Consumption Of Phytoestrogens Research Articles

From phytoestrogens to obesity and the metabolic syndrome: Health from food and food for health.

ISSN 1555-8932 print, Copyright © 2006 by New Century Health Publishers, LLCwww.newcenturyhealthpublishers.comAll rights of reproduction in any form reservedPhytoestrogens are defined as naturally occurring molecules ofplant origin, capable of acting as estrogen hormone mimetics orantagonists, but also as endocrine disruptors (Committee onToxicity of Chemicals in Food 2003). Public research andindustry have posed increasing interest in these plant-derivedsubstances in the last decade. Many of them have been marketedas dietary supplements or nutraceuticals with health claims, leadingto significant increase in phytoestrogen consumption levels in theWestern population (Davis et al. 1999). Even though severalreports are available suggesting health-promoting effects for thesecompounds in preventing age-related diseases such asatherosclerosis, hormone-dependent cancers, and osteoporosis(Davis et al. 1999; Adlercreutz 2002), the mechanistic aspects oftheir activity have not been fully clarified and a wide consensus ofthe pros and cons of their use in humans has not been reached bythe scientific community. It is clear however that, similarly tonatural estrogens, these dietary compounds act on cellularresponses through binding to the estrogen receptors (ERs): theirbeneficial or adverse effect is unpredictable, because it dependson their capacity to act as agonist or antagonist in each cell type,on the tissue and cell-specific expression of ER-coregulators, andalso on the endogenous estrogen levels. Such interactions havebeen reported for both the “genomic” mode of action of ERs,based on binding of the activated receptors with the EstrogenResponsive Elements (EREs), or interacting with othertranscription factors, such as AP-1 and SP-1, as well as for the fast“non genomic” effects that proceed through kinase-mediated signaltransduction pathways such as ERK/MAPK, PI3K/AKT andPKC (Harris et al. 2005; Waring & Harris 2005).Besides isoflavones, the most common and studied polyphenols,other molecules have been reported to interact with steroidreceptors, among which flavonoids, tannins, stilbenes, lignans,tocotrienols. It might appear somehow surprising that so manydifferent molecules share the ability to regulate a signalingpathway, especially considering that specificity, which is the abilityto discriminate between different ligands, is the most importantand typical feature of cellular signaling mediated by nuclearreceptors (Vasudevan et al. 2002; Smith & O’Malley 2004).

Effects of Neonatal Resveratrol Exposure on Adult Male and Female Reproductive Physiology and Behavior

Resveratrol (RES) is a phytoestrogen that has the ability to bind to estrogen receptors (ERs) and evoke biological effects that parallel those exerted by endogenous and synthetic estrogens. We have shown in previous studies that adult female rats acutely exposed to RES exhibit estrous cycle irregularity, ovarian hypertrophy, and alterations in sociosexual behavior. The present experiment characterizes the prolonged effects of maternal RES exposure throughout the lactational period on subsequent behavior, reproductive tissues, and brain morphology of the adult offspring. During adulthood, female offspring exposed to RES throughout nursing exhibited reduced body weight and increased ovarian weight, but exhibited normal estrous cyclicity and sociosexual behavior, without changes in the volume of the sexually dimorphic nucleus of the preoptic area or the anteroventral periventricular nucleus of the hypothalamus. During adulthood, males exposed to RES throughout nursing exhibited decreased body weight and plasma testosterone concentration, increased testicular weight, and reduced sociosexual behavior. These males also had significantly smaller sexually dimorphic nucleus of the preoptic area volumes and larger anteroventral periventricular nucleus volumes compared to male controls. These data suggest that postnatal exposure to RES may affect estrogenic activity in specific peripheral tissues (e.g., the gonads), while inducing antiestrogenic effects in the brain. Thus, the present study supports recent in vitro and in vivo findings that RES differs from most other phytoestrogens by acting as a possible mixed ER agonist/antagonist, depending on the tissue-specific availability of ER subtypes that are preferentially localized in specific brain regions and throughout the reproductive tract. More importantly these data indicate that maternal consumption of phytoestrogens during lactation can have lasting effects on the offspring that may not become apparent until they reach adulthood.

Reliability and Validity of an Assessment of Usual Phytoestrogen Consumption (United States)

To evaluate the reliability and validity of a food-frequency questionnaire (FFQ) and database designed to quantify phytoestrogen consumption. This study included 195 members of the California Teachers Study (CTS) cohort who, over a 10-month period, completed four 24-h dietary recalls, a pre- and post-study FFQ, and provided two 24-h urine specimens. Participants (n = 106) in a parallel study (and 18 women who dropped out of the long-term study) completed a single recall and FFQ, and provided one 24-h urine specimen. Urinary phytoestrogens were determined using liquid chromatography-mass spectrometry. Reliability and validity were evaluated using Shrout-Fleiss intraclass correlations and energy-adjusted deattenuated Pearson correlations, respectively. Correlations reflecting the reproducibility of the FFQ phytoestrogen assessment ranged from 0.67 to 0.81. Validity correlations (FFQ compared to dietary recalls) ranged from 0.67 to 0.79 for the major phytoestrogenic compounds (i.e., daidzein, genistein, and secoisolariciresinol) and 0.43 to 0.54 for the less common compounds. Compared to urinary levels, validity correlations ranged from 0.41 to 0.55 for the isoflavones and 0.16 to 0.21 for total lignans. Our isoflavone assessment is reproducible, valid, and an excellent tool for evaluating the relationship with disease risk in non-Asian populations. Further research is needed before these tools can accurately be used to assess lignan consumption.

Variation in commercial rodent diets induces disparate molecular and physiological changes in the mouse uterus

Although ovarian estrogen, estradiol-17beta, is a key modulator of normal reproductive functions, natural and synthetic compounds with estrogen-like activities can further influence reproductive functions. Plant-derived phytoestrogens specifically have received much attention because of associated health benefits. However, a comprehensive understanding of the beneficial and/or detrimental impacts of phytoestrogen consumption through commercial rodent diets on uterine biology and early pregnancy at the molecular level remains largely unexplored. Using multiple approaches, we demonstrate here that exposure of adult female mice to a commercial rodent diet with higher phytoestrogen levels facilitates uterine growth in the presence or absence of ovarian estrogen, alters uterine expression of estrogen-responsive genes, and advances the timing of implantation compared with a diet with lower phytoestrogen levels. The finding that variability in phytoestrogen content in commercial rodent diets, both within and between brands, influences experimental results stresses the importance of this investigation and raises caution for investigators using rodents as animal models.

The Importance of Phytoestrogens in Food Supplements and Phytopharmaceuticals

Different natural products from the plant kingdom including isoflavones, prenylflavones, coumestans, stilbenes, and lignans can cause endocrine perturbations, especially on the estrogenic hormonal pathway because of their structural analogies to estradiol. Several studies report the presence of such compounds in food, the richest source being soy and soy products. These substances, commonly called phytoestrogens, are known to influence the human hormonal profile and soy preparations are being considered for use as post-menopausal estrogen replacement therapy. Numerous clinical and epidemiological reports have studied the influence of phytoestrogens on the development of hormone-dependent cancers. The effect on genital development of postnatal phytoestrogen exposure is still under debate. Consumption of phytoestrogens may also influence the incidence of bone diseases, atherosclerosis, or Alzheimer's disease. This article summarizes the classification of phytoestrogens, their pharmacological evaluation and properties, and the methods used for their identification.

Urinary phytoestrogen concentrations in the U.S. population (1999–2000)

We report population-based urinary concentrations of phytoestrogens stratified by age, sex, and composite racial/ethnic variables. We measured the isoflavones - genistein, daidzein, equol, and O-desmethylangolensin (O-DMA) - and the lignans - enterolactone and enterodiol - in approximately 2500 urine samples from individuals aged 6 years and older who participated in the National Health and Nutrition Examination Survey (NHANES) in 1999 and 2000. We detected all phytoestrogens in over 70% of the samples analyzed; enterolactone was detected in the highest concentrations, and daidzein was detected with the highest frequency. The geometric means for each phytoestrogen were as follows: genistein, 22.3 microg/g; daidzein, 68.6 microg/g; equol, 7.65 microg/g; O-DMA, 3.95 microg/g; enterolactone, 217 microg/g; and enterodiol, 24.3 microg/g creatinine. The 95th percentiles for each phytoestrogen were as follows: genistein, 380 microg/g; daidzein, 944 microg/g; equol, 50.3 microg/g; O-DMA, 217 microg/g; enterolactone, 2240 microg/g; and enterodiol, 240 microg/g creatinine. Multivariate analyses showed statistically significant differences among many of the demographic subgroups. Adolescents had higher concentrations of genistein and equol than adults. Non-Hispanic whites had higher concentrations of enterodiol and equol than Mexican Americans or non-Hispanic blacks. Non-Hispanic whites also had higher concentrations of enterolactone and O-DMA than Mexican Americans. Mexican Americans had higher concentrations of genistein than non-Hispanic blacks; however, the opposite was found for O-DMA. Determination of phytoestrogen exposure in the US population will help us to better understand phytoestrogen consumption in the US and will assist us in elucidating the potential role of phytoestrogens in protecting against cancer and heart disease.

Phytoestrogen exposure elevates PTEN levels

Epidemiological data suggest that consumption of phytoestrogens can be protective against the development of breast cancer. It may be logical to postulate that phytoestrogens may regulate proteins that control cellular division, such as the tumor suppressor PTEN. Germline, and more significantly, somatic PTEN mutations have been observed in a broad range of human cancers, especially those of the breast. Active PTEN results in decreased phosphorylation of Akt and MAPK, the up-regulation of p27 and down-regulation of cyclin D1 protein levels resulting in decreased proliferation and an increase in apoptosis. We hypothesized that phytoestrogen exposure regulates PTEN protein expression in the breast cancer cell line, MCF-7. When MCF-7 cells were stimulated with resveratrol, quercetin or genistein, there was an increase in PTEN protein levels. Concomitantly, phytoestrogen stimulation resulted in decreased Akt phosphorylation and an increase in p27 protein levels, indicating active PTEN lipid phosphatase activity. In contrast, we found that MAPK phosphorylation and cyclin D1 levels, which are regulated by PTEN's protein phosphatase activity, were not altered. Using semi-quantitative RT-PCR, we found that mRNA levels were slightly increased in cells stimulated by phytoestrogens, suggesting that the mechanism for increased PTEN protein expression is dependent upon transcription. Concurrently, our data provide evidence that a mechanism for phytoestrogens' protective nature is partially through increased PTEN expression. More importantly, it provides a novel target for the regulation of PTEN expression and suggests that dietary changes may be adjunctive to traditional preventive and therapeutic strategies against breast cancer.

A rye bran diet, rich in plant lignans, has no influence on the composition of the gut microflora in postmenopausal women

The consumption of phytoestrogens has been related to a reduced risk of hormone-dependent cancer types as well as coronary heart diseases. Plant lignans that represent one class of phytoestrogens are found in relatively high concentrations in rye bran. When consumed, they are metabolized into mammalian lignans (enterodiol and enterolactone) by gut bacteria. In order to investigate whether an increased intake of plant lignans had an impact on the composition of the predominant bacterial community of the human gut a 2x6-week intervention study, with a crossover design, was conducted. Eighteen healthy postmenopausal women (age 55-71 years) were recruited and randomly assigned to two groups. The intervention comprised bread products with either rye bran or an inert wheat cellulose (Vitacel† ). Faecal samples were collected before and at the end of each intervention period and analysed for their predominant bacterial species composition by a cultivationindependent approach - polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). The rye bran diet had no impact on the composition of gut microflora. However, the DGGE profiles demonstrated unique bacterial communities for each individual, which implied a differing efficiency among individuals to metabolize lignans. Key words: rye bran, lignans, human gut microflora, PCR-DGGE

Effects of dietary phytoestrogens on core body temperature during the estrous cycle and pregnancy

Phytoestrogens have received increased investigative attention due to their potential protective effects in connection to age-related diseases and hormone-dependent cancers. Phytoestrogens appear to be an effective treatment during perimenopause where symptoms, such as hot flashes are reduced. However, little is known about the influence of phytoestrogens on core body temperature during various hormonal conditions. This study examined the effects of dietary phytoestrogens on core body temperature during estrous cycles or pregnancy by feeding Long–Evans rats either a diet rich in phytoestrogens (Phyto-600) versus a diet relatively low in phytoestrogens (Phyto-free). Independent of treatments, body temperature was highest at proestrus and declined during estrus and diestrus. Moreover, the consumption of the Phyto-600 diet moderately decreased body temperature during proestrus, estrus and diestrus versus Phyto-free-fed animals. During pregnancy, independent of treatments, core body temperature decreased as a function of increasing gestational length. Phyto-600-fed rats displayed significantly decreased body temperatures (by approximately 0.5 °C) from gestation days 6 to 19, compared to Phyto-free values. The results from this study indicate that consumption of dietary phytoestrogens alters the neuroendocrine mechanism of core body temperature regulation that may help explain, in part, the beneficial effects of phytoestrogens for hot flashes.

Phytoestrogens: Implications in Neurovascular Research

The early discontinuation of the Women's Health Initiative trial evaluating the effects of estrogen plus progestin due to concerns about the risk-benefit ratio of this steroid combination therapy emphasizes the need to examine alternative methods of estrogen replacement. One such alternative is isoflavone consumption of soy-derived dietary phytoestrogens that have received prevalent usage due to their ability to decrease age related disease (cardiovascular and osteoporosis), hormone-dependent cancers (breast and prostate), and peri- and postmenopausal symptoms. Differences in dietary phytoestrogen consumption result in large variations in somatic phytoestrogen content. These molecules affect estrogen and estrogen receptor function in several ways, including having both agonist and antagonist effects on estrogen receptors, as well as functioning like natural selective estrogen receptor modulators. Similar to estrogens, dietary phytoestrogens appear to affect certain aspects of vascular, neuroendocrine, and cognitive function. This article reviews health effects of estrogen, isoflavones and their hormonal mechanism of action, brain penetration by isoflavones, heath effects of isoflavones, and effects of isoflavones on vascular, neuroendocrine, and cognitive function. Because of their diverse health effects and widespread availability in soy foods, dietary phytoestrogens merit continued research into their effects on human health and cognitive function.

Soy Protein: No Cognitive, BMD, or Lipid Benefit

With the Women's Health Initiative studies demonstrating that the overall risks associated with hormone therapy outweigh its preventive effect on cancer and heart disease, clinicians and patients are seeking alternative ways to mitigate the effects of aging and to control menopausal symptoms. Population-based and animal studies have suggested that consumption of phytoestrogens, found in soy, nuts, and grains, might be …

Effects of genistein or soy milk during late gestation and lactation on adult uterine organization in the rat.

In utero and lactational exposure to estrogenic agents has been shown to influence morphological and functional development of reproductive tissues. Thus, consumption of dietary phytoestrogens, such as isoflavones, during pregnancy and lactation could influence important periods of development, when the fetus and neonate are more sensitive to estrogen exposure. In this study, reproductive outcomes after developmental exposure to isoflavones were examined in Long-Evans rats maternally exposed to isoflavones via a commercial soy beverage or as the isolated isoflavone, genistein. Most reproductive endpoints examined at birth, weaning, and 2 months of age were not significantly modified in pups of either sex after lactational exposure to soy milk (provided to the dams in place of drinking water) from birth until weaning. However, soy milk exposure induced a significant increase in progesterone receptor (PR) in the uterine glandular epithelium of the 2-month-old pups. In pregnant dams treated with genistein (GEN; 15 mg/kg body weight) by gavage, from Gestational Day 14 through weaning, PR expression in the uterine glandular epithelium from 2-month-old GEN-treated females (postexposure) was also significantly increased. Diethylstilbesterol (DES) also stimulated uterine PR expression only in the glandular but not luminal epithelial cells. However, unlike DES, in utero/lactational exposure to GEN did not increase expression of the proliferation marker, proliferating cell nuclear antigen (PCNA), in the luminal epithelial cells of the 2-month-old rat uteri. These experiments demonstrate that developmental exposure to dietary isoflavones, at levels comparable to the ranges of human exposure, modify expression of the estrogen-regulated PR in the uterus of sexually mature rats weeks after exposure ended. Since the PR is essential for regulating key female reproductive processes, such as uterine proliferation, implantation, and maintenance of pregnancy, its increased expression suggests that soy phytoestrogen exposure during reproductive development may have long-term reproductive health consequences.

Soy and bone. Where do we stand?

Interest in the use of plant estrogens (phytoestrogens) to attenuate postmenopausal bone loss has increased during the past 10 years as healthcare consumers, practitioners, and scientists have searched for alternative treatments to the use of hormone replacement therapy. Promising research has emerged regarding the potential benefit of increased consumption of phytoestrogens, primarily from dietary soy products. Dietary phytoestrogens, primarily isoflavones found in soy foods, may alter bone turnover in postmenopausal women by decreasing bone resorption and increasing bone formation.

Phytoestrogen Intake and Endometrial Cancer Risk

Certain plant foods such as soybeans, whole grains, seeds, and dried fruit contain phytoestrogens that have anti-estrogenic properties that lower endogenous estrogen levels and can offer women some protection against the development of endometrial cancer. This study investigated the association of 3 forms of phytoestrogens (isofavones, coumestrol, and lignans) with the risk of endometrial cancer. Study subjects were 500 women with a diagnosis of endometrial cancer who were identified in and recruited from the Greater Bay Area Cancer Registry and the California Cancer Registry. They were black, Latina, and white women 35 to 79 years of age. A control group, matched for age and ethnicity to participants, consisted of 470 women found through random-digit dialing. Subjects in both groups were interviewed about dietary habits using a food-frequency questionnaire adapted from Block's Health History and Habits Questionnaire. On average, study subjects and control subjects had similar consumption of phytoestrogens, including all isoflavones, coumestrol, and the lignan matairesinol, but primary lignan secoisolariciresinol consumption was higher in study subjects than control subjects (P = .05). When compared by quartiles, women in the highest quartile of intake of isoflavones and lignans had a lower risk of endometrial cancer compared with those in the lowest quartile (odds ratio, 0.68 vs. 5.9, respectively). A comparison of different compounds adjusting for age, ethnicity, and total caloric intake found that consumption of the major isoflavones genistein and daidzein and the lignan seciosolariciresinol was associated with lower risk of endometrial cancer (P = .08, 0.02, and 0.001, respectively). Postmenopausal status strengthened these associations (P ≤.05 for isoflavones and 0.05≤ P ≥.08 for lignans). Obese women (body mass index greater than 32.23 m 2 ) who consumed the lowest levels of isoflavones or lignans had the greatest risk of endometrial cancer (odds ratio 6.9 for isoflavones and 4.7 for lignans).

Determination of rat oral bioavailability of soy-derived phytoestrogens using an automated on-column extraction procedure and electrospray tandem mass spectrometry

In recent years, consumption of herbal supplements as an alternative to pharmaceutical drug therapy has increased. For example, with the health claims labeling which describes the link between soy-protein and a reduced risk of coronary heart disease (CHD), the consumption of soy and soy-derived phytoestrogens has increased dramatically. That being said, the oral bioavailability of only a few soy phytoestrogens such as Daidzein and Genestein have been previously estimated. In this paper, we present the calculated percent of rat oral bioavailability of five soy-derived phytoestrogens (Genistein, Daidzein, Biochanin A, Coumestrol, and Zearalenone) in male Sprague–Dawley rats. The plasma quantitation required for the bioavailability calculation is performed by using a rapid on-line plasma extraction procedure for the quantitative analysis. To further speed up the analysis the rats were dosed using the ‘n-in-one’ (cassette) protocol. The rapid on-line extraction/quantitation methodology coupled to the cassette dosing analysis of phytoestrogens is the key point of this paper. The limit of quantitation (LOQ) for each compound was 1–1000 ng/ml with each plasma sample analysis taking less than 2 min. In general the percent oral bioavailability was determined to be between 11 and 28%.

Soy infant formula and phytoestrogens.

Soy infant formula contains high levels of the isoflavones, genistein and daidzein, which are commonly referred to as phytoestrogens. These are non-steroidal chemicals with structural similarities to estrogen. Infants consuming soy formula have high levels of circulating isoflavones. These are an order of magnitude greater than the levels of isoflavones which have been shown to produce physiological effects in adult women consuming a high soy diet. There is conflicting evidence about the risks and benefits of soy phytoestrogens, with research presenting a contradictory picture. Some reviewers suggest that early exposure to soy may prevent cancer and heart disease. However, there is very little research on the effects of consumption of soy phytoestrogens by human neonates. Against this generally positive view there is an increasing number of recent reports that suggest that in experimental animals, phytoestrogens have adverse effects with respect to carcinogenesis, reproductive function, immune function, and thyroid disease. Despite the absence of adequate scientific research that quantifies the level of risk to infants, most would argue for a precautionary approach to be taken in situations where there are potential developmental effects from the consumption of pharmacologically active compounds in infancy and childhood.

Estrogens and phytoestrogens: brain plasticity of sexually dimorphic brain volumes

Sexually dimorphic brain volumes (sexually dimorphic nucleus of the preoptic area (SDN-POA) and anteroventral periventricular (AVPV) nucleus) are influenced by estrogens. Phytoestrogens, derived from plants (especially soy products), are molecules structurally and functionally similar to estradiol. The purpose of this study was to examine: the consumption of phytoestrogen (using a phytoestrogen-rich (Phyto-600) versus a phytoestrogen-free (Phyto-free)) diets from conception to adulthood (or changing the diets during adulthood) and characterizing (a) circulating plasma phytoestrogen levels, (b) testosterone levels in males, (c) sexually dimorphic brain volumes (i.e. the SDN-POA and AVPV) and (d) the presence of apoptotic cells in these brain structures in Long-Evans rats. Phyto-600 fed animals displayed total serum phytoestrogens levels 37-fold higher compared to Phyto-free values. Circulating testosterone levels were not significantly altered by the diets. Female SDN-POA volumes were not altered by the diets. Whereas, males fed a Phyto-free diet displayed decreased SDN-POA volumes compared to male Phyto-600 values. Females fed the Phyto-600 diet displayed larger AVPV volumes compared to males on the same diet or females on the Phyto-free diet. Males fed the Phyto-free diet had the largest AVPV values compared to Phyto-600 fed males. When the SDN-POA region was examined in lifelong Phyto-free fed males, apoptotic cells were present versus males fed the Phyto-600 diet and in the AVPV region the opposite results were obtained. In summary, consumption of dietary phytoestrogens (estrogen mimics) can alter hormone-sensitive hypothalamic brain volumes in rodents during adulthood.

Stress (hypothalamic–pituitary–adrenal axis) and pain response in male rats exposed lifelong to high vs. low phytoestrogen diets

Estrogens exhibit complex but beneficial effects on brain structure, function and behavior. Soy-derived dietary phytoestrogens protect against hormone-dependent and age-related diseases, due to their estrogen-like hormonal actions. However, the effects of phytoestrogens on brain and behavior are relatively unknown. This study examined the influence of exposing male Long–Evans rats (lifelong) to either a phytoestrogen-rich (Phyto-600) or a phytoestrogen-free (Phyto-free) diet on body weights, behavioral pain thresholds, the hypothalamic–pituitary–adrenal (HPA) hormonal stress response, hippocampal glucocorticoid receptor and brain neural cell adhesion molecules (NCAM) and synaptophysin levels using standard behavioral and biochemical techniques. Body weights were significantly decreased in Phyto-600 fed animals compared to Phyto-free values. There were no significant changes in behavioral pain thresholds, circulating corticosterone concentrations (after acute immobilization stress) or NCAM and synaptophysin levels in various brain regions by the diet treatments. However, Phyto-600 fed males displayed significantly higher plasma adrenocorticotrophin (ACTH) (post-stress) and hippocampal glucocorticoid receptor levels vs. Phyto-free values. These data suggest that (1) body weights are significantly reduced by soy-derived phytoestrogens, (2) behavioral pain thresholds (via heat stimuli) are not influenced by dietary phytoestrogens, but (3) these estrogenic molecules in the hippocampus enhance glucocorticoid receptor abundance and alter the negative feedback of stress hormones towards a female-like pattern of higher ACTH release after activation of the HPA stress axis. This study is the first to show that lifelong consumption of dietary phytoestrogens alters the HPA stress response in male rats.

Intake of Dietary Phytoestrogens by Dutch Women

Higher consumption of phytoestrogens might be protective against certain chronic diseases. Accurate quantification of habitual phytoestrogen intake is important for assessing associations between phytoestrogens and risk for certain diseases. The aim of this study was to estimate dietary intake of phytoestrogens in Dutch middle-aged and elderly women and to describe their main sources. Women were recruited between 1993 and 1997 and aged 50-69 y at enrollment (Prospect-EPIC; n = 17,357). A detailed food frequency questionnaire referring to the preceding year was filled in at recruitment. A literature search was conducted to obtain data regarding content of the isoflavones daidzein, genistein, formononetin, biochanin A, the coumestan coumesterol and the lignans matairesinol and secoisolariciresinol in relevant food items. Concentrations of each phytoestrogen in each food item were subsequently grouped by seven categories; group scores were multiplied by daily intakes of food items and then summed across food items to produce for each participant a total daily intake score for each phytoestrogen. Approximately 75% of participants were postmenopausal at recruitment. The mean age was 57 y. Geometric means of daily intake of daidzein, genistein, formononetin, biochanin A, coumesterol, matairesinol and secoisolariciresinol were 0.15, 0.16, 0.08, 0.001, <0.001, 0.07 and 0.93 mg, respectively. The main sources for isoflavones were peas and beans, nuts, grain products, coffee, tea and soy products. The main sources for coumestans were peas, beans and other vegetables. The main sources of lignans were grain products, fruit and alcoholic beverages (red and white wines). We conclude that intake levels of phytoestrogen in our study population are low; however, they are comparable with intake levels previously reported for other Western cohorts. In this population, phytoestrogen intake consisted largely of lignans.

Phytoestrogens and Mycoestrogens Bind to the Rat Uterine Estrogen Receptor

Consumption of phytoestrogens and mycoestrogens in food products or as dietary supplements is of interest because of both the potential beneficial and adverse effects of these compounds in estrogen-responsive target tissues. Although the hazards of exposure to potent estrogens such as diethylstilbestrol in developing male and female reproductive tracts are well characterized, less is known about the effects of weaker estrogens including phytoestrogens. With some exceptions, ligand binding to the estrogen receptor (ER) predicts uterotrophic activity. Using a well-established and rigorously validated ER-ligand binding assay, we assessed the relative binding affinity (RBA) for 46 chemicals from several chemical structure classes of potential phytoestrogens and mycoestrogens. Although none of the test compounds bound to ER with the affinity of the standard, 17beta-estradiol (E(2)), ER binding was found among all classes of chemical structures (flavones, isoflavones, flavanones, coumarins, chalcones and mycoestrogens). Estrogen receptor relative binding affinities were distributed across a wide range (from approximately 43 to 0.00008; E(2) = 100). These data can be utilized before animal testing to rank order estimates of the potential for in vivo estrogenic activity of a wide range of untested plant chemicals (as well as other chemicals) based on ER binding.