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PubMed2005

Fetal exposure to phytoestrogens--the difference in phytoestrogen status between mother and fetus.

The goal of this study was to investigate fetal exposure to phytoestrogens, estrogenic compounds derived from plants, by measuring serum concentrations of phytoestrogens in maternal and cord blood. This study included 51 mothers scheduled for cesarean section (C-section), to obtain the serum of mother and fetus at almost the same time. Serum concentrations of phytoestrogens, including genistein (Gen), daidzein (Dai), coumestrol (Cou), equol (Equ; a metabolite of Dai), and sulfate-conjugated Gen, were measured in maternal and cord blood samples by LC-MS/MS and HPLC. It was found that phytoestrogens were transferred from mother to fetus. The detection rates of Gen, Dai, Equ, and Cou in cord serum were 100%, 80%, 35%, and 0%, respectively. Levels of Gen and Dai were higher in cord than in maternal serum (mean=19.4 ng/ml vs.7.2 ng/ml and 4.3 ng/ml vs.1.8 ng/ml for Gen and Dai, respectively). However, a reverse pattern was seen for Equ (cord mean=0.9 ng/ml, maternal mean=2.0 ng/ml). The correlations were significant between the concentration levels of Gen and Dai, Gen and Equ, and Gen and Dai plus Equ in cord serum. However, in maternal serum, the correlations were weak. Also, in 8 of 10 cord serum samples, sulfate-conjugated Gen was detected (mean=5.2 ng/ml, standard deviation=4.7), but it was detected from only one maternal serum (8.7 ng/ml). This study demonstrates placental transfer of phytoestrogens from mother to fetus. It is suggested that the metabolic and/or excretion rates of phytoestrogens are different between mother and fetus and once phytoestrogens are transferred to the fetus, they tend to stay in the fetal side longer than in the maternal side. While the implications for the health and development of the newborn are not known, these data suggest that the effects of fetal exposure to phytoestrogens should be studied further.

Adult↗
PubMed2005

Phytoestrogen metabolites are much more active than phytoestrogens themselves in increasing prostaglandin F(2alpha) synthesis via prostaglanin F(2alpha) synthase-like 2 stimulation in bovine endometrium.

Phytoestrogens have recently been suggested to be the cause of infertility by stimulating luteolytic prostaglandin (PG) F(2alpha) secretion from endometrium in cattle. The purpose of this study was to examine the enzymatic and molecular mechanisms involved in the preferential induction of PGF(2alpha) synthesis by phytoestrogens, and whether phytoestrogens influence endometrial cell viability. Cultured bovine endometrial epithelial and stromal cells were exposed to phytoestrogens (daidzein and genistein) and their metabolites (equol and p-ethyl phenol) for 24h. Prostaglandin F(2alpha) and PGE2 were stimulated by phytoestrogens in both stromal and epithelial cells, with a preference for PGF(2alpha) synthesis in epithelial cells (P<0.001). Although RT-PCR and Western Blot analyses did not reveal the influence of phytoestrogens on either gene expression or protein level of cyclooxygenase-2 (COX-2) and PGE2 synthase (PGES) in stromal and epithelial cells (P>0.05), the stimulative effects of equol and p-ethyl phenol on PGF(2alpha) synthase-like 2 (PGFSL2) gene expression and protein level were observed only in epithelial cells (P<0.05). The same compounds did not affect PGFSL2 gene expression and protein in stromal cells (P>0.05). Exposure to phytoestrogens and their metabolites decreased cell viability in both stromal and epithelial cells. Stromal cell viability decreased to 50% of the control and was more evident than that in epithelial cells (P<0.001). The overall results suggest that infertility in cattle, caused by phytoestrogen-dependent preferential stimulation of luteolytic PGF(2alpha) synthesis, is caused by increasing PGFSL2 in epithelial cells, and by decreasing stromal cell viability, which are the main source of luteotropic PGE2 production.

Animals↗
PubMed2004

Phytoestrogen concentrations in serum and spot urine as biomarkers for dietary phytoestrogen intake and their relation to breast cancer risk in European prospective investigation of cancer and nutrition-norfolk.

Subjects of this study consisted of 333 women (aged 45-75 years) drawn from a large United Kingdom prospective study of diet and cancer, the European Prospective Investigation of Cancer and Nutrition-Norfolk study. Using newly developed gas chromatography/mass spectrometry and liquid chromatography/mass spectrometry methods incorporating triply (13)C-labeled standards, seven phytoestrogens (daidzein, genistein, glycitein, O-desmethylangolensin, equol, enterodiol, and enterolactone) were measured in 114 spot urines and 97 available serum samples from women who later developed breast cancer. Results were compared with those from 219 urines and 187 serum samples from healthy controls matched by age and date of recruitment. Dietary levels were low, but even so, mean serum levels of phytoestrogens were up to 600 times greater than postmenopausal estradiol levels. Phytoestrogen concentrations in spot urine (adjusted for urinary creatinine) correlated strongly with that in serum, with Pearson correlation coefficients > 0.8. There were significant relationships (P < 0.02) between both urinary and serum concentrations of isoflavones across increasing tertiles of dietary intakes. Urinary enterodiol and enterolactone and serum enterolactone were significantly correlated with dietary fiber intake (r = 0.13-0.29). Exposure to all isoflavones was associated with increased breast cancer risk, significantly so for equol and daidzein. For a doubling of levels, odds ratios increased by 20-45% [log(2) odds ratio = 1.34 (1.06-1.70; P = 0.013) for urine equol, 1.46 (1.05-2.02; P = 0.024) for serum equol, and 1.22 (1.01-1.48; P = 0.044) for serum daidzein]. These estimates of risk are similar to those established for estrogens and androgens in postmenopausal breast cancer but need confirmation in larger studies.

Adult↗
PubMed2005

Membranal effects of phytoestrogens and carboxy derivatives of phytoestrogens on human vascular and bone cells: new insights based on studies with carboxy-biochanin A.

Estradiol-17beta (E2) and some phytoestrogens induce a biphasic effect on DNA synthesis in cultured human vascular smooth muscle cells (VSMC), i.e., stimulation at low concentrations and inhibition at high concentrations. These compounds also increase the specific activity of creatine kinase (CK) as well as intracellular Ca2+ concentration in both VSMC and human female-derived cultured bone cells (OBs), and stimulate ERK1/2 phosphorylation in VSMC. At least some of these effects are exerted via membranal binding sites (mER), as would appear from observations that protein-bound, membrane impermeant estrogenic complexes can mimic the effect of E2 on DNA synthesis, intracellular Ca2+ concentration and MAPK, but not on CK activity. We now extend these studies by examining the effects of a novel carboxy-derivative of biochanin A, 6-carboxy-biochanin A (cBA) in VSMC and human osteoblasts in culture. cBA increased DNA synthesis in VSMC in a dose-dependent manner and was able to maintain this effect when linked to a cell membrane impermeable protein. In VSMC both cBA and estradiol, in their free or protein-bound forms induced a steep and immediate rise in intracellular calcium. Both the free and protein-bound conjugates of cBA and estradiol increased net MAPK-kinase activity. Neither the stimulatory effect of cBA nor the inhibitory effect of estradiol on DNA synthesis in VSMC could be shown in the presence of the MAPK-kinase inhibitor UO126. The presence of membrane binding sites for both estradiol and cBA was supported by direct visualization, using fluorescence labeling of their respective protein conjugates, E2-BSA and cBA-ovalbumin. Furthermore, these presumed membrane ER for estradiol and cBA were co-localized. In cultured human osteoblasts, cBA stimulated CK activity in a dose related fashion, which paralleled the increase in CK induced by estradiol per se, confirming the estrogenic properties of cBA in human bone cells. Both the free and protein-bound forms of cBA elicited immediate and substantial increments in intracellular Ca2+, similar to, but usually larger than the responses elicited by estradiol per se. cBA also increased ERalpha and suppressed ERbeta mRNA expression in human osteoblasts. Cultured human osteoblasts also harbor membrane binding sites for protein-bound form of cG, which are co-localized with the binding sites for protein-bound estradiol. The extent to which these properties of the novel synthetic phytoestrogen derivatives may be utilized to avert human vascular and/or bone disease requires further study.

Binding Sites↗
PubMed2001

Dietary soy-phytoestrogens decrease testosterone levels and prostate weight without altering LH, prostate 5alpha-reductase or testicular steroidogenic acute regulatory peptide levels in adult male Sprague-Dawley rats.

Nutritional factors, especially phytoestrogens, have been extensively studied for their potential beneficial effects against hormone-dependent and age-related diseases. The present study describes the short-term effects of dietary phytoestrogens on regulatory behaviors (food/water intake, locomotor activity and body weight), prostate weight, prostate 5alpha-reductase enzyme activity, reproductive hormone levels, and testicular steroidogenic acute regulatory peptide (StAR) levels in adult Sprague-Dawley rats. Animals were fed either a phytoestrogen-rich diet containing approximately 600 microg/g isoflavones (as determined by HPLC) or a phytoestrogen-free diet. After 5 weeks of consuming these diets, plasma phytoestrogen levels were 35 times higher in animals fed the phytoestrogen-rich vs phytoestrogen-free diets. Body and prostate weights were significantly decreased in animals fed the phytoestrogen-rich diet vs the phytoestrogen-free fed animals; however, no significant change in prostate 5alpha-reductase enzyme activity was observed between the treatment groups. Locomotor activity levels were higher in the phytoestrogen-rich vs the phytoestrogen-free animals during the course of the treatment interval. Plasma testosterone and androstenedione levels were significantly lower in the animals fed the phytoestrogen-rich diet compared with animals fed the phytoestrogen-free diet. However, there were no significant differences in plasma LH or estradiol levels between the diet groups. Testicular StAR levels were not significantly different between the phytoestrogen-rich vs the phytoestrogen-free fed animals. These results indicated that consumption of dietary phytoestrogens resulting in very high plasma isoflavone levels over a relatively short period can significantly alter body and prostate weight and plasma androgen hormone levels without affecting gonadotropin or testicular StAR levels. The findings of this study identify the biological actions of phytoestrogens on male reproductive endocrinology and provide insights into the protective effects these estrogen mimics exert in male reproductive disorders such as benign prostatic hyperplasia and prostate cancer.

Animals↗
PubMed2002

Composition, red blood cell uptake, and serum protein binding of phytoestrogens extracted from commercial kudzu-root and soy preparations.

Kudzu-root and soy phytoestrogens have been associated with anti-cancer and anti-intoxication activities. Sales of capsules containing kudzu-root and soy extracts through health food stores and the Internet are unregulated. To compare efficacy, the amount of phytoestrogens present in commercial preparations and their fate in biological samples must be determined. In this study, the levels and composition of phytoestrogens in kudzu-root and soy extracts were studied using high-performance liquid chromatography with ultraviolet light detection. The bioavailability of phytoestrogens was studied by measuring red blood cell (RBC) uptake and serum protein binding ability. Phytoestrogen levels in acidified kudzu-root samples were 5- to 10-fold greater than those in nonacidified samples. Puerarin accounted for 80% of total phytoestrogens in kudzu-root. In soy extract, puerarin was absent while genistin, glycetein, and daidzin or daidzein were the major phytoestrogens. The RBC uptake depended on the phytoestrogen's polarity and molecular length. When serum was dialyzed with phytoestrogen standards in a buffer, the protein binding of phytoestrogens correlated negatively with their polarity. However, when serum was dialyzed with kudzu-root or soy extract, almost all of the phytoestrogens present in the extract bound to serum protein. Therefore, this study suggests differences in the bioavailability of phytoestrogens when they are ingested as purified compounds compared with crude plant extract. The differential composition of phytoestrogens in kudzu-root and soy may account for the differences in their therapeutic activities.

Biological Availability↗
PubMed2005

Dietary phytoestrogens and lung cancer risk.

CONTEXT: Despite lung-specific in vitro and in vivo studies that support a chemopreventive role for phytoestrogens, there has been little epidemiologic research focused on dietary intake of phytoestrogens and risk of lung cancer. OBJECTIVE: To examine the relationship between dietary intake of phytoestrogens and risk of lung cancer. DESIGN, SETTING, AND PARTICIPANTS: Ongoing US case-control study of 1674 patients with lung cancer (cases) and 1735 matched healthy controls. From July 1995 through October 2003, participants were personally interviewed with epidemiologic and food frequency questionnaires to collect demographic information and to quantify dietary intake of 12 individual phytoestrogens. MAIN OUTCOME MEASURE: Risk of lung cancer, estimated using unconditional multivariable logistic regression analyses stratified by sex and smoking status and adjusted for established and putative lung cancer risk factors. RESULTS: Reductions in risk of lung cancer tended to increase with each increasing quartile of phytoestrogen intake. The highest quartiles of total phytosterols, isoflavones, lignans, and phytoestrogens were each associated with reductions in risk of lung cancer ranging from 21% for phytosterols (odds ratio [OR], 0.79; 95% confidence interval [CI], 0.64-0.97; P = .03 for trend) to 46% for total phytoestrogens from food sources only (OR, 0.54; 95% CI, 0.42-0.70; P<.001 for trend). Sex-specific effects were also apparent. For men, statistically significant trends for decreasing risk with increasing intake were noted for each phytoestrogen group, with protective effects for the highest quartile of intake ranging from 24% for phytosterols (OR, 0.76; 95% CI, 0.56-1.02; P = .04 for trend) to 44% for isoflavones (OR, 0.56; 95% CI, 0.41-0.76; P<.001 for trend), while in women, significant trends were only present for intake of total phytoestrogens from food sources only, with a 34% (OR, 0.66; 95% CI, 0.46-0.96; P = .01 for trend) protective effect for the highest quartile of intake. The apparent benefits of high phytoestrogen intake were evident in both never and current smokers but less apparent in former smokers. In women, statistically significant joint effects were evident between hormone therapy use and phytoestrogen intake. Specifically, high intake of the lignans enterolactone and enterodiol and use of hormone therapy were associated with a 50% (OR, 0.50; 95% CI, 0.31-0.68; P = .04 for interaction) reduction in risk of lung cancer. CONCLUSIONS: While there are limitations and concerns regarding case-control studies of diet and cancer, these data provide further support for the limited but growing epidemiologic evidence that phytoestrogens are associated with a decrease in risk of lung cancer. Confirmation of these findings is still required in large-scale, hypothesis-driven, prospective studies.

Aged↗
PubMed2001

A review of the evidence for the use of phytoestrogens as a replacement for traditional estrogen replacement therapy.

Estrogen replacement therapy (ERT) is recommended for postmenopausal women primarily for reduction of menopausal symptoms and prevention of osteoporosis and cardiovascular disease. However, only 35% to 40% of women ever start ERT, and many do not continue it. One of the reasons women are reluctant to receive postmenopausal ERT is that they perceive prescription estrogens as being "unnatural." Because of this, there is increasing interest in the use of plant-derived estrogens, also known as phytoestrogens. This article reviews the evidence for the potential of phytoestrogens, either in dietary or supplemental form, to replace traditional forms of ERT. A comprehensive search of the English-language literature identified more than 1000 articles published in the past 30 years about phytoestrogens. In total, 74 studies were selected for inclusion in this review based on relevance, inclusion of human subjects wherever possible, and study design. The studies examine phytoestrogens' inhibition of the growth of cancer cell lines in vitro and in animals. They also look at the role of phytoestrogens in the reduction of cholesterol levels, and the use of one phytoestrogen derivative, ipriflavone, in the prevention of osteoporosis. Some small studies examine the role of phytoestrogens in the prevention of menopausal symptoms. Evidence for the potential health benefits of phytoestrogens is increasing. However, the clinically proven health benefits of prescribed ERT far outweigh those of phytoestrogens. Therefore, there is insufficient evidence to recommend the use of phytoestrogens in place of traditional ERT, or to make recommendations to women about specific phytoestrogen products.

Breast Neoplasms↗
PubMed2006

Plasma and prostate phytoestrogen concentrations in prostate cancer patients after oral phytoestogen supplementation.

BACKGROUND: Phytoestrogens have been suggested to reduce the risk of prostate cancer (CaP), but no data exists on how oral phytoestrogen supplementation influences phytoestrogen concentrations in prostate tissue. METHODS: Forty men with CaP, assigned for radical prostatectomy, received 240 mg of clover phytoestrogens or placebo daily for a 2-week period before their operation in a prospective and randomized study. Phytoestrogens were measured in plasma and prostate tissue by time-resolved fluoroimmunoassay (TR-FIA). RESULTS: All patients had low baseline phytoestrogen concentrations and only 35% had a detectable plasma concentration of equol. Oral supplementation with phytoestrogens induced a statistically significant (P<0.001) 23- and 7-fold increase in prostate tissue concentrations of the phytoestrogens genistein and daidzein, respectively. Supplemented patients demonstrated prostate tissue genistein and daidzein concentrations that were over twofold higher than their plasma. Interestingly, even though the placebo group did not receive phytoestrogen challenge, they also demonstrated twofold prostate tissue genistein and daidzein concentrations compared to their plasma values, suggesting that the prostate can concentrate available phytoestrogens. In addition, after the supplementation, 90% of the supplemented patients had a detectable plasma equol concentration. CONCLUSIONS: We conclude that prostate tissue can concentrate genistein and daidzein. Significant elevation of intraprostatic genistein and daidzein concentrations can be achieved with a short-term dietary phytoestrogen supplementation.

Administration, Oral↗
PubMedDate not supplied

Neurobehavioral effects of dietary soy phytoestrogens.

Phytoestrogens, plant-derived nonsteroidal estrogens found in high abundance in most soy food products, have been studied for their potential beneficial effects against hormone-dependent cancers and age-related diseases. However, little is known about the influence of phytoestrogens on the brain or behavior. This brief review describes mainly our own studies in rodents that have examined the influence of dietary soy isoflavones on certain aspects of brain structure, learning, memory and anxiety along with the brain androgen-metabolizing enzyme, aromatase. These studies used a commercially available diet rich in phytoestrogens (Phyto-rich) vs. a custom diet relatively free of phytoestrogens (Phyto-free). The phytoestrogen content of each diet was determined by high-performance liquid chromatography analysis, circulating plasma phytoestrogen levels were quantified by gas chromatography mass spectroscopy and concentrations of phytoestrogens in specific brain regions were measured by time-resolved fluoroimmunoassay (TR-FIA). Our studies showed that brain aromatase levels were not significantly altered by phytoestrogen diet treatments in perinatal, maternal or adult rats. However, volumes of the sexually dimorphic nucleus of the preoptic area (SDN-POA) were significantly affected by the Phyto-free diet treatment in male rats during adulthood, where SDN-POA volumes were smaller compared to Phyto-rich male values. Additionally, the Phyto-rich diet fed to adult male and female rats produced anxiolytic effects as assessed in the elevated plus maze vs. Phyto-free fed animals. Finally, when learning and memory parameters were examined in a radial arm maze testing visual-spatial memory (VSM), the diet treatments significantly changed the typical sexually dimorphic pattern of VSM. Specifically, adult Phyto-rich fed females outperformed Phyto-free fed females, while in males on the same diets, the opposite pattern of maze performance was observed. When female vs. male performance was compared, Phyto-rich females executed the VSM task in a manner similar to that of Phyto-free fed males, while Phyto-free fed female's VSM was comparable to Phyto-rich males. These results indicate that consumption of dietary phytoestrogens resulting in very high plasma isoflavone levels (in many cases over a relatively short interval of consumption in adulthood) can significantly alter sexually dimorphic brain regions, anxiety, learning and memory. The findings of these studies identify the biological actions of phytoestrogens, specifically isoflavones and their metabolites, found in animal soy-containing diets on brain and behavior and implicate the importance of phytoestrogens given the recognized significance of estrogens in brain and neural disorders, such as Alzheimer's disease, especially in women.

Animals↗
PubMed2003

Phytoestrogen supplement use by women.

Phytoestrogens are weak estrogens found concentrated in soybeans. Americans consume phytoestrogens primarily in traditional soy foods, soymilk and isolated soy protein added during food processing or consumed as a beverage. Extracted phytoestrogens are also marketed in numerous forms as dietary supplements regulated under the Dietary Supplement Health and Education Act. Consumers of phytoestrogen supplements tend to be peri- and postmenopausal women looking for an alternative to hormone therapy. Although there are no approved health claims for phytoestrogens at this time, numerous claims are being made regarding benefits to heart, bone, breast and general menopausal health. The data supporting these claims are generally not strong. The strongest data show that phytoestrogens reduce the number and intensity of hot flashes, although the reduction is a modest 10-20%. The studies showing cholesterol lowering have used soy protein rather than phytoestrogen extracts. The soy protein appears to be required for this effect, although phytoestrogen extracts may have other beneficial effects on the cardiovascular system. The data on bone metabolism are suggestive of possible benefits whereas the effects on the breast are the most poorly understood. Although most animal studies have shown cancer-preventive effects, a few recent studies suggest that soy phytoestrogens may stimulate breast cancer cell growth under certain circumstances. Before recommendations regarding phytoestrogen supplements can be safely made, we must have more information on the effects of the extracts on bone, heart and breast health. Until safety with respect to breast cancer is established, phytoestrogen supplements should not be recommended, particularly for women at high risk of breast cancer.

Animals↗
PubMed2003

The OECD program to validate the rat uterotrophic bioassay. Phase 2: dietary phytoestrogen analyses.

Many commercial laboratory diets have detectable levels of isoflavones (e.g., phytoestrogens such as genistein [GN]) that have weak estrogenic activity both in vitro and in vivo. During validation studies of the uterotrophic bioassay, diet samples from 20 participating laboratories were collected and analyzed for three major phytoestrogens: GN, daidzein (DN), and coumestrol (CM). Soy phytoestrogens GN and DN were found at total phytoestrogen levels from 100 to 540 microg/g laboratory diet; a forage phytoestrogen, CM, ranged from nondetectable to 4 microg/g laboratory diet. The phytoestrogen levels were compared with both baseline uterine weights of the control groups and with the relative uterine weight increase of groups administered two weak estrogen agonists: bisphenol A (BPA) and nonylphenol (NP). The comparison uses a working assumption of additivity among the phytoestrogens, despite several significant qualifications to this assumption, to estimate total genistein equivalents (TGE). Some evidence was found that phytoestrogen levels in the diet > 325-350 microg/g TGE could diminish the responsiveness of the uterotrophic bioassay to weak agonists. This was especially true for the case of the intact, immature female version of the uterotrophic bioassay, where higher food consumption relative to body weight leads to higher intakes of dietary phytoestrogens versus ovariectomized adults. This dietary level is sufficient in the immature female to approach a biological lowest observable effect level for GN of 40-50 mg/kg/day. These same data, however, show that low to moderate levels of dietary phytoestrogens do not substantially affect the responsiveness of the assay with weak estrogen receptor agonists such as NP and BPA. Therefore, laboratories conducting the uterotrophic bioassay for either research or regulatory purposes may routinely use diets containing levels of phytoestrogens < 325-350 microg/g TGE without impairing the responsiveness of the bioassay.

Administration, Oral↗
PubMed1998

Phytoestrogens and human health effects: weighing up the current evidence.

Phytoestrogens are naturally occurring plant compounds which have oestrogenic and/or anti-oestrogenic activity. They are present in many human foodstuffs including beans, sprouts, cabbage, spinach, soyabean, grains and hops. The main classes are the isoflavones, coumestans and lignans. This review assesses the evidence that these substances may have adverse and/or beneficial impacts on the risk of several hormone-dependent diseases in humans. Evidence from studies of various animal species has demonstrated that ingestion of high levels of phytoestrogens can produce adverse effects on reproductive endpoints including fertility. Studies in laboratory animals have also shown that exposure to high doses of phytoestrogens during development can adversely affect brain differentiation and reproductive development in rodents, but may also have possible beneficial effects. In humans, there is a lack of information concerning the possible effects of high doses of phytoestrogens in infants and this should be addressed as a matter of priority so that any risks (or benefits) can be established. In adults, no current data exist to suggest that consumption of phytoestrogens at the levels normally encountered in the diet is likely to be harmful. Epidemiological studies suggest that foodstuffs containing phytoestrogens may have a beneficial role in protecting against a number of chronic diseases and conditions. For cancer of the prostate, colon, rectum, stomach and lung, the evidence is most consistent for a protective effect resulting from a high intake of grains, legumes, fruits and vegetables; it is not possible to identify particular food types or components that may be responsible. Dietary intervention studies indicate that in women soya and linseed may have beneficial effects on the risk of breast cancer and may help to alleviate postmenopausal symptoms. For osteoporosis, tentative evidence suggests phytoestrogens may have similar effects in maintaining bone density to those of the related pharmaceutical compound ipriflavone. Soya also appears to have beneficial effects on blood lipids which may help to reduce the risk of cardiovascular disease and atherosclerosis. Generally, however, little evidence exists to link these effects directly to phytoestrogens; many other components of soya and linseed are biologically active in various experimental systems and may be responsible for the observed effects in humans. It is concluded that dietary phytoestrogens may have a role in the prevention of several types of chronic disease including certain cancers. However, at present the evidence is not sufficient to recommend particular dietary practices or changes. Encouraging findings from laboratory and clinical studies indicate the need for further research to clarify the biological activities of phytoestrogens in humans.

Adult↗
PubMed2000

Phytoestrogens decrease brain calcium-binding proteins but do not alter hypothalamic androgen metabolizing enzymes in adult male rats.

Phytoestrogen [plant estrogenic-like molecule(s)] research has grown rapidly in recent years due to their potential health benefits. However, little is known about phytoestrogen's effects on the CNS. Androgen metabolizing enzymes are known to regulate neuroendocrine functions and reproductive behaviors, while calcium-binding proteins are associated with protecting against neurodegenerative diseases. Therefore, we examined aromatase and 5alpha-reductase enzyme activities in the medial basal hypothalamic and preoptic area (mbh-poa) and characterized mbh-poa and amygdala (amy) calbindin and calretinin levels (via Western analysis) from animals fed a phytoestrogen-free (P-free) vs. a phytoestrogen-containing diet [(P-600); that had 600 microg/g of phytoestrogens]. After approximately 5 weeks on the diets, the male rats were killed at 105 days. P-600 plasma phytoestrogen levels were 78-fold higher than the P-free values and the mbh-poa phytoestrogen content was 8-fold higher than the P-free group, demonstrating the passage of phytoestrogens into brain. In general, brain aromatase or 5alpha-reductase activity levels were not significantly altered by the experimental diets. However, independent of brain site (i.e., mbh-poa or amy) the abundance of calbindin from male P-600 rats was significantly lower than P-free animals. Conversely, for calretinin there were no significant alterations in the mbh-poa tissue site, while in the amy a similar pattern of expression was seen to that of the calbindin results. These data suggest that consumption of phytoestrogens via a soy diet for a relatively short interval can significantly: (1) elevate plasma and brain phytoestrogens levels and (2) decrease brain calcium-binding proteins without altering brain androgen metabolizing enzymes.

Androgens↗
PubMed2003

A randomized placebo-controlled crossover trial with phytoestrogens in treatment of menopause in breast cancer patients.

OBJECTIVE: Phytoestrogens are popular in treatment of menopause, although scientific evidence is insufficient as to their efficacy. We studied the effects of daily use of isoflavonoids on climacteric symptoms and quality of life in patients with a history of breast cancer. METHODS: Sixty-two postmenopausal symptomatic women were randomized to use either phytoestrogen (tablets containing 114 mg of isoflavonoids) or a placebo for 3 months; the treatment regimens were reversed after a 2-month washout period. Fifty-six women completed the study. Menopausal symptoms were recorded on the Kupperman index and the visual analogue scale, and working capacity and mood changes were assessed via validated questionnaires. In addition, we followed the levels of phytoestrogens, follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol, and sex hormone-binding globulin. Liver enzymes and creatinine were also assessed at each visit. RESULTS: The phytoestrogen regimen raised the circulating levels of phytoestrogens (daidzein, genistein, equol) 19- to 106-fold. The Kupperman index was reduced by 4.2 +/- 9.6 (mean +/- standard deviation) (15.5%) during phytoestrogen use and similarly by 4.0 +/- 8.1 (14.7%) during placebo use (P nonsignificant). The quality of life parameters (working capacity, mood changes) were unaffected by phytoestrogen. In addition, the phytoestrogen regimen caused no changes in FSH, LH, estradiol, or sex hormone-binding globulin. Phytoestrogen treatment was well tolerated and caused no changes in liver enzymes, creatinine, body mass index, or blood pressure. Of the 56 women, 25 (44.6%) preferred the phytoestrogen regimen, 15 preferred the placebo (26.8%), and 16 (28.6%) reported no preference (nonsignificant). CONCLUSION: Pure isoflavonoids did not alleviate subjective menopausal symptoms in breast cancer patients.

Breast Neoplasms↗
PubMed2002

The correlation between dietary soy phytoestrogens and neuropathic pain behavior in rats after partial denervation.

UNLABELLED: Soy diets suppress the development of neuropathic pain behavior in rats undergoing partial sciatic nerve ligation (PSL) injury. Phytoestrogens, plant isoflavones and lignans, abundantly found in soy products, have powerful estrogenic properties. Because, in some preparations, steroid estrogens were found to exert antinociception, we examined whether the analgesic effect of dietary soy is mediated by phytoestrogens. Male Wistar rats were fed five different diets containing 8-180 microg of phytoestrogens per gram. These diets were administered 2 wk before and 2 wk after PSL injury. Levels of tactile allodynia and mechanical and heat hyperalgesia of these rats were determined on Days 3, 8, and 14 after PSL injury. Plasma levels of two major phytoestrogens (genistein and daidzein) and two daidzein metabolites (equol and dihydrodaidzein) were assessed on Day 14 postoperatively. We found that the plasma concentration of these phytoestrogens and the levels of allodynia and hyperalgesia varied highly among dietary groups. Average plasma concentrations of phytoestrogens were associated with reduced levels of tactile allodynia and mechanical hyperalgesia, but not with reduced heat allodynia. Low and high plasma phytoestrogen levels were not analgesic in these tests. This report is the first to show that, at certain plasma concentrations, phytoestrogens reduce neuropathic pain in rats. IMPLICATIONS: Dietary soy suppresses neuropathic pain in rats after partial sciatic nerve ligation. Some of the pain-suppression properties of soy can be attributed to phytoestrogens, isoflavones abundantly found in soy products. Average, but not low or high, plasma levels of phytoestrogens are associated with analgesia.

Analgesics↗