Equol Production Research Articles

Isoflavone supplement composition and equol producer status affect gene expression in adipose tissue: a double-blind, randomized, placebo-controlled crossover trial in postmenopausal women

Isoflavone supplements, consumed by women experiencing menopausal symptoms, are suggested to have positive effects on menopause-related adiposity and cardiovascular disease risk profile, but discussions about their safety are still ongoing. The objective was to study the effects of an 8-wk consumption of 2 different isoflavone supplements compared with placebo on whole-genome gene expression in the adipose tissue of postmenopausal women. This double-blind, randomized, placebo-controlled crossover intervention consisted of 2 substudies, one with a low-genistein (LG) supplement (56% daidzein + daidzin, 16% genistein + genistin, and 28% glycitein + glycitin) and the other with a high-genistein (HG) supplement (49% daidzein + daidzin, 41% genistein + genistin, and 10% glycitein + glycitin). Both supplements provided ∼ 100 mg isoflavones/d (aglycone equivalents). After the 8-wk isoflavone and placebo period, whole-genome arrays were performed in subcutaneous adipose tissue of postmenopausal women (n = 26 after LG, n = 31 after HG). Participants were randomized by equol-producing phenotype, and data analysis was performed per substudy for equol producers and nonproducers separately. Gene set enrichment analysis showed downregulation of expression of energy metabolism-related genes after LG supplementation (n = 24) in both equol-producing phenotypes and oppositely regulated expression for equol producers (down) and nonproducers (up) after HG supplementation (n = 31). Expression of inflammation-related genes was upregulated in equol producers but downregulated in nonproducers, independent of supplement type. Only 4.4-7.0% of the genes with significantly changed expression were estrogen responsive. Body weight, adipocyte size, and plasma lipid profile were not affected by isoflavone supplementation. Effects of isoflavones on adipose tissue gene expression were influenced by supplement composition and equol-producing phenotype, whereas estrogen-responsive effects were lacking. LG isoflavone supplementation resulted in a caloric restriction-like gene expression profile for both producer phenotypes and pointed toward a potential beneficial effect, whereas both supplements induced anti-inflammatory gene expression in equol producers. The study was registered at clinicaltrials.gov as NCT01556737.

Concerns about Soy Cultivation: What is Known and What is not Known

There is abundant literature suggesting medical use for phytoestrogen-containing products. There is also published evidence suggesting potentially negative consequences of phytoestrogens use for humans. Substantiation of both concepts appears questionable. Meanwhile, soy products are used liberally in the food also for infants and children. The concept discussed here is that it is not consistent to support soy use for estrogenic effects without concern for its impact on routine use as a foodstuff and livestock fodder. It is important for thorough independent studies to be done to answer these questions. Phytoestrogens are substances of plant origin that are structurally and functionally similar to estrogens. Among them, isoflavones and coumestans are the most extensively studied groups. Isoflavones are present in different edible plants, but are most abundant in soy [13]. Consumption of soy products has been associated with favorable health effects, but potentially adverse effects are underacknowledged [4]. Phytoestrogens are advertised as a natural alternative to estrogens for hormone replacement therapy during menopause [1]. Preclinical trials have demonstrated both genomic and non-genomic action of phytoestrogens including selective but weak binding to the estrogen receptors [5]. Some epidemiological studies suggest that dietary intake of phytoestrogens may contribute to the decreased incidence of postmenopausal cardiovascular disease [6] and that phytoestrogens are significantly more effective than placebo in reducing the frequency of hot flashes [7]. Evidence in support of clinically relevant biological effects has been generally rated as insufficient or absent [5,8-14]. A recent review concluded that in spite of increasing preclinical and clinical studies over the past decade, “appealing evidence is still lacking to support the overall positive risk-benefit profile of phytoestrogens” [15]. Then as now, the conventional menopausal hormone replacement therapy remains the only treatment that has consistently had a greater effect than placebo in controlled trials [16]. As evaluation of earlier works on enrichment the diet with soy products has failed to confirm favorable effects related to the cardiovascular system [17], doubts concerning phytoestrogens have recently increased. There is little evidence to support the hypothesis that phytoestrogens protect against menopausal osteoporosis, with published studies having no controls for confounding factors, the observations generally being of short duration [18,19]. In regard to osteoporosis, the latest review concluded that “evidence points to a lack of a protective role of soy isoflavones in the prevention of postmenopausal bone loss” [20], although in vitro and animal studies show some positive effect of isoflavones on bone which has not been clearly confirmed by long-term human trials [21]. There might be genetic differences in this regard, as equol producers seem to present a more positive response to isoflavone intervention [21]. The use of phytoestrogens as an alternative for hormone replacement therapy is not advocated due to insufficient information on safety [22], and reports of adverse effects and interactions with drugs [23]. Moreover, soy is known as allergenic food [2,24], and soybeanbased oil emulsions have been identified as one of the major causes of cholestasis related to pediatric parenteral nutrition [25]. There is a discrepancy in how phytoestrogens and soy products are viewed in science and medicine. Among edible plants, phytoestrogens are most abundant in soy, and are structurally and functionally analogous to estrogens, with their biological action mediated by estrogen receptors. Soy products are widely used in infant food and other foodstuffs; and, at the same time, phytoestrogens have been applied for compensation of hormone deficiency in menopause. Furthermore, soy is applied as livestock fodder, and residual phytoestrogens and their active metabolites can remain in meats. There are only few reports on modified gender-related behavior or feminization in humans as a result of soy consumption. In animals, the intake of phytoestrogens was reported to impact fertility, sexual development and behavior. Feminizing effects in humans can be subtle and identifiable only statistically in large populations, and may be of particular significance for children and adolescents. This matter should be clarified by independent research, which may affect the future of soy cultivation. Citation: Jargin SV (2014) Concerns about Soy Cultivation: What is Known and What is not Known. J Nutr Health Sci 1(3): 310. doi: 10.15744/2393-9060.1.310

Effect of soy nuts and equol status on blood pressure, lipids and inflammation in postmenopausal women stratified by metabolic syndrome status

ObjectiveSoy has been associated with lower risk of cardiovascular disease in Asian countries which consume daily soy. Our study examined whether production of equol, an estrogen metabolite, affected the ability of soy nuts to improve cardiovascular risk factors. Materials/MethodsSixty postmenopausal women participated in a randomized, controlled, crossover trial of a Therapeutic Lifestyle Changes (TLC) diet alone and a TLC diet in which 0.5 cup of soy nuts (25 g of soy protein and 101 mg of aglycone isoflavones) replaced 25 g of nonsoy protein daily. Each diet was followed for 8 weeks at the end of which blood pressure (BP), lipid levels, adhesion molecules and inflammatory markers were measured. ResultsWomen with MetS had significantly higher baseline body mass index (BMI), BP, triglycerides (TG), and soluble intercellular adhesion molecule (sICAM) than women without MetS. In women with MetS on the soy diet, significant reductions in diastolic BP (7.7%; P=0.02), TG (22.9%; P=0.02), C-reactive protein (CRP) (21.4%; P=0.01) and sICAM (7.3%; P=0.03) were noted among equol producers compared to levels on the TLC diet. No significant changes were noted in equol nonproducers. Similarly, in women without MetS, only equol producers had significant reductions in diastolic BP (3.3%, P=0.02) and CRP (30%, P=0.04). In contrast to women with MetS, TG and sICAM levels were not affected in women without MetS, a finding possibly related to lower baseline levels. ConclusionsCardiovascular risk reduction with soy nuts is not uniform and may be greater among producers of equol.

Fecal bacterial community changes associated with isoflavone metabolites in postmenopausal women after soy bar consumption.

Soy isoflavones and their metabolism by intestinal microbiota have gained attention because of potential health benefits, such as the alleviation of estrogen/hormone-related conditions in postmenopausal women, associated with some of these compounds. However, overall changes in gut bacterial community structure and composition in response to addition of soy isoflavones to diets and their association with excreted isoflavone metabolites in postmenopausal women has not been studied. The aim of this study was to determine fecal bacterial community changes in 17 postmenopausal women after a week of diet supplementation with soy bars containing isoflavones, and to determine correlations between microbial community changes and excreted isoflavone metabolites. Using DGGE profiles of PCR amplified 16S rRNA genes (V3 region) to compare microbial communities in fecal samples collected one week before and one week during soy supplementation revealed significant differences (ANOSIM p<0.03) before and after soy supplementation in all subjects. However, between subjects comparisons showed high inter-individual variation that resulted in clustering of profiles by subjects. Urinary excretion of isoflavone (daidzein) metabolites indicated four subjects were equol producers and all subjects produced O-desmethylangolensin (ODMA). Comparison of relative proportions of 16S rRNA genes from 454 pyrosequencing of the last fecal samples of each treatment session revealed significant increases in average proportions of Bifidobacterium after soy consumption, and Bifidobacterium and Eubacterium were significantly greater in equol vs non-S-(-)equol producers. This is the first in vivo study using pyrosequencing to characterize significant differences in fecal community structure and composition in postmenopausal women after a week of soy diet-supplementation, and relate these changes to differences in soy isoflavones and isoflavone metabolites.Trial RegistrationClinicaltrials.gov NCT00244907

Large inter-individual variation in isoflavone plasma concentration limits use of isoflavone intake data for risk assessment.

Background/objectives:Isoflavones are present in soy foods and soy-based supplements. Despite low plasma isoflavone concentrations in the general Western population, concentrations in supplement users exceed those suggested to be beneficial for health in Asian populations, raising concerns for adverse effects. To aid risk assessment, quantification of the relation between isoflavone intake and plasma concentrations is essential.Subjects/methods:Plasma samples were collected from postmenopausal women in three placebo-controlled crossover studies with 8-week periods for supplements (two studies, ~100 mg isoflavones/day, n=88) or 4-week periods for soy foods (one study, ~48 mg isoflavones/day, n=15). Plasma isoflavone concentrations (daidzein, equol, genistein and glycitein) were quantified using high-performance liquid chromatography and electrochemical detection. The association between plasma concentrations and isoflavone intake, equol producer status, intake–producer interaction and background dietary intake was assessed based on the assumption of a log-linear relation.Results:Median plasma total isoflavone concentrations after the soy food and supplement interventions were respectively 2.16 and 3.47 μmol/l for equol producers and 1.30 and 2.39 μmol/l for non-producers. Regression analysis showed that doubling isoflavone intake increased plasma concentrations by 55–62% (±s.e. 1–2%, R2>0.87) for daidzein, genistein, equol (only for producers) and total isoflavones; for glycitein the association was weaker (15±1%, R2=0.48). Adjustments for energy, carbohydrate and fat intake did not affect these estimates. Inter-individual variation, estimated based on repeated measures in one of the studies, was 30–96%.Conclusions:Although the relation between isoflavone intake and plasma concentrations was adequately quantified, the use of isoflavone intake data for risk assessment needs caution due to large inter-individual variation in plasma concentrations.

Randomized controlled trial of whole soy and isoflavone daidzein on menopausal symptoms in equol-producing Chinese postmenopausal women

Dietary supplements containing soy or isoflavones are widely used as alternatives to hormone therapy. However, their efficacy is still inconclusive, and limited data on equol producers are available. The aim of this study was to examine the effect of whole soy (soy flour) or purified daidzein (one major soy isoflavone and the precursor of equol) on menopausal symptoms in equol-producing postmenopausal women, a population most likely to benefit from soy intervention. This is a 6-month parallel-group, double-blind, randomized, placebo-controlled trial. Two hundred seventy equol-producing prehypertensive Chinese postmenopausal women were randomized to one of three treatment groups: 40 g of soy flour (whole soy group), 40 g of low-fat milk powder + 63 mg of daidzein (daidzein group), or 40 g of low-fat milk powder (placebo group) daily, each given as a solid beverage for 6 months. Changes in menopausal symptoms were assessed by a validated and structured symptom checklist at baseline and 6 months. Two hundred fifty-three participants completed the study according to protocol. Urinary isoflavones indicated good compliance with the interventions. Baseline menopausal symptoms were comparable among the three study groups. Intention-to-treat analysis indicated that there was no significant difference in the 6-month changes or percent changes in the total number of menopausal symptoms, in the five dimensions of symptoms, and in the frequencies of individual symptoms among the three treatment groups. Whole soy and purified daidzein have no significant effect on alleviation of menopausal symptoms among equol-producing postmenopausal women with prehypertension.

Effect of whole soy and purified isoflavone daidzein on renal function—a 6-month randomized controlled trial in equol-producing postmenopausal women with prehypertension

ObjectivesThe aim of the study was to examine the long-term effect of commonly used whole soy foods (soy flour) and purified daidzein (one major isoflavone and the precursor of equol) on renal function among prehypertensive postmenopausal women who are also equol producers, a population most likely to benefit from soy intervention. Design and methodsThis was a 6-month double-blind, randomized, placebo-controlled trial. Two hundred seventy eligible Chinese women were randomized to either one of the three treatments: 40g soy flour (whole soy group), 40g low-fat milk powder+63mg daidzein (daidzein group) or 40g low-fat milk powder (placebo group) daily each for 6months. Fasting blood and 24-h urine samples were collected at the beginning and end of trial. Serum creatinine, cystatin C, urea, angiotensin-converting enzyme, minerals and 24-h urinary creatinine and minerals were analyzed. Estimated glomerular filtration rate (eGFR) was calculated with the Cockcroft–Gault and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations. ResultsTwo hundred fifty-three subjects completed the study according to the protocol. Urinary isoflavones indicated good compliance of participants. No significant changes were observed in most of renal parameters, however, there was a less decrease in eGFRcockcroft in 6-month change (p=0.044) and %change (p=0.031) with whole soy intake relative to milk placebo. Subgroup analysis among women with lowered renal function suggested whole soy consumption tended to improve markers of renal function relative to control. ConclusionsSix-month consumption of whole soy tended to have a modest improvement of renal function in prehypertensive postmenopausal women with lowered renal function. Future trials in subjects with more declined renal function are necessary. Trial registrationThe trial was registered in ClinicalTrials.gov with identifier of NCT01270737.(URL: http://clinicaltrials.gov/ct2/show/NCT01270737)

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.

Abstract P073: Urinary Isoflavonoids And Risk Of Ischemic Stroke In Postmenopausal Women

Background: Postmenopausal hormone therapy has been shown to increase stroke risk. It is unclear whether high exposure to pytoestrogens, such as soy isoflavones, may confer the same risk of stroke. Objective: To examine associations of urinary isoflavonoids, which reflect isoflavones intake, absorption, and metabolism, with risk of ischemic stroke in postmenopausal Chinese women. Design: A nested case-control study. Method: We identified 1438 incident cases of ischemic stroke druing 1997-2010 and individually matched them to 1438 controls on age, date and time of sample collection, time since last meal, and recent use of antibiotics. All subjects were postmenopausal women who had never used hormone therapy and had no history of CVD or cancer at baseline. Seven isoflavonoids were measured by LC-MS and standardized by urinary creatinine. Results: We found no significant difference between case-control pairs in mean levels of total or individual urinary isoflavonoids, including 3 parent compounds (daidzein, genistein, and glycitein) and 4 metabolites derived from intestinal bacteria (dihydrogenistein, dihydrodaidzein, O-desmethylangolensin, and equol). Multivariate analyses revealed that women in the highest quintile of equol concentration had a lower risk of ischemic stroke (OR=0.77, 95%CI=0.60-0.98). Analyses stratified by equol producing status showed a significant inverse association between isoflavone bacterial metabolites and stroke risk in equol producers (31.8% of the study population, OR=0.40 across extreme quartiles, 95%CI=0.18-0.87, Ptrend=0.002), but no association in equol non-producers. Conclusion: Overall, this large prospective study suggests that urinary isoflavonoids are not associated with risk of ischemic stroke in postmenopausal Chinese women. High level of bacteria-derived metabolites of isoflavones, however, was associated with a reduced risk in equol producers, suggesting a possible interaction between gut microbiome and soy foods in the pathogenesis of ischemic stroke.

Lactulose Increases Equol Production and Improves Liver Antioxidant Status in Barrows Treated with Daidzein

Equol, one of the intestinal microflora metabolites of daidzein, has gained much attention for having greater bioactivity than its precursor (daidzein and daidzin) and seeming to be promoted by hydrogen gas. The effects of lactulose on the equol-producing capacity and liver antioxidant status of barrows treated with daidzein were investigated in this study. Male castrated piglets (barrows) of Landrace×Duroc, aged 40 days, were randomly divided into the following three groups: control group (C, n = 12, fed an isoflavones-free basic diet), daidzein group (D, n = 12, fed an isoflavones-free basic diet with 50 mg/kg of daidzein supplementation) and daidzein+lactulose group (D+L, n = 12, fed an isoflavones-free basic diet with 1% of lactulose and 50 mg/kg of daidzein supplementation). After 20 days, the profile of short-chain fatty acids in the colon digesta showed that lactulose significantly increased the fermented capacity in the gastrointestinal tract of the barrows. First-void urinary equol concentrations were significantly higher in the D+L group than in the D group (3.13±0.93 compared to 2.11±0.82 μg/ml, respectively). Furthermore, fecal equol levels were also significantly higher in the D+L group than in the D group (12.00±2.68 compared to 10.00±2.26 μg/g, respectively). The population of bacteroidetes and the percentage of bacteroidetes to bacteria in feces were higher in the D+L group than in the D group. The DGGE profiles results indicate that lactulose might shift the pathways of hydrogen utilization, and changing the profiles of SRB in feces. Moreover, the D+L group had weak enhancement of T-SOD and CuZn-SOD activities in the livers of barrows treated with daidzein.

Obesity prevalence in relation to gut microbial environments capable of producing equol or O-desmethylangolensin from the isoflavone daidzein

Studies have observed associations between the gut microbiome and obesity. O-desmethylangolensin (ODMA) and equol are gut bacterial metabolites of daidzein, a compound found in high amounts in soy foods. Approximately 80-95% and 25-60% of individuals harbor gut microbial communities capable of producing ODMA or equol, respectively. Given that other phenotypes of gut bacterial metabolism of dietary compounds have been associated with obesity, we hypothesized that daidzein-metabolizing phenotypes would be associated with obesity. The objective of this study was to compare the prevalence of ODMA-producer and equol-producer phenotypes in obese, overweight and normal-weight individuals. Adults aged 18-95 years (n=297) provided a first-void urine sample after a 3-day soy challenge, and urinary ODMA and equol concentrations were used to classify individuals as producers or non-producers. Body mass index was calculated from self-reported weight and height. There were 60 ODMA non-producers and 173 equol non-producers. Obese individuals were 2.8 times more likely to be ODMA non-producers (odds ratio (OR)=2.8, 95% confidence interval (CI): 1.2, 6.2) compared with normal-weight individuals, when adjusted for age, race (white vs non-white), and gender and menopausal status (male, premenopausal female and postmenopausal female). Obesity was not associated with equol-producer phenotype (OR=1.1, 95% CI: 0.5, 2.2). Stronger associations with obesity were observed in the ODMA non-producers who were also equol producers than in the equol non-producers. Results from this analysis suggest that the ODMA-producer phenotype, but not equol-producer phenotype, is associated with obesity in adults. These results support further work to replicate these findings and evaluate the mechanisms of the observed associations.

Cardiovascular Risks in Relation to Daidzein Metabolizing Phenotypes among Chinese Postmenopausal Women

BackgroundStudies suggested that the inter-individual differences in metabolizing isoflavone daidzein to equol or O-desmethylangolensin (ODMA) might explain the inconsistency of the soy/isoflavones efficacy on cardiovascular health.ObjectivesThe study aims to evaluate the relationship between equol and ODMA phenotypes and cardiovascular risks with habitual isoflavone consumption in Chinese postmenopausal women.MethodsThis is a cross-sectional study among 726 prehypertensive postmenopal women who were screened for a randomized controlled trial. 648 women returned a daidzein-challenged urine samples for determination of equol and O-DMA production. 595 attended clinic visits for assessment of cardiovascular risks including body composition, blood pressure (BP), serum lipids, uric acid, high sensitivity C-reactive protein (hs-CRP), fasting glucose and free fatty acid (FFA).ResultsThe prevalences of equol and O-DMA producers were 53.2% and 60.9% respectively. Equol producers had higher fat free mass (p = 0.001), lower systolic (p = 0.01) and diastolic (p = 0.01) BP, serum triglyceride (p = 0.023), hs-CRP (p = 0.015) and FFA (p = 0.001) than non-producers. O-DMA producers had lower body fat% (p = 0.032), SBP (p = 0.02), total cholesterol (p = 0.002) than non-producers. The significant differences remained after further adjustment for potential confounders. The habitual soy isoflavones intake had little relation to cardiovascular risk factors in either equol/O-DMA producer phenotypes.ConclusionEquol/O-DMA producers had more favorable cardiovascular risk profiles than non-producers in prehypertensive postmenopausal women.

Equol producers can have low leptin levels among prediabetic and diabetic females

ObjectivesSoy isoflavones have received great attention for their beneficial effects on health and disease, i.e., in patients with diabetes. Equol is a biologically active isoflavone-related metabolite with interindividual differences in its production. The current study investigated the relationship between an equol-producing state and the levels of adipocytokine markers in a prediabetic and diabetic population. Subjects and methodsA total of 79 subjects (34 males/45 females) in a prediabetic or diabetic state recruited from the general population were examined regarding their ability to produce equol using urine samples. Clinical data, such as age, smoking as well as anthropometric and biochemical variables, including body mass index (BMI), lipids, insulin, glucose, hemoglobin A1c, leptin and adiponectin, were recorded. ResultsEquol producers exhibited lower leptin and leptin/BMI than non-producers among females. Simple correlation tests and stepwise multiple regression analyses revealed a significant inverse correlation between the leptin/BMI and equol-production. This relationship was not found in males. ConclusionsFemale equol producers can have favorable metabolic traits in relation to leptin metabolism in this population. Further studies are needed to confirm these results.

Isoflavones in Japanese and Caucasian men with prostate cancer in Hawaii.

241 Background: Recently, several studies have reported that soy isoflavones and the ability to produce Equol, an active derivative of soy isoflavone, may play a role in the suppression of prostate cancer. An Equol-producing bacterium, Slackia sp. strain NATTS has been identified in stool cultures. To further investigate this relationship, we evaluated Japanese-Americans (JA) and whites (W) in Hawaii, with and without prostate cancer, with regards to dietary soy intake, serum isoflavone levels, and the presence of stool NATTS. Methods: The serum levels of Daidzein, Genistein, Glysitein, Dihydrodaidzein (DHD), Equol, o-desmethylangolensin (o-DMA) and total isoflavone was determined in 65 JA (34 patients with prostate cancer , 31 controls) and 68 W (34 patients with prostate cancer , 34 controls) subjects. The control group consisted of age matched cancer-free male subjects. To evaluate Equol producing ability, we assessed the presence of NATTS in stool samples. All subjects completed a lifetime dietary soy consumption survey. Results: The serum level of Genistein and o-DMA were significantly higher in JA (Genistein: W 21.5±54.0, JA 61.8±150.9, p=0.04; o-DMA: W 0, JA 2.0±7.9, p=0.04). Daizein level trended higher in JA (W 13.9±34.7, JA 33.3±84.0, p=0.09). Glysitein level was significantly higher in W (W 35.7±10.4, JA 30.7±15.5, p=0.03). No differences were noted in DHD and Equol levels between W and JA. Total isoflavone level trended higher in JA (W 76.3±104.9, JA 135.1±245.6, p=0.07). There were no differences in serum isoflavone level between prostate cancer patients and controls for both JA and W. Only 10 of 120 stool samples were positive for NATTS (8.6%), a rate much lower than seen in Japan. JA showed higher intake of soy than W. Conclusions: The high soy consumption and isoflavone levels in JA may be related to the observed lower incidence of prostate cancer relative to W in Hawaii. The near absence of equal producers in Hawaii JA may contribute to their higher incidence of prostate cancer compared to Japan based Japanese. These results suggest that both soy isoflavone levels and Equol production may be inversely associated with prostate cancer incidence.

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.

Lactulose promotes equol production and changes the microbial community during in vitro fermentation of daidzein by fecal inocula of sows

Equol has higher biological effects than other isoflavones. However, only about 30–50% of humans possess a microbiota capable of producing equol from dietary daidzein. In recent years, interest has grown in dietary applications to improve equol production in human and other animals. In this study, lactulose was used as a potential equol-promoting prebiotic in vitro. The effect of lactulose on transformation of daidzein into equol by sows' fecal microbiota was investigated. Results showed that lactulose treatment improved bacteria growth parameters, changing the kinetics of fermentation in vitro. Lactulose significantly increased total gas production, T1/2, Tmax, and Rmax. Furthermore, lactulose altered the microflora composition, increased equol production associated with a reduction in the population of methanogen and increased the sulfate-reducing bacteria population during 24 h of incubation. Here, we report for the first time that in a certain condition (sealing or high pressure), via a dihydrodaidzein (DHD) pathway equol might be able to reform to daidzein by further metabolism using lactulose as a substrate. This study proposes that “hydrogen-producing prebiotic” might be a novel way to promote equol production in vivo or in vitro.

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.

Whole soy, but not purified daidzein, had a favorable effect on improvement of cardiovascular risks: A 6‐month randomized, double‐blind, and placebo‐controlled trial in equol‐producing postmenopausal women

Equol is produced by the intestinal bacteria from isoflavone daidzein. Studies have reported the health benefits of soy can only present or more pronounced in equol producers. This 6-month randomized controlled trial examined the effect of whole soy (soy flour) and purified daidzein on cardiovascular biomarkers and carotid intima-media thickness (CIMT) in prehypertensive postmenopausal women who were equol producers. Two hundred seventy eligible women were randomized to either one of the three treatments: 40 g soy flour (whole soy group), 40 g low-fat milk powder + 63mg daidzein (daidzein group), or 40 g low-fat milk powder (placebo group) daily each for 6 months. Fasting venous samples were obtained at baseline and end of trial for testing glucose, lipids, high sensitivity C-reactive protein (hs-CRP), and free fatty acid. Changes in common CIMT were also assessed. Serum LDL-C decreased by 7.95% (95% CI: -15.09∼-0.81%) and 6.32% (95% CI: -13.45∼0.08%), and serum hs-CRP decreased by 0.164 (95% CI: -0.309∼-0.019) and 0.054 (95% CI: -0.199∼0.012) in the whole soy group compared with daidzein and milk placebo groups, respectively. No significant change in CIMT was found. Whole soy, but not purified daidzein, had a beneficial effect on reduction of LDL-C and hs-CRP among prehypertensive equol-producing postmenopausal women.

Effects of daidzein and kiwifruit on bone mineral density and equol production in ovariectomised rats

In this study, we investigated the synergistic effects of daidzein (Dz) and kiwifruit on bone and equol production in ovariectomised (OVX) rats. Female Sprague-Dawley rats were randomly assigned to one of five groups: sham operated, OVX control, OVX fed 0.1% Dz-supplemented diet (OVX + Dz), OVX fed 0.1% Dz and green kiwifruit (GRK)-supplemented diet (OVX + Dz + GRK) and OVX fed 0.1% Dz and gold kiwifruit (GOK)-supplemented diet (OVX + Dz + GOK). There were no significant differences in whole body and femur bone mineral density (BMD) among groups at week 8. BMD in the OVX group significantly decreased at week 8; however, BMD in the OVX + Dz + GRK was not significantly different from baseline in the end of the study. However, supplementation with kiwifruit did not affect urinary equol concentrations, urinary ratios of equol to Dz and the composition of caecal microbiota. These results suggest that the combination of Dz and GRK may slightly reduce bone loss caused by oestrogen deficiency but does not affect equol production.

Equol-Producing Status, Isoflavone Intake, and Breast Density in a Sample of U.S. Chinese Women

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. 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. 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). 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. 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.