrients

Many nutrients are known for a wide range of activities in prevention and alleviation of various diseases. Recently, their potential role in regulating human health through effects on epigenetics has become evident, although specific mechanisms are still unclear. Thus, nutriepigenetics/nutriepigenomics has emerged as a new and promising field in current epigenetics research in the past few years. In particular, polyphenols, as part of the central dynamic interaction between the genome and the environment with specificity at physiological concentrations, are well known to affect mechanisms underlying human health. This review summarizes the effects of dietary compounds on epigenetic mechanisms in the regulation of gene expression including expression of enzymes and other molecules responsible for drug absorption, distribution, metabolism and excretion in cancer, metabolic syndrome, neurodegenerative disorders and hormonal dysfunction.

Absorption, distribution, metabolism, and excretion of isoflavonoids after soy intake

Soy is the major source of dietary exposure to isoflavonoids (IFLs). Accumulating evidence supports a role for soy and IFLs in the protection against many chronic diseases including cancer. After soy intake we found a biphasic IFL appearance pattern in plasma as well as in urine that we suggest to be due to IFL absorption in the small intestine (ca. 10%) during the first 2h after intake and IFL absorption in the large intestine (ca. 90%) 4-6 h after intake. While each IFL disappears from the circulation at different times excellent correlations between urinary and circulating IFL values were discovered and algorithms to convert urinary excretion values into circulating levels were established. We suggest the term 'apparent bioavailability' when using urinary data to describe IFL exposure. The IFL bioavailability was found to be influenced by gut bacteria, oral antibiotic treatment (OABX), and an individual's age and health status. While daidzein (DE) and genistein start to be absorbed minutes after intake, equol (EQ) appears in plasma only after a minimum of 8h following soy intake owing to the required transit time of DE to the colon where the conversion of DE to EQ takes place by intestinal microbiota. We have also shown that the apparent IFL bioavailability is higher in children than adults, higher in healthy versus non-healthy individuals, and decreased in children but increased in adults during OABX. Finally, we propose to use a urinary EQ/DE ratio of 0.018 with a DE threshold to identify EQ producers. With this cutoff definition we observed that EQ production is inconsistent over time in 5-30% of both premenopausal and postmenopausal women.

S-(-)equol production is developmentally regulated and related to early diet composition

S-(-)7-hydroxy-3-(4'-hydroxyphenyl)-chroman, or S-(-)equol, a biologically active intestinally derived bacterial metabolite of the soy isoflavones daidzin/daidzein, is not produced in neonatal life. Because its synthesis is dependent on equol-producing bacteria, we hypothesized that early nutrition may influence equol production. This prospective 2.5-year study determined the frequency of S-(-)equol production in healthy infants (n = 90) fed breast milk, soy infant formula, or cow's milk formula in their first year. Urinary S-(-)equol and daidzein were quantified by mass spectrometry after a standardized 3.5-day soy isoflavone challenge. Infants were tested at 6, 9, 12, 18, 24, and 36 months of age, and 3-day diet records were obtained at each visit to explore the effect of early and postweaning (>12 months) macronutrient and micronutrient dietary composition and S-(-)equol production. Use of antibiotics was also recorded. At age 6 months, none of the breast-fed infants produced S-(-)equol, whereas 3.8% and 6.0%, respectively, of soy and cow's milk formula-fed infants were equol producers. By age 3 years, 50% of the formula-fed infants were equol producers, compared with 25% of breast-fed infants. Use of antibiotics was prevalent among infants and may have impacted the stability of S-(-)equol production. No significant differences among the groups were observed in postweaning dietary intakes of total energy, carbohydrate, fiber, protein, fat, saturated fatty acids, or polyunsaturated fatty acids and the propensity to make S-(-)equol. In conclusion, S-(-)equol production is developmentally regulated and initially related to diet composition with the proportion of equol producers increasing over the first 3 years of life, with a trend for formula feeding favoring S-(-)equol production.

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.

Daidzein supplementation decreases serum triglyceride and uric acid concentrations in hypercholesterolemic adults with the effect on triglycerides being greater in those with the GA compared with the GG genotype of ESR-β RsaI

Daidzein (one of the major isoflavones) can be metabolized to equol in certain individuals. The effects of isoflavones alone and equol status on lipid profiles are still controversial. To evaluate the 6-mo effects of daidzein on cardiovascular risk factors in hypercholesterolemic individuals and the interactions of these effects with equol status and estrogen receptor (ESR) genotypes, we conducted a randomized, double-blind, placebo-controlled trial consisting of 210 hypercholesterolemic adults (40-65 y old). The participants were randomly assigned (177 completed) to consume placebo, 40 mg daidzein (DAI40), or 80 mg daidzein (DAI80) daily for 6 mo. Daidzein decreased serum triglycerides (TGs) by 0.15 ± 0.62 mmol/L (mean ± SD) and 0.24 ± 0.61 mmol/L and decreased serum uric acid by 23 ± 47 μmol/L and 29 ± 44 μmol/L in the DAI40 and DAI80 groups, respectively. These reductions in the DAI40 and DAI80 groups were greater than those in the placebo group (P < 0.05). Other blood lipids, glucose, insulin, or glycated hemoglobin did not significantly change after daidzein treatment. No dose-dependent effects of daidzein were found. The reduction of TGs was influenced by the ESR genotype, with a greater effect observed in participants with the GA genotype compared with those with the GG genotype of ESR-β RsaI. These effects were not influenced by equol status. Six-month supplementation of daidzein significantly decreased TGs and uric acid. ESR-β RsaI genotype, not equol status, influenced daidzein's effects on TGs. Daidzein consumption may be effective to improve cardiovascular risk factors, especially in adults with the GA genotype of ESR-β RsaI. This trial was registered at the Chinese clinical trial registry as ChiCTR-TRC-10001048.

Dietary factors influence production of the soy isoflavone metabolite s-(-)equol in healthy adults

S-(-)equol, an intestinally derived metabolite of the soy isoflavone daidzein, is proposed to enhance the efficacy of soy diets. Adults differ in their ability to produce equol when consuming soy foods for reasons that remain unclear. Therefore, we performed a comprehensive dietary analysis of 143 macro- and micronutrients in 159 healthy adults in the United States (n = 89) and Australia (n = 70) to determine whether the intake of specific nutrients favors equol production. Three-d diet records were collected and analyzed using Nutrition Data System for Research software and S-(-)equol was measured in urine by mass spectrometry. Additionally, in a subset of equol producers and nonproducers (n = 10/group), we examined the long-term stability of equol producer status by retesting 12, 18, and 24 mo later. Finally, the effect of oral administration of the antibiotic metronidazole (500 mg/d for 7 d) on equol production was examined in 5 adults monitored during a 4-mo follow-up period. Equol producers accounted for 30.3% and 28.6% of the United States and Australian participants, respectively (overall frequency, 29.6%). No significant differences were observed for total protein, carbohydrate, fat, saturated fat, or fiber intakes between equol producers and nonproducers. However, principal component analysis revealed differences in several nutrients, including higher intakes of polyunsaturated fatty acids (P = 0.039), maltose (P = 0.02), and vitamins A (P = 0.01) and E (P = 0.035) and a lower intake of total cholesterol (P = 0.010) in equol producers. During a 2-y period, equol producer status remained unchanged in all nonproducers and in 80% of equol producers, whereas metronidazole abolished equol production in only 20% of participants. In conclusion, these findings suggest that major differences in the macronutrient content of the diet appear not to influence equol production, but subtle differences in some nutrients may influence the ability to produce equol, which was a relatively stable phenomenon.

Soy proteins and isoflavones reduce interleukin-6 but not serum lipids in older women: a randomized controlled trial

Soy foods contain several components, notably, isoflavones and amino acids, that may improve cardiovascular health. We evaluated the long-term effect of soy protein and/or soy isoflavones supplementation on serum lipids and inflammatory markers using a 1-year randomized, double-blind, placebo-control, clinical trial in 131 healthy ambulatory women older than 60 years. We hypothesized that soy protein, in combination with isoflavones, would have the largest positive effect on coronary heart disease risk factors (serum lipids and inflammatory markers) compared with either intervention alone and that, within groups receiving isoflavones, equol producers would have more positive effects on coronary heart disease risk factors than nonequol producers. After a 1-month baseline period, participants were randomized into 1 of 4 intervention groups: soy protein (18 g/d) and isoflavone tablets (105 mg/d isoflavone aglycone equivalents), soy protein and placebo tablets, control protein and isoflavone tablets, or control protein and placebo tablets. T Tests were used to assess differences between equol and nonequol producers. Ninety-seven women completed the trial. Consumption of protein powder and isoflavone tablets did not differ among groups, and compliance with study powder and tablets was 79% and 90%, respectively. After 1 year, in the entire population, there were either no or little effects on serum lipids and inflammatory markers, regardless of treatment group. Equol producers, when analyzed separately, had significant improvements in total cholesterol/high-density lipoprotein and low-density lipoprotein/high-density lipoprotein ratios (-5.9%, P = .02; -7.2%, P = .04 respectively). Soy protein and isoflavone (either alone or together) did not impact serum lipids or inflammatory markers. Therefore, they should not be considered an effective intervention to prevent cardiovascular disease because of lipid modification in healthy late postmenopausal women lacking the ability to produce equol.

Equol-producing status, isoflavone intake, and breast density in a sample of U.S. Chinese women

BACKGROUND

Differences in ability to metabolize daidzein to equol might help explain inconsistent findings about isoflavones and breast cancer. We examined equol-producing status in relation to breast density, a marker of breast cancer risk, and evaluated whether an association of isoflavone intake with breast density differs by equol-producing status in a sample of Chinese immigrant women.

METHODS

Participants were 224 women, ages 36 to 58 years, enrolled in a study on diet and breast density. All women completed dietary recall interviews, underwent a soy challenge to assess equol-producing status, and received a mammogram assessed for breast density using a computer-assisted method.

RESULTS

In our sample, 30% were classified as equol producers. In adjusted linear regression models, equol producers had significantly lower mean dense tissue area (32.8 vs. 37.7 cm(2), P = 0.03) and lower mean percent breast density (32% vs. 35%, P = 0.03) than nonproducers. Significant inverse associations of isoflavone intake with dense area and percent density were apparent, but only in equol producers (interaction P = 0.05 for both).

CONCLUSIONS

These results support the possibility that equol-producing status affects breast density and that effects of isoflavones on breast density depend on ability to metabolize daidzein to equol.

IMPACT

Although these findings warrant confirmation in a larger sample, they offer a possible explanation for the inconsistent findings about soy intake and breast density and possibly breast cancer risk as well. The findings further suggest the importance of identifying factors that influence equol-producing status and exploring appropriate targeting of interventions.

Vitamin D interactions with soy isoflavones on bone after menopause: a review

Vitamin D is known to increase Ca absorption in adults. However, the threshold vitamin D status to benefit Ca absorption is lower than the target vitamin D status for higher bone mineral density and lower fracture risk, pointing to another pathway for vitamin D to benefit bone. One possibility is by affecting osteoblast and osteoclasts directly. Vitamin D-related bone metabolism may also be affected by soy isoflavones, which selectively bind to the estrogen receptor β and may reduce bone loss in postmenopausal women. We discuss a possible synergistic effect of soy isoflavones and vitamin D on bone by affecting osteoblast and osteoclast formation and activity in postmenopausal women.

Gut metabotypes govern health effects of dietary polyphenols

Polyphenols are thought to be responsible for some of the health effects conferred by a diet rich in fruit and vegetables. Both the formation of bioactive polyphenol-derived metabolites and the modulation of colonic microbiota contribute to these health benefits. Therefore, one cannot infer biological responses from dietary intake records without considering polyphenol-microbiota interactions. However, the latter are complex and subject to large interindividual variability, leading to different polyphenol-metabolizing phenotypes or 'metabotypes'. Based on accurate measurements of intake, exposure and effect on carefully selected samples, the physiological relevance of dietary polyphenols can be evaluated for each metabotype. Ultimately, this will lead to predictive modeling and the development of (personalized) functional foods and other nutraceuticals with maximized health benefits.

Endogenous and exogenous equol are antiestrogenic in reproductive tissues of apolipoprotein e-null mice

Equol is an isoflavone (IF) metabolite produced by intestinal microbiota in a subset of people consuming dietary soy. Equol producers may show different responses to soy foods and phenotypes related to cancer risk. Here, we assessed the effects of soy IF, endogenous microbial equol production, and dietary racemic equol in a 3 × 2 × 2 factorial experiment using gnotobiotic apoE-null mice (n = 9-11/group/sex). At age 3-6 wk, equol-producing microbiota were introduced to one-half of the colony (n = 122). At age 6 wk, mice were randomized to receive a diet that contained 1 of 3 protein sources: casein and lactalbumin, alcohol-washed soy protein (low IF), and intact soy protein (high IF), with total IF amounts of 0, 42, and 566 mg/kg diet, respectively. One-half of each diet group also received racemic equol (291 mg/kg diet). After 16 wk of dietary treatment, serum isoflavonoid profiles varied with sex, soy IF amount, and intestinal microbiota status. There were no treatment effects on tissues of male mice. In females, reproductive tissue phenotypes differed by equol-producing ability (i.e., microbiota status) but not dietary equol or IF content. Equol producers had lower uterine weight, vaginal epithelial thickness, total uterine area, endometrial area, and endometrial luminal epithelial height compared with nonproducers (P < 0.05 for all), with an association between microbiota status and estrous cycle (P > chi-square = 0.03). Exogenous equol reduced expression of progesterone receptor (PGR) and the proliferation marker Ki67 (P < 0.0001) in vaginal epithelium and endometrium; for endogenous equol, only PGR was reduced (P < 0.0005). Our findings indicate that equol diminishes estrogen-dependent tissue responses in apoE-null mice.

Urinary estrogen metabolites in two soy trials with premenopausal women

Background

Soy consumption may protect against breast cancer through modification of estrogen metabolism.

Objective

We examined the effect of soy foods on urinary estrogens and the 2-hydroxy (OH)/16α-OH estrone (E₁) ratio in 2 dietary interventions with premenopausal women.

Methods

BEAN1 was a 2-year randomized trial and BEAN2 a 13-month randomized crossover study. In both interventions, study participants consumed a high-soy diet with 2 soy food servings/day and a low-soy diet with <3 servings of soy/week. Urine samples were collected at baseline and at the end of the diet periods, analyzed for 9 estrogen metabolites by liquid chromatography mass spectrometry, and adjusted for creatinine levels. For BEAN1, 2 samples for 188 participants and for BEAN2, 3 samples for 79 women were analyzed. We applied mixed-effects regression models with log-transformed values of estrogen metabolites and soy intake as the exposure variable.

Results

In BEAN1, no effect of the high-soy diet on individual estrogen metabolites or hydroxylation pathways was observed. The median 2-OH/16α-OH E₁ ratio decreased non-significantly in the intervention group from 6.2 to 5.2 as compared to 6.8 and 7.2 in the control group (p=0.63). In BEAN2, only 4-OHE₁ was significantly lower after the high-soy diet. Interaction terms of the high-soy diet with equol producer status, ethnicity, and weight status revealed no significant effect modification.

Conclusions

Contrary to our hypothesis and some previous reports, the results from 2 well controlled dietary interventions do not support an effect of a high-soy diet on a panel of urinary estrogen metabolites and the 2-OH/16α-OHE₁ ratio.

Equol production changes over time in pre-menopausal women

Equol (EQ) is a metabolite produced by gut bacteria through the chemical reduction of the soya isoflavone daidzein (DE), but only by 30-60% of the population. EQ is believed to provide benefits derived from soya intake and its production is widely viewed as a relatively stable phenomenon. In a randomised, cross-over intervention with soya foods, seventy-nine pre-menopausal women were challenged with a high-soya and a low-soya diet each for 6 months, separated by a 1-month washout period. Overnight urine was collected at three time points during each diet period and analysed for DE and EQ by liquid chromatography tandem MS. Remaining an EQ producer (EP) or non-producer (NP) or changing towards an EP or NP was assessed using an EQ:DE ratio of ≥0·018 combined with a DE threshold of ≥2 nmol/mg creatinine as a cut-off point. We observed 19 and 24% EP during the low-soya and high-soya diet periods, respectively, and found that 6-11% of our subjects changed EQ status 'within' each study period (on an average of 1·2 times), while 16% changed 'between' the two diet periods. The present finding challenges the widely held conviction that EQ production within an individual remains stable over time. The precise factors contributing to changes in EQ status, however, remain elusive and warrant further investigation.

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.

Urinary estrogen metabolites during a randomized soy trial

One of the hypothesized protective mechanisms of soy against breast cancer involves changes in estrogen metabolism to 2-hydroxy (OH) and 16α-OH estrogens. The current analysis examined the effect of soy foods on the 2:16α-OH E(1) ratio among premenopausal women during a randomized, crossover intervention study; women were stratified by equol producer status, a characteristic thought to enhance the protective effects of soy isoflavones. The study consisted of a high-soy diet with 2 soy food servings/day and a low-soy diet with <3 servings of soy/wk for 6 mo each; estrogen metabolites were measured in 3 overnight urines (baseline and at the end of the low- and high-soy diet) using gas chromatography mass spectrometry for the 82 women who completed the study. Urinary isoflavonoids were assessed by liquid chromatography mass spectrometry. When applying mixed models, the 2:16α-OH E(1) ratio increased (P = 0.05) because of a nonsignificant decrease in 16α-OH E(1) (P = 0.21) at the end of the high-soy diet. Similar nonsignificant increases in the 2:16α-OH E(1) ratio were observed in equol producers (P = 0.13) and nonproducers (P = 0.23). These findings suggest a beneficial influence of soy foods on estrogen metabolism regardless of equol producer status.

Estrogen levels in nipple aspirate fluid and serum during a randomized soy trial

BACKGROUND

On the basis of hypothesized protective effect, we examined the effect of soy foods on estrogens in nipple aspirate fluid (NAF) and serum, possible indicators of breast cancer risk.

METHODS

In a crossover design, we randomized 96 women who produced 10 μL or more NAF to a high- or low-soy diet for 6 months. During the high-soy diet, participants consumed 2 soy servings of soy milk, tofu, or soy nuts (∼50 mg of isoflavones per day); during the low-soy diet, they maintained their usual diet. Six NAF samples were obtained using a FirstCyte aspirator. Estradiol (E(2)) and estrone sulfate (E(1)S) were assessed in NAF and estrone (E(1)) in serum only, using highly sensitive radioimmunoassays. Mixed-effects regression models accounting for repeated measures and left-censoring limits were applied.

RESULTS

Mean E(2) and E(1)S were lower during the high-soy than the low-soy diet (113 vs. 313 pg/mL and 46 vs. 68 ng/mL, respectively) without reaching significance (P = 0.07); the interaction between group and diet was not significant. There was no effect of the soy treatment on serum levels of E(2) (P = 0.76), E(1) (P = 0.86), or E(1)S (P = 0.56). Within individuals, NAF and serum levels of E(2) (r(s) = 0.37; P < 0.001) but not of E(1)S (r(s) = 0.004; P = 0.97) were correlated. E(2) and E(1)S in NAF and serum were strongly associated (r(s) = 0.78 and r(s) = 0.48; P < 0.001).

CONCLUSION

Soy foods in amounts consumed by Asians did not significantly modify estrogen levels in NAF and serum.

IMPACT

The trend toward lower estrogen levels in NAF during the high-soy diet counters concerns about adverse effects of soy foods on breast cancer risk.