Decreased serum estradiol concentration associated with high dietary intake of soy products in premenopausal Japanese women

The role of soy and soy isoflavones on women's fertility and related outcomes: an update

Soy is a key food in human nutrition. It is widely used in eastern traditional cuisine and it has recently diffused among self-conscious and vegetarian diets. The success of soy mainly depends on versatility and supposed healthy properties of soy foods and soy components. Meanwhile, the possible influence on endocrine system, in particular by isoflavones, raised concerns among some researchers. The present paper aims to conduct a review of available data on the effect of soy, soy foods and soy components on women's fertility and related outcomes. Eleven interventional studies, eleven observational studies and one meta-analysis have been selected from the results of queries. A weak, not clinically relevant effect has been highlighted on cycle length and hormonal status. However, a suggestive positive influence has been shown among women with fertility issues and during assisted reproductive technologies. Overall, soy and soy components consumption do not seem to perturb healthy women's fertility and can have a favourable effect among subjects seeking pregnancy. However, because of the paucity of studies exploring the impact of soy intake on women's fertility, as well as the limited population sample size, the frequently incomplete specimens’ collection to investigate all cycle phases and the insufficient characterisation of participants, the evidence is suggestive and it needs further in-depth research taking into account all these aspects.

Supplementation of Estradiol Into Semen Extender Improved Goat Sperm Cryopreservation

Estradiol is a steroid hormone excreted from the female gonads, mainly during the pre-estrus. However, the potential effects of estradiol are yet to be explored on sperm parameters through cryopreservation. In this study, we supplemented estradiol, 3 and 5 μM, in the goat semen extender and assessed the sperm parameters after a freeze-thawing process. Sperm motility was assessed using the computer-assisted sperm analysis system. Sperm viability and membrane integrity improved using both 3 and 5 μM concentrations of estradiol. The highest rate of progressive motility was observed in the 3 μM estradiol group. However, a higher concentration of estradiol (5 μM) reduced the progressive motility. Then, we were interested to see if the supportive effect of estradiol on sperm motility is mediated through the intracellular concentration of calcium ionophore. We supplemented the semen extender with 1 and 10 mM ethylenediaminetetraacetic acid (EDTA) and showed that 1 mM has no adverse effect on progressive sperm motility. Then, estradiol (3 μM) was supplemented with or without EDTA (1 mM) into the semen extender. Individual EDTA treatment improved the progressive sperm motility compared to the control group. However, in the presence of estradiol, EDTA treatment reduced the progressive motility compared to the individual estradiol group. This indicated a considerable interaction between estradiol and EDTA for progressive sperm motility. Indeed, EDTA reduced the supportive effects of estradiol on sperm cryopreservation parameters. These results indicated that induction of higher progressive sperm motility in response to estradiol is a calcium-dependent process, as the EDTA did completely abrogate the estradiol-mediated effect.

Supplementing daidzein in diets improves the reproductive performance, endocrine hormones and antioxidant capacity of multiparous sows

Certain hormones play important roles in modulating mammalian reproductive behaviour. Daidzein is a well-known isoflavonic phytoestrogen that possesses oestrogenic activity. This study was conducted to probe the effects of daidzein supplementation in gestation diets on the reproductive performance in sows. A total of 120 multiparous sows (Landrace × Yorkshire) were randomly assigned to 2 groups (n = 60) and fed either a base diet (control) or one containing 200 mg/kg daidzein during gestation. We discovered that daidzein supplementation significantly increased the total number of piglets born per litter and number of piglets born alive per litter (P < 0.05), decreased the farrowing time (P < 0.05) and increased the serum oestrogen and progesterone concentrations (P < 0.05) at 35 d of gestation. Moreover, serum immunoglobulin G (IgG) concentration and superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities were higher in the daidzein-treated group than in the control group at 35 d of gestation (P < 0.05). Daidzein increased the serum SOD activity and total anti-oxidative capacity (T-AOC) at 85 d of gestation (P < 0.05). Interestingly, daidzein elevated the expression levels of the sodium-coupled neutral amino acid transporter 1 (SLC38A1) and insulin-like growth factor 1 (IGF-1) genes in the placenta (P < 0.05). These results suggest that daidzein ingestion could improve sow reproductive performance by changing serum hormones, elevating anti-oxidative capacity and up-regulating critical functional genes in the placenta.

Strategies to achieve significant physiological concentrations of bioactive phytoestrogens in plasma

The benefits to health attributed to the intake of phytoestrogens (PEs) have been demonstrated in previous studies with significant physiological concentrations of bioactive PEs, such as genistein, equol, enterolignans and urolithins in plasma. However, the achievement of high bioactive PE levels in plasma is restricted to a select population group, mainly due to the low intake of plant PEs and/or the absence, or inhibition, of the microbiota capable of producing these bioactive forms. In this study, the intake of plant PEs, the concentration of bioactive PEs in plasma, the ability of the intestinal microbiota to produce bioactive PEs, as well as the different mechanisms used by GRAS bacteria to increase the level of bioactive PEs were evaluated concluding that the use of GRAS bacteria bioactive PE producers and the development of fermented foods enriched in bioactive PEs in addition to a high intake of plant PEs and taking care of the intestinal microbiota, are some of the different strategies to achieve significant physiological concentrations of bioactive PEs in the intestine and, subsequently, in plasma and targets organs which are essential to improve menopausal symptoms or reduce the risk of some pathologies such as breast and colon cancer, or cardiovascular disease.

Urinary Isoflavones Levels in Relation to Serum Thyroid Hormone Concentrations in Female and Male Adults in the U.S. General Population

Isoflavones are phytoestrogens found in plant-based foods and nutritional supplements. Experimental studies show a positive association between isoflavones and hypothyroidism, but epidemiological findings are conflicting. We used multivariable linear regression to examine the association between urinary isoflavone concentrations and serum thyroid hormone concentrations in the National Health and Nutrition Examination Survey (2007-2010). In this study, we found that Daidzein and O-DMA associations with free T4 were stronger among women: a 10-fold increase in daidzein was associated with a 3.2% (95% CI: 1.9%, 4.5%) increase in women and a 0.6% (95% CI: -1.7%, 0.6%) decrease in men and a 10-fold increase in O-DMA was related to a 2.0% (95% CI: 1.1%, 2.9%) increase in women and a 0.3% (95% CI: -1.2%, 0.5%) decrease in men. In this study, selected urinary isoflavone concentrations were associated with serum thyroid hormone concentration in a sex-dependent fashion.

The association of urinary estrogen levels with urinary isoflavone levels: Difference between premenopausal women and postmenopausal women

Results of studies on the associations of soy food intake with urinary estrogen levels in premenopausal women and in postmenopausal women have been inconsistent. We examined the associations of urinary isoflavone levels as well as soy food intake with estrone (E1) and estradiol (E2) in pre- and postmenopausal women. In addition, we compared the levels of isoflavones, E1 and E2 across current hormone users such as those receiving hormone replacement therapy and those using oral contraceptives and non-users among both pre- and postmenopausal women. Urinary levels of isoflavones, E1 and E2 in 498 women (36 hormone users and 462 non-users) were analyzed. Premenopausal women with a higher frequency of soy food intake had higher urinary isoflavone levels, but there were no significant associations between E1 and E2 levels and urinary isoflavone levels. Levels of E1 and E2 in hormone users were significantly lower than those in hormone non-users among premenopausal women, but levels of E1 and E2 in hormone users were significantly higher than those in hormone non-users among postmenopausal women. Postmenopausal women with a higher frequency of soy food intake had higher urinary isoflavone levels, and postmenopausal women with high urinary isoflavone levels had significantly higher E1 and E2 levels. In conclusion, the associations of urinary isoflavone levels with urinary estrogen levels differed with menopausal status. Urinary levels of E1 and E2 were high in postmenopausal women with high urinary isoflavone levels but not in premenopausal women with high urinary isoflavone levels.

Application of the estrogen threshold hypothesis to the physiologic hypoestrogenemia of lactation

OBJECTIVE

This study determined the impact of breastfeeding on hypoestrogenic symptoms among women in the postpartum period and correlated these findings with the Estrogen Threshold Hypothesis, which postulates that the hypoestrogenic symptoms experienced are related to circulating estrogen levels.

STUDY DESIGN

Using a survey instrument that combined previously validated assessments of postpartum mood changes and menopausal symptoms, women were evaluated in the immediate postpartum period, prior to hospital discharge, and at 3 and 6 weeks postpartum. Each time period was analyzed independently, in a cross-sectional design, where women were categorized as "breastfeeding" or "bottle feeding."

RESULTS

Of 236 women recruited, 171 (72.5%) intended to breastfeed, and 62 (26.3%) intended to bottle feed. At both the 3- and 6-week postpartum evaluations, a similar percentage of women in the breastfeeding and bottle-feeding groups reported hot flashes. However, breastfeeding women were more likely to report vaginal dryness than those who did not breastfeed: 20/150 (13.3%) versus 3/80 (3.8%) at 3 weeks, p<0.05; 25/143 (17.5%) versus 2/87 (2.3%) at 6 weeks, p<0.001.

CONCLUSIONS

The Estrogen Threshold Hypothesis accurately predicts the findings of increased reported vaginal dryness but not hot flashes during lactation.

Withdrawal of dietary phytoestrogens in adult male rats affects hypothalamic regulation of food intake, induces obesity and alters glucose metabolism

The absence of phytoestrogens in the diet during pregnancy has been reported to result in obesity later in adulthood. We investigated whether phytoestrogen withdrawal in adult life could alter the hypothalamic signals that regulate food intake and affect body weight and glucose homeostasis. Male Wistar rats fed from conception to adulthood with a high phytoestrogen diet were submitted to phytoestrogen withdrawal by feeding a low phytoestrogen diet, or a high phytoestrogen-high fat diet. Withdrawal of dietary phytoestrogens increased body weight, adiposity and energy intake through an orexigenic hypothalamic response characterized by upregulation of AGRP and downregulation of POMC. This was associated with elevated leptin and T4, reduced TSH, testosterone and estradiol, and diminished hypothalamic ERα expression, concomitant with alterations in glucose tolerance. Removing dietary phytoestrogens caused manifestations of obesity and diabetes that were more pronounced than those induced by the high phytoestrogen-high fat diet intake.

Diverse effects of phytoestrogens on the reproductive performance: cow as a model

Phytoestrogens, polyphenolic compounds derived from plants, are more and more common constituents of human and animal diets. In most of the cases, these chemicals are much less potent than endogenous estrogens but exert their biological effects via similar mechanisms of action. The most common source of phytoestrogen exposure to humans as well as ruminants is soybean-derived foods that are rich in the isoflavones genistein and daidzein being metabolized in the digestive tract to even more potent metabolites-para-ethyl-phenol and equol. Phytoestrogens have recently come into considerable interest due to the increasing information on their adverse effects in human and animal reproduction, increasing the number of people substituting animal proteins with plant-derived proteins. Finally, the soybean becomes the main source of protein in animal fodder because of an absolute prohibition of bone meal use for animal feeding in 1995 in Europe. The review describes how exposure of soybean-derived phytoestrogens can have adverse effects on reproductive performance in female adults.

The effects of diet on circulating sex hormone levels in men

There is considerable epidemiological evidence that a Western-style diet may increase the risk of certain hormone-dependent conditions in men via its effects on hormone metabolism. Experimental evidence also suggests that dietary factors may exert subtle effects on hormone metabolism. Here we review the clinical and epidemiological evidence that diet is associated with circulating sex hormone levels in men. In comparison with factors such as age and BMI, nutrients do not appear to be strong determinants of sex hormone levels. Dietary intervention studies have not shown that a change in dietary fat and/or dietary fibre intake is associated with changes in circulating sex hormone concentrations over the short term. The data on the effects of dietary phyto-oestrogens on sex hormone levels in men are too limited for conclusions to be drawn. Observational studies between men from different dietary groups have shown that a vegan diet is associated with small but significant increases in sex-hormone-binding globulin and testosterone concentrations in comparison with meat-eaters. However, these studies have not demonstrated that variations in dietary composition have any long-term important effects on circulating bioavailable sex hormone levels in men. This lack of effect may be partly explained by the body's negative feedback mechanism, which balances out small changes in androgen metabolism in order to maintain a constant level of circulating bioavailable androgens. It appears, therefore, that future studies should look for dietary effects on the feedback mechanism itself, or on the metabolism of androgens within the target tissues.

Soy intake and urinary sex hormone levels in preschool Japanese children

The authors investigated whether soy intake is associated with sex steroid levels in Japanese children. This cross-sectional study was conducted in autumn 2006. Subjects were substantially healthy preschoolers, 230 boys and 198 girls, aged 3-6 years. Dietary data, including soy intake, were assessed using 3-day dietary records. Each child's dietary intake was controlled for total energy intake using the Willett method (Nutritional Epidemiology. Oxford, United Kingdom: Oxford University Press; 1990:245-271). Urinary estrone, estradiol, testosterone, and 5-androstene-3β,17α diol levels measured using liquid chromatography-electrospray ionization tandem mass spectrometry, and urinary dehydroepiandrosterone level measured with a radioimmunoassay, were adjusted for urinary creatinine levels. In the analysis of covariance for sex steroids after adjustments for age and body mass index, soy intake was significantly negatively related to estrone and estradiol in boys and positively related to testosterone and 5-androstene-3β,17α diol in girls. Isoflavone had a significant tendency to be negatively associated with estradiol in boys and to be positively associated with testosterone in girls. Total energy intake was not associated with any sex steroids in boys or girls. These results suggest that soy intake might affect the secretion or metabolism of sex steroids in childhood and that the effects might differ by sex.

Impairment of ovarian function and associated health-related abnormalities are attributable to low social status in premenopausal monkeys and not mitigated by a high-isoflavone soy diet

BACKGROUND

Psychological stress may impair premenopausal ovarian function and contribute to risk for chronic disease. Soy isoflavones may also influence ovarian function and affect health. Here, we report the effects of a psychological stressor (subordinate social status) and dietary soy on reproductive function and related health indices in female monkeys. We hypothesized that reproductive compromise and adverse health outcomes would be induced in subordinate when compared with dominant monkeys and be mitigated by exposure to soy.

METHODS

Subjects were 95 adult cynomolgus monkeys (Macaca fascicularis) housed in social groups of five or six. Animals consumed a soy-free, animal protein-based diet during an 8-month Baseline phase and then, during a 32-month Treatment phase, consumed either the baseline diet or an identical diet that substituted high-isoflavone soy protein for animal protein.

RESULTS

Across more than 1200 menstrual cycles, subordinate monkeys consistently exhibited ovarian impairment [increased cycle length (P < 0.02) and variability (P < 0.02) and reduced levels of progesterone (P < 0.04) and estradiol (P < 0.04)]. Subordinate status was confirmed behaviorally and was associated with elevated cortisol (P < 0.04) and relative osteopenia (P < 0.05). Consumption of the soy diet had no significant effects.

CONCLUSIONS

(i) Psychological stress adversely affects ovarian function and related health indices in a well-accepted animal model of women's health; (ii) Similar effects may extend to women experiencing reproductive impairment of psychogenic origin; (iii) soy protein and isoflavones neither exacerbate nor mitigate the effects of an adverse psychosocial environment; and (iv) this study was limited by an inability to investigate the genetic and developmental determinants of social status.

Inhibition of cancer cell invasion and metastasis by genistein

Genistein is a small, biologically active flavonoid that is found in high amounts in soy. This important compound possesses a wide variety of biological activities, but it is best known for its ability to inhibit cancer progression. In particular, genistein has emerged as an important inhibitor of cancer metastasis. Consumption of genistein in the diet has been linked to decreased rates of metastatic cancer in a number of population-based studies. Extensive investigations have been performed to determine the molecular mechanisms underlying genistein's antimetastatic activity, with results indicating that this small molecule has significant inhibitory activity at nearly every step of the metastatic cascade. Reports have demonstrated that, at high concentrations, genistein can inhibit several proteins involved with primary tumor growth and apoptosis, including the cyclin class of cell cycle regulators and the Akt family of proteins. At lower concentrations that are similar to those achieved through dietary consumption, genistein can inhibit the prometastatic processes of cancer cell detachment, migration, and invasion through a variety of mechanisms, including the transforming growth factor (TGF)-beta signaling pathway. Several in vitro findings have been corroborated in both in vivo animal studies and in early-phase human clinical trials, demonstrating that genistein can both inhibit human cancer metastasis and also modulate markers of metastatic potential in humans, respectively. Herein, we discuss the variety of mechanisms by which genistein regulates individual steps of the metastatic cascade and highlight the potential of this natural product as a promising therapeutic inhibitor of metastasis.

Soy product and isoflavone intake and breast cancer risk defined by hormone receptor status

The association between soy food consumption and breast cancer risk has been inconsistent. A hospital-based case-control study was conducted to assess the relationship between soy food intake and breast cancer risk according to the estrogen receptor (ER) and/or progesterone receptor (PR) status of breast cancer in Chinese women residing in Guangdong province from June 2007 to August 2008. A total of 438 consecutively recruited cases with primary breast cancer were frequency matched to 438 controls by age (5-year interval) and residence (rural/urban). Dietary intake was assessed by face-to-face interviews using a validated food frequency questionnaire. Odds ratios (OR) and 95% confidence intervals (CI) were obtained by using multiple unconditional logistic regression adjusted for the potential confounders. We observed a statistically significant inverse association between soy isoflavone and soy protein intake with breast cancer risk. The multivariate ORs (95% CIs) of breast cancer risk for the highest quartile compared with the lowest quartile were 0.54 (0.34-0.84) for soy isoflavone and 0.62 (0.40-0.96) for soy protein, respectively. A preventive effect of soy food was found for all subtypes of ER and/or PR status of breast cancer. The inverse association was more evident among premenopausal women. This study suggests that consumption of soy food, soy isoflavone, is inversely associated with the risk of breast cancer. The protective effects of soy did not seem to differ by ER and PR breast cancer status.

Soy intake is associated with increased 2-hydroxylation and decreased 16alpha-hydroxylation of estrogens in Asian-American women

INTRODUCTION

In Asian and Asian-American women, soy consumption is associated with reduced breast cancer risk, perhaps due to its effects on estrogen production or metabolism. In a sample of Asian-American women, we investigated the associations of usual adult soy intake with the urinary concentrations of 15 estrogens and estrogen metabolites (EM) measured using liquid chromatography-tandem mass spectrometry.

METHODS

Participants included 430 Chinese-American, Japanese-American, and Filipino-American women, ages 20 to 55 years, and living in San Francisco-Oakland (California), Los Angeles (California), or Oahu (Hawaii). They were postmenopausal (n = 167) or premenopausal in luteal phase (n = 263) when 12-hour urine samples were collected. Robust linear regression was used to assess soy tertiles as predictors of log-transformed EM measures. Individual and grouped EM were considered as concentrations (pmol/mg creatinine) and as percentages of total EM (%EM).

RESULTS

Factor analysis confirmed that EM groups defined by metabolic pathways appropriately captured covariation in EM profiles. Total EM concentrations were not significantly associated with soy in premenopausal or postmenopausal women. Among all women, %2-hydroxylated EM and %4-hydroxylation pathway EM were 16% higher (P(trend) = 0.02) and 19% higher (P(trend) = 0.03) in the highest versus lowest soy tertiles, respectively. In contrast, 16% hydroxylated EM were 11% lower (P(trend) < 0.01). Results were consistent across ethnic and menopausal groups and after adjustment for westernization measured by birthplace (Asia or United States).

DISCUSSION

Findings suggest that regular soy intake is associated with increased ratios of 2:16-pathway EM and with higher relative levels of 4-hydroxylated EM. The observed variations in estrogen metabolism might modify breast cancer risk.

Adolescent and adult soy food intake and breast cancer risk: results from the Shanghai Women's Health Study

BACKGROUND

Soy food is a rich source of isoflavones--a class of phytoestrogens that has both antiestrogenic and anticarcinogenic properties.

OBJECTIVE

The objective was to evaluate the association of adolescent and adult soy food intake with breast cancer risk in a cohort of 73,223 Chinese women who participated in the Shanghai Women's Health Study.

DESIGN

A validated food-frequency questionnaire was used to assess usual dietary intake during adulthood and adolescence. After a mean follow-up of 7.4 y, 592 incident cases of breast cancer were identified for longitudinal analyses by using Cox regressions.

RESULTS

Adult soy food consumption, measured either by soy protein or isoflavone intake, was inversely associated with the risk of premenopausal breast cancer, and the association was highly statistically significant (P for trend < 0.001). The multivariate-adjusted relative risks (RRs) for the upper intake quintile compared with the lowest quintile were 0.41 (95% CI: 0.25, 0.70) for soy protein intake and 0.44 (95% CI: 0.26, 0.73) for isoflavone intake. High intake of soy foods during adolescence was also associated with a reduced risk of premenopausal breast cancer (RR: 0.57; 95% CI: 0.34, 0.97). Women who consumed a high amount of soy foods consistently during adolescence and adulthood had a substantially reduced risk of breast cancer. No significant association with soy food consumption was found for postmenopausal breast cancer.

CONCLUSION

This large, population-based, prospective cohort study provides strong evidence of a protective effect of soy food intake against premenopausal breast cancer.

Isoflavone consumption and subsequent risk of hepatocellular carcinoma in a population-based prospective cohort of Japanese men and women

The incidence of hepatocellular carcinoma (HCC) is much higher in men than in women. Several experiment and epidemiological studies have suggested that estrogen might play an inhibitory role in the development of HCC. Because isoflavones have a similar structure as 17beta-estradiol and appear to have an anti-estrogenic effect in women and estrogenic effect in men, we hypothesized that the effect of isoflavones on HCC differs by sex. We investigated the association between isoflavones (genistein and daidzein) and soy products and HCC in Japan in a population-based prospective study in 19,998 Japanese (7,215 men and 12,783 women) aged 40-69 years. During 11.8 years of follow-up, 101 subjects (69 men and 32 women) were newly diagnosed with HCC. Case patients were grouped according to consumption of isoflavones and soy products and stratified by hepatitis virus infection. Hazard ratios (HRs) and 95% confidence intervals (CIs) for HCC were calculated by Cox proportional-hazards modeling. In women, genistein and daidzein were dose-dependently associated with an increased risk of HCC, with multivariable HRs for the highest versus lowest tertile of 3.19 (95%CI = 1.13-9.00, p(trend) = 0.03) and 3.90 (95% CI = 1.30-11.69, p(trend) = 0.01), respectively. No association between isoflavones and HCC was observed in men. These results persisted when analysis was restricted to subjects positive for either or both hepatitis C and B virus. In conclusion, isoflavone consumption may be associated with an increased risk of HCC in women. Women with hepatitis virus infection may be advised to abstain from isoflavone consumption. Further studies are warranted to confirm these findings.

Investigating the Optimal Soy Protein and Isoflavone Intakes for Women: A Perspective

Traditional soyfoods have been consumed for centuries throughout much of East Asia and, recently, these foods have also become popular in the West. Soyfoods and specific soybean components, such as the protein and isoflavones, have attracted attention for their possible health benefits. Isoflavones are classified as phytoestrogens and have been postulated to be natural alternatives to hormone therapy for menopausal women. To provide guidance on optimal soy intake, this article evaluates Asian soy consumption and both clinical and Asian epidemiologic studies that examined the relationship between soy intake and a variety of health outcomes. On the basis of these data and the standard principles of dietary practice the author suggests that optimal soy protein and isoflavone intakes are 15–20 g/day and 50–90 mg/day, respectively. In addition, an intake of 25 g/day soy protein can be specifically used as the recommendation for cholesterol reduction.

Bone mass and soy isoflavones in socially housed, premenopausal macaques

BACKGROUND

Soy consumption is associated with a lower incidence of hip fracture in Asian than in Western women, an effect often attributed to estrogen-like compounds (isoflavones) in soy. It is not known whether premenopausal soy exposure initiated in adulthood can increase bone mass and thereby reduce fracture risk.

OBJECTIVE

We aimed to determine whether a high-isoflavone soy diet influences bone mass in soy-naïve, premenopausal cynomolgus monkeys (Macaca fascicularis).

DESIGN

Ninety-four skeletally mature females were randomly assigned to consume diets whose protein content came from either high-isoflavone soy or casein and lactalbumin. Animals were socially housed. Bone mass and circulating isoflavone concentrations were measured at baseline and 19 and 31 mo after the start of treatment; bone biomarkers were measured at baseline and 31 mo.

RESULTS

There were no significant differences at any timepoint in whole-body bone mineral content between casein-fed (112.5 +/- 2.1, 119.2 +/- 1.9, and 120.7 +/- 2.1 g) and soy-fed (117.2 +/- 2.1, 122.4 +/- 2.0, and 125.4 +/- 2.3 g; P=0.12) monkeys. Similar results were seen for spinal bone mineral density (casein-fed: 0.46 +/- 0.01, 0.50 +/- 0.01, and 0.52 +/- 0.01 g/cm(2); soy-fed: 0.47 +/- 0.01, 0.51 +/- 0.01, and 0.52 +/- 0.01 g/cm(2); P=0.30) and bone biomarker measurements-bone-specific alkaline phosphatase (soy-fed: 82.3 +/- 4.1 and 63.2 +/- 3.4 ng/mL; casein-fed: 94.1 +/- 4.5 and 61.7 +/- 4.3 ng/mL; P=0.22) and C-terminal crosslink of type 1 collagen (soy-fed: 0.944 +/- 0.06 and 0.89 +/- 0.08 nmol/L; casein-fed: 0.97 +/- 0.07 and 0.78 +/- 0.06 nmol/L; P=0.20).

CONCLUSION

A soy diet high in isoflavones does not significantly affect bone characteristics in initially soy-naïve premenopausal monkeys.

Associations among maternal soy intake, isoflavone levels in urine and blood samples, and maternal and umbilical hormone concentrations (Japan)

OBJECTIVES

In utero exposure to high levels of endogenous estrogens has been hypothesized to increase breast cancer risk in later life. A high intake of soy has been suggested to protect against breast cancer. We examined the hypothesis that maternal soy intake may be inversely associated with pregnancy hormone levels.

METHODS

The concentrations of hormones (estradiol, estriol, and testosterone) and isoflavones (genistein, deidzein, and equol) were measured in the maternal urine and serum, and umbilical cord blood of 194 women during pregnancy and at delivery. Soy intake during pregnancy was assessed by 5-day diet records at approximately the 29th week of pregnancy.

RESULTS

High correlations were observed for isoflavone levels between maternal samples and umbilical cord blood, indicating that isoflavone can be transferred from the maternal to the fetal compartment. None of the hormones measured in umbilical cord blood was significantly associated with any of the isoflavones measured. There were a few significant associations between maternal hormone levels and isoflavone measures during pregnancy, but their patterns of associations varied by gestational week and differed depending on whether isoflavone exposure was measured by diet records, urine or serum.

CONCLUSION

Our data contain no strong evidence showing that soy intake affects hormone levels during pregnancy.

Estimated Asian adult soy protein and isoflavone intakes

There is substantial interest in the possible anticancer effects of soy foods. In part, this is because of the historically low incidence rates of breast and prostate cancer in Asia. Of the several putative soybean chemopreventive agents, isoflavones have received the most attention. Awareness of this research has led increasing numbers of consumers to use soy foods, isoflavone-fortified foods, and isoflavone supplements. Therefore, there is a need for guidance regarding appropriate isoflavone intake levels. To this end, this article analyzed soy protein (as a surrogate for isoflavones) and isoflavone intake of the major soy food-consuming countries using individual dietary surveys for the bulk of the information. In total, 24 surveys from 4 countries that met the inclusion criteria were identified: Japan (n = 11), China (n = 7), Hong Kong (n = 4), and Singapore (n = 2). The results indicate that older Japanese adults consume approximately 6-11 g of soy protein and 25-50 mg of isoflavones (expressed as aglycone equivalents) per day. Intake in Hong Kong and Singapore is lower than in Japan, whereas significant regional intake differences exist for China. Evidence suggests that < or =10% of the Asian population consumes as much as 25 g of soy protein or 100 mg of isoflavones per day. The applicability of these findings for making soy intake recommendations for non-Asians is discussed.

Neonatal exposure to the phytoestrogen genistein alters mammary gland growth and developmental programming of hormone receptor levels

Developmental effects of genistein (Gen) on the mammary gland were investigated using outbred female CD-1 mice treated neonatally on d 1-5 by sc injections at doses of 0.5, 5, or 50 mg/kg.d. Examination of mammary gland whole mounts (no. 4) before puberty (4 wk) revealed no morphological differences in development after Gen treatment. However, mice treated with Gen-50 had stunted development characterized by less branching at 5 wk and decreased numbers of terminal end buds at 5 and 6 wk. Conversely, at 6 wk, Gen-0.5-treated mice exhibited advanced development with increased ductal elongation compared with controls. Measurements of hormone receptor levels showed increased levels of progesterone receptor protein and estrogen receptor-beta mRNA in Gen-0.5-treated mice compared with controls; ERalpha expression was decreased after all doses of Gen treatment. Lactation ability, measured by pup weight gain and survival, was not affected after neonatal Gen-0.5 and Gen-5. Mice treated with Gen-50 did not deliver live pups; therefore, lactation ability could not be determined. Evaluation of mammary glands in aged mice (9 months) showed no differences between Gen-0.5-treated mice and controls but mice treated with Gen-5 and Gen-50 exhibited altered morphology including reduced lobular alveolar development, dilated ducts, and focal areas of "beaded" ducts lined with hyperplastic ductal epithelium. In summary, neonatal Gen exposure altered mammary gland growth and development as well as hormone receptor levels at all doses examined; higher doses of Gen led to permanent long-lasting morphological changes.

Addressing the soy and breast cancer relationship: review, commentary, and workshop proceedings

The impact of soyfood intake on breast cancer risk has been investigated extensively. Much of this focus can be attributed to the soybean being a dietary source that is uniquely rich in isoflavones. The chemical structure of isoflavones is similar to that of estrogen, and isoflavones bind to both estrogen receptors (ER alpha and ER beta) (although they preferentially bind to and activate ER beta) and exert estrogen-like effects under some experimental conditions. Isoflavones also possess nonhormonal properties that are associated with the inhibition of cancer cell growth. Thus, there are several possible mechanisms by which soy may reduce the risk of breast cancer. However, the role of isoflavones in breast cancer has become controversial because, in contrast to the possible beneficial effects, some data from in vitro and animal studies suggest that isoflavones, especially genistein, the aglycone of the main soybean isoflavone genistin, may stimulate the growth of estrogen-sensitive tumors. Limited human data directly address the tumor-promoting effects of isoflavones and soy. Because the use of soyfoods and isoflavone supplements is increasing, it is important from a public health perspective to understand the impact of these products on breast cancer risk in women at high risk of the disease and on the survival of breast cancer patients. To this end, a workshop was held in November 2005 to review the existing literature and to make research recommendations. This paper summarizes the workshop findings and recommendations. The primary research recommendation is that the impact of isoflavones on breast tissue needs to be evaluated at the cellular level in women at high risk for breast cancer.

Short-term soy and probiotic supplementation does not markedly affect concentrations of reproductive hormones in postmenopausal women with and without histories of breast cancer

BACKGROUND

Observational studies suggest that dietary isoflavones reduce breast cancer risk, and this may be caused in part by effects on endogenous hormone concentrations. Because intestinal bacteria metabolize isoflavones, it was hypothesized that consumption of probiotic bacteria would enhance the biologic effects of isoflavones, including effects on endogenous hormones.

DESIGN

Twenty (20) postmenopausal breast cancer survivors and 20 healthy postmenopausal women completed four 42-day diet periods in a randomized, crossover design. They received one of the following: isolated soy protein; isolated milk protein; soy + probiotic capsules; or milk + probiotic capsules. Each protein supplement provided 0.38 g protein/(kg body weight/day) (26.6 +/- 4.5 g protein/day) and soy protein provided 0.64 mg isoflavones/(kg body weight/day) (44.4 +/- 7.5 mg isoflavones/day). Probiotic capsules provided 10(9) colony-forming units Lactobacillus acidophilus (strain DDS-1), Bifidobacterium longum, and 15-20 mg fructo-oligosaccharide.

MEASURES

Plasma samples were collected at baseline and after each diet for analysis of estrogens, follicle-stimulating hormone (FSH), androgens, and sex hormone?binding globulin (SHBG).

RESULTS

Hormone levels were not affected by soy, probiotic supplements, or equol producer status, and neither cancer status nor equol producer status altered the effects of soy or probiotics. Furthermore probiotics did not alter the effects of soy consumption. Soy protein tended to decrease SHBG compared to milk protein diets (p = 0.05), although both proteins significantly decreased SHBG relative to baseline (p = 0.0001 and p = 0.03).

CONCLUSIONS

These data suggest that short-term, moderate consumption of isoflavone-containing soy protein and consumption of these particular probiotic capsules do not significantly alter reproductive hormone concentrations in breast cancer survivors or controls, regardless of equol producer status.

Effects of soy on the mammary glands of premenopausal female monkeys

OBJECTIVE

To evaluate the interactive effects of dietary soy and menstrual cycle phase on breast proliferation, apoptosis, and sex steroid receptor expression in premenopausal female cynomolgus monkeys.

DESIGN

Animals were randomized to receive diets with either casein lactalbumin or soy as the protein source for 12 months. Paired follicular and luteal mammary gland biopsies were taken before and after treatment and evaluated for epithelial proliferation and area, apoptosis, and sex steroid receptor expression.

SETTING

Academic research environment.

ANIMAL(S)

Fifty-two adult female cynomolgus monkeys (Macaca fascicularis).

INTERVENTION(S)

Soy protein with the human equivalent of 129 mg/d of isoflavones.

MAIN OUTCOME MEASURE(S)

Breast proliferation and epithelial area.

RESULT(S)

Follicular and luteal assessments were taken on cycle day (+/- SE) 5.3 +/- 0.1 and 22.0 +/- 0.1, respectively. Serum E2, serum P, breast proliferation, and vaginal maturation were significantly higher in the luteal vs. follicular phase. Soy treatment resulted in significantly higher serum isoflavone concentrations compared with the casein lactalbumin group but did not significantly affect breast proliferation, epithelial area, apoptosis, or progesterone receptor expression; uterine size; or vaginal maturation in either the follicular or luteal phase.

CONCLUSION(S)

Results indicate that dietary levels of soy intake have no detectable hormonal effects on the premenopausal breast.

Tea, hormone-related cancers and endogenous hormone levels

Tea is one of the most popular beverages consumed around the world, second only to water. There has been substantial interest in the potential role of tea in cancer prevention, particularly in respiratory and gastrointestinal tract cancers. Recent epidemiological data have linked tea intake to reduced risk of hormone-related cancers, including breast, ovarian and prostate cancers. Based on sparse data, there is suggestion that tea intake may influence circulating hormone levels, providing a plausible mechanism whereby tea intake may influence risk of hormone-related cancers. The major objectives of this paper are to review the epidemiological evidence on tea and risk of breast, ovarian, and prostate cancers as well as the human and non-human studies on tea and circulating hormone levels. We pay special attention to some of the limitations of the human studies and discuss future research needs.

Meta-Analysis of Soy Intake and Breast Cancer Risk

BACKGROUND

High intake of soy foods has been proposed to contribute to the low breast cancer risk in Asian countries. However, results of epidemiologic studies of this association are highly variable, and experimental data suggest that soy constituents can be estrogenic and potentially risk enhancing. Thus, rigorous evaluation of available epidemiologic data is necessary before appropriate recommendations can be made, especially for women at high risk of breast cancer or those who have survived the disease.

METHODS

We performed a meta-analysis of 18 epidemiologic studies (12 case-control and six cohort or nested case-control) published from 1978 through 2004 that examined soy exposure and breast cancer risk. Pooled relative risk estimates were based on either the original soy exposure measure defined in each study or on an estimate of daily soy protein intake.

RESULTS

Risk estimates, levels and measures of soy exposure, and control for confounding factors varied considerably across studies. In a pooled analysis, among all women, high soy intake was modestly associated with reduced breast cancer risk (odds ratio [OR] = 0.86, 95% confidence interval [CI] = 0.75 to 0.99); the association was not statistically significant among women in Asian countries (OR = 0.89, 95% CI = 0.71 to 1.12). Among the 10 studies that stratified by menopausal status the inverse association between soy exposure and breast cancer risk was somewhat stronger in premenopausal women (OR = 0.70, 95% CI = 0.58 to 0.85) than in postmenopausal women (OR = 0.77, 95% CI = 0.60 to 0.98); however, eight studies did not provide menopause-specific results, six of which did not support an association. When exposure was analyzed by soy protein intake in grams per day, a statistically significant association with breast cancer risk was seen only among premenopausal women (OR = 0.94, 95% CI = 0.92 to 0.97).

CONCLUSIONS

Soy intake may be associated with a small reduction in breast cancer risk. However, this result should be interpreted with caution due to potential exposure misclassification, confounding, and lack of a dose response. Given these caveats and results of some experimental studies that suggest adverse effects from soy constituents, recommendations for high-dose isoflavone supplementation to prevent breast cancer or prevent its recurrence are premature.

Soybean products and reduction of breast cancer risk: a case-control study in Japan

Components of the Japanese diet, which might contribute to the relatively low breast cancer incidence rates in Japan, have not been clarified in detail. Since soybean products are widely consumed in Japan, a case-control study taking account of the menopausal status was conducted using data from the hospital-based epidemiologic research program at Aichi Cancer Center (HERPACC). In total, 167 breast cancer cases were included and 854 women confirmed as free of cancer were recruited as the control group. Odds ratios (OR) and 95% confidence intervals (95% CI) were determined by multiple logistic regression analysis. There were reductions in risk of breast cancer associated with high intake of soybean products among premenopausal women. Compared with women in the lowest tertile, the adjusted ORs for top tertile intake of tofu (soybean curd) was 0.49 (95% CI, 0.25-0.95). A significant decrease in premenopausal breast cancer risk was also observed for increasing consumption of isoflavones (OR=0.44; 95% CI, 0.22-0.89 for highest vs lowest tertile; P for trend=0.02). The present study found a statistically inverse association between tofu or isoflavone intake and risk of breast cancer in Japanese premenopausal women, while no statistically significant association was evident with the risk among postmenopausal women.

Low-Dose Dietary Phytoestrogen Abrogates Tamoxifen-Associated Mammary Tumor Prevention

Wild-type erbB-2/neu transgenic mice were used to study the interactions between tamoxifen and dietary phytoestrogens (or isoflavones) by dose and form in vivo. Mice were randomized to one of four dietary formulas and implanted with an 8-week continuous-release tamoxifen or placebo pellet at 8 weeks of age. In placebo-treated mice, soy meal diet (but not diets supplemented with low-dose or high-dose isoflavones or a casein diet) resulted in prolongation of tumor latency. In tamoxifen-treated mice fed the soy meal, casein, or high-dose isoflavone enriched diets, the majority (&gt;80%) showed no tumor formation by 60 weeks of age. Of the mice that developed tumors, latency was significantly prolonged. In tamoxifen-treated mice fed the low-dose isoflavone enriched diet, a much higher rate of mammary tumor development (&gt;50%; P &lt; 0.002) and a shorter tumor latency were observed. In vitro studies of human and mouse mammary tumor cell lines confirm that low doses of genistein, co-administered with tamoxifen, promote cell proliferation. This is in contrast to tamoxifen alone or tamoxifen with higher doses of genistein that are growth inhibitory. In summary, low-dose dietary isoflavones abrogated tamoxifen-associated mammary tumor prevention in vivo. These interactions are supported by in vitro data from human and mouse mammary tumor cell lines. These dose-associated interactions likely have relevance to the human use of tamoxifen for prevention or treatment of breast cancer.

Hormonal Response to Diets High in Soy or Animal Protein Without and With Isoflavones in Moderately Hypercholesterolemic Subjects

Consumption of soy protein has been associated with altered risk of developing endocrine-regulated cancers. This study was designed to assess the independent effect of soy relative to animal protein and soy-derived isoflavones on circulating estrogen and androgen concentrations in postmenopausal women and older men. Forty-two subjects (> 50 yr) with low-density lipoprotein cholesterol levels of > or = 3.36 mmol/l were fed each of 4 diets in randomized order for 6 wk/phase. All food and drink were provided. Diets contained 25 g soy or common sources of animal protein/4.2 MJ containing trace or 50 mg isoflavones/4.2 MJ. At the end of each diet phase, concentrations of estrone sulfate, estrone, estradiol, testosterone, androstendione, dihydrotestosterone, dehydroepiandrosterone, and dehydroepiandrosterone sulfate were measured. In postmenopausal women, concentrations of estrone were higher and its precursor, dehydroepiandrosterone, lower after consuming the soy compared with animal protein diets (P = 0.0396 and 0.0374, respectively). There was no significant effect of isoflavones on any of the hormones measured. In older men, dehydroepiandrosterone sulfate concentrations were lower after consuming the isoflavone (P = 0.0106) and higher after soy, compared with the animal protein diets (P = 0.0118). These data suggest that relatively large amounts of soy protein or soy-derived isoflavones had modest and limited sex-specific effects on circulating hormone levels.

Phytoestrogens: end of a tale?

Phytoestrogens are plant-derived hormone-like diphenolic compounds of dietary origin that are present at high levels in plasma of subjects living in areas with low atherosclerosis and cancer incidence. The term phytoestrogen is commonly applied to the soy isoflavones genistein, daidzein and glycitein. As outlined in a previous review article in this journal by Adlercreutz and Mazur 1, these compounds are weakly estrogenic and appear to influence the cardiovascular system, the production, metabolism and biological activity of sex-hormones, as well as malignant cell proliferation, differentiation and angiogenesis. Recently skepticism has developed concerning the true potential of phytoestrogens to beneficially modify these processes. A critical analysis of the early findings from supplementing the diet with soy protein has failed to confirm phytoestrogens as the responsible agent for beneficial cardiovascular effects, be it by way of lipid reduction, vasodilation or lipoprotein oxidation. Furthermore, contrasting data have been reported on the potential of phytoestrogens to prevent hormone-dependent cancers (e.g. breast and prostate) and to successfully treat post-menopausal complaints, an indication for which they are widely used. These potentially negative findings have led health authorities in several countries to suggest maximum daily intake levels for phytoestrogens. There is now growing interest in the use of soy products containing low levels of phytoestrogens and in research on other phytoestrogen free legumes such as lupin.

Computational modeling of serum-binding proteins and clearance in extrapolations across life stages and species for endocrine active compounds

One measure of the potency of compounds that lead to the effects through ligand-dependent gene transcription is the relative affinity for the critical receptor. Endocrine active compounds that are presumed to act principally through binding to the estrogen receptor (e.g., estradiol, genistein, bisphenol A, and octylphenol) comprise one class of such compounds. For making simple comparisons, receptor-binding affinity has been equated to in vivo potency, which consequently defines the dose-response characteristics for the compound. Direct extrapolation of in vitro estimated affinities to the corresponding in vivo system and to specific species or life stages (e.g., neonatal, pregnancy) can be misleading. Accurate comparison of the potency of endocrine active compounds requires characterization of biochemical and pharmacokinetic factors that affect their free concentration. Quantitative in vitro and in vivo models were developed for integrating pharmacokinetics factors (e.g., serum protein and receptor-binding affinities, clearance) that affect potency. Data for parameterizing these models for several estrogenic compounds were evaluated and the models exercised. While simulations of adult human or rat sera were generally successful, difficulties in describing early life stages were identified. Exogenous compounds were predicted to be largely ineffective at competing estradiol off serum-binding proteins, suggesting this was unlikely to be physiologically significant. Discrepancies were identified between relative potencies based upon modeling in vitro receptor-binding activity versus in vivo activity in the presence of clearance and serum-binding proteins. The examples illustrate the utility of this approach for integrating available experimental data from in vitro and in vivo studies to estimate the relative potency of these compounds.

Evaluation and management of breast pain

Pain is one of the most common breast symptoms experienced by women. It can be severe enough to interfere with usual daily activities, but the etiology and optimal treatment remain undefined. Breast pain is typically approached according to its classification as cyclic mastalgia, noncyclic mastalgia, and extramammary (nonbreast) pain. Cyclic mastalgia is breast pain that has a clear relationship to the menstrual cycle. Noncyclic mastalgia may be constant or intermittent but is not associated with the menstrual cycle and often occurs after menopause. Extramammary pain arises from the chest wall or other sources and is interpreted as having a cause within the breast. The risk of cancer in a woman presenting with breast pain as her only symptom is extremely low. After appropriate clinical evaluation, most patients with breast pain respond favorably to a combination of reassurance and nonpharmacological measures. The medications danazol, tamoxifen, and bromocriptine are effective; however, the potentially serious adverse effects of these medications limit their use to selected patients with severe, sustained breast pain. The status of other therapeutic strategies and directions for future research are discussed.

Phytoestrogens, cancer and coronary heart disease

Recent results obtained in collaboration with many other groups with regard to phytoestrogens (isoflavones and lignans) and breast cancer, prostate cancer and cardiovascular disease are presented and discussed in light of new developments in the field. Both isoflavones and lignans may be protective with regard to these diseases, but we do not yet understand some of the controversial results obtained. In this short communication the possible mechanisms of disease prevention were not discussed.

Effects of dietary soy and estrous cycle on adrenal cytochrome P450 1B1 expression and DMBA metabolism in adrenal glands and livers in female Sprague–Dawley rats

Cytochrome p450 1B1 (CYP1B1) has been shown to be important in the bioactivation of 7,12-dimethylbenz[a]anthracene (DMBA) to an adrenal toxin in rats. We investigated the effects of diet and stage of estrous cycle on CYP1B1 expression in rat adrenal glands and on DMBA metabolism by rat adrenal and hepatic microsomes. Female Sprague-Dawley (SD) rats were placed on either standard soy-containing NIH-31 rat chow or soy- and alfalfa-free 5K96 diet from postnatal day (PND) 21 until sacrifice at PND50+/-5. Stage of estrous at sacrifice was assessed by vaginal cytology and confirmed by histological examination of the vagina. Dietary soy at the level present in NIH-31 diet did not affect serum estrogen and progesterone levels. Immunohistochemical analysis confirmed that CYP1B1 was exclusively expressed in the zona fasciculata and zona reticularis in adrenal cortex, which are the regions vulnerable to DMBA-induced adrenal necrosis. Adrenal CYP1B1 protein expression, 3H-DMBA depletion, and formation of DMBA-3,4-, and -8,9-dihydrodiols by adrenal microsomes were greater in animals fed 5K96 diet, and the stage of the estrous cycle affected these parameters only in the soy-free 5K96 diet. In hepatic microsomes, the formation of DMBA-3,4-dihydrodiol, 7-hydroxy- and 12-hydroxy-DMBA were lower in animals fed NIH-31 diet than in those fed 5K96 diet. Thus, dietary soy and the estrous cycle appear to regulate adrenal CYP1B1 expression and DMBA metabolism by both adrenal and hepatic microsomes. The use of different basal diets containing variable levels of soy components may affect certain toxicity assessments.

Dietary factors protective against breast cancer in Japanese premenopausal and postmenopausal women

Since components of the Japanese diet that might be responsible for the relatively low breast cancer incidence rates observed in Japan have not been clarified in detail, a case-referent study with reference to menopausal status was conducted using data from the hospital-based epidemiologic research program at Aichi Cancer Center (HERPACC). In total, 2,385 breast cancer cases were included, and 19,013 women, confirmed as free of cancer, were recruited as the reference group. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were determined by multiple logistic regression analysis. There were reductions in risk associated with high intake of milk and green-yellow vegetables (green leafy vegetables, carrots and pumpkins) among both pre- and postmenopausal women. The protective effects of the Japanese diet were more prominent among postmenopausal than premenopausal women. The adjusted OR of fish consumption (5 or more times per week vs. fewer than 3 times per month) was 0.75 (95% CI 0.57-0.98, p(trend) = 0.01) for postmenopausal breast cancer. A significant decrease in postmenopausal breast cancer risk was also observed for increasing intake of fruit (OR = 0.61, 95% CI 0.41-0.91). Thus, traditional Japanese dietary factors may protect against breast cancer development, especially among postmenopausal women.

Is Naturopathy as Effective as Conventional Therapy for Treatment of Menopausal Symptoms?

BACKGROUND

Although the use of alternative medicine in the United States is increasing, no published studies have documented the effectiveness of naturopathy for treatment of menopausal symptoms compared to women receiving conventional therapy in the clinical setting.

OBJECTIVE

To compare naturopathic therapy with conventional medical therapy for treatment of selected menopausal symptoms.

DESIGN

A retrospective cohort study, using abstracted data from medical charts.

SETTING

One natural medicine and six conventional medical clinics at Community Health Centers of King County, Washington, from November 1, 1996, through July 31, 1998.

PATIENTS

Women aged 40 years of age or more with a diagnosis of menopausal symptoms documented by a naturopathic or conventional physician.

MAIN OUTCOME MEASURES

Improvement in selected menopausal symptoms.

RESULTS

In univariate analyses, patients treated with naturopathy for menopausal symptoms reported higher monthly incomes ($1848.00 versus $853.60), were less likely to be smokers (11.4% versus 41.9%), exercised more frequently, and reported higher frequencies of decreased energy (41.8% versus 24.4%), insomnia (57.0% versus 33.1%), and hot flashes (69.6% versus 55.6%) at baseline than those who received conventional treatment. In multivariate analyses, patients treated with naturopathy were approximately seven times more likely than conventionally treated patients to report improvement for insomnia (odds ratio [OR], 6.77; 95% confidence interval [CI], 1.71, 26.63) and decreased energy (OR, 6.55; 95% CI, 0.96, 44.74). Naturopathy patients reported improvement for anxiety (OR, 1.27; 95% CI, 0.63, 2.56), hot flashes (OR, 1.40; 95% CI, 0.68, 2.88), menstrual changes (OR, 0.98; 95% CI, 0.43, 2.24), and vaginal dryness (OR, 0.91; 95% CI, 0.21, 3.96) about as frequently as patients who were treated conventionally.

CONCLUSIONS

Naturopathy appears to be an effective alternative for relief of specific menopausal symptoms compared to conventional therapy.

Isoflavone intake in four different European countries: the VENUS approach

The aim of this study was to identify the level of isoflavone intake (total isoflavones, daidzein and genistein) in four European countries: Ireland, Italy, The Netherlands and the UK. For this purpose national food composition databases of isoflavone content were created in a comparable way, using the Vegetal Estrogens in Nutrition and the Skeleton (VENUS) analytical database as a common basis, and appropriate food consumption data were selected. The isoflavone intake in Ireland, Italy, The Netherlands and the UK is on average less than 1 mg/d. Small groups of consumers of soya foods could be identified in Ireland, The Netherlands and the UK. The estimated intake levels are low compared with those found in typical Asian diets (approximately 20-100 mg/d) and also low compared with levels where physiological effects are expected (60-100 mg/d). The results (including a subgroup analysis of soya product consumers) showed that such levels are difficult to achieve with the European diets studied here.

Effects of supplementation with purified red clover (Trifolium pratense) isoflavones on plasma lipids and insulin resistance in healthy premenopausal women

Consumption of isoflavone-rich soyabean protein is reported to reduce total and LDL-cholesterol, but the specific components responsible are undetermined. In a previous crossover trial we showed that purified isoflavones, derived from red clover (Trifolium pratense), raised HDL3-cholesterol in premenopausal women; however, these findings were inconclusive due to period and carryover effects. In an attempt to overcome this problem, we utilised a parallel study designed to re-examine the effects of purified isoflavones on plasma lipoproteins and markers of insulin resistance in premenopausal women. Twenty-five healthy premenopausal women participated in a double-blind, randomised, parallel study. The treatment group (n 12) consumed a placebo for the first menstrual cycle and an isoflavone supplement (86 mg/d, derived from red clover) for three cycles, while the placebo group (n 13) consumed a placebo supplement for four menstrual cycles. Blood samples were collected weekly during cycles 1, 3 and 4. Supplementation with isoflavones resulted in a 15-fold increase in urinary isoflavone excretion (P<0.0001). There were no significant effects on total cholesterol, LDL- and HDL-cholesterol, HDL subfractions, triacylglycerol, lipoprotein(a), glucose or insulin concentrations. Our present results indicate that purified isoflavones derived from red clover have no effect on cholesterol homeostasis or insulin resistance in premenopausal women, a group which is at low risk of CHD.

The role of nutrition in preventing prostate cancer: a review of the proposed mechanism of action of various dietary substances

BACKGROUND

Dietary modifications to prevent prostate cancer (PCa) continue to gain attention as research demonstrates that various dietary nutrients/supplements are related to decreased risk of developing prostate cancer (PCa). Several studies have focused on the antioxidant and nonantioxidant effects of various dietary substances in the prevention of PCa. Research into the mechanisms by which PCa is prevented, or its disease severity is reduced by dietary micronutrients and vitamins continues to enrich our understanding of the mechanisms by which PCa is initiated and progresses.

METHODS

We reviewed the literature on dietary nutrients with antioxidant properties that have been shown to have a positive effect in reducing the incidence or preventing the occurrence of PCa including carotenoids (e.g., lycopene), retinoids (e.g., vitamin A), vitamin E, vitamin C, selenium, and polyphenols. Other nutrients examined included vitamin D and calcium.

RESULTS

Many dietary micronutrients have demonstrated significant and complex effects on PCa cell proliferation, differentiation, and signaling related to the initiation, progression, and regression of PCa.

CONCLUSION

Understanding the mechanisms by which various dietary nutrients exert their effects on PCa may make it possible to design effective drugs for treating PCa and to promote better nutrition and lifestyle changes in those at risk for PCa.

Soy product intake is inversely associated with serum homocysteine level in premenopausal Japanese women

Soybeans, which are an excellent source of folate, vitamin B-6 and minerals, may reduce serum homocysteine level. However, there is a possibility that dietary soy raises the serum homocysteine level because isoflavones, which are weak estrogens contained in soybeans, may exert antiestrogenic effects in a high estrogen environment, such as in premenopausal women. The present study examined a cross-sectional relationship between soy product intake and serum homocysteine level in 201 premenopausal Japanese women. Intakes of soy products, folate, methionine and vitamins B-6 and B-12 were estimated by a semiquantitative food frequency questionnaire. Folate status was also assessed by measuring serum folate. Soy product intake in terms of soy protein as well as soy isoflavone intake was modestly but significantly inversely associated with serum homocysteine level (r = -0.15, P = 0.04) after controlling for covariates. Soy product intake was also significantly positively correlated with serum folate (r = 0.15, P = 0.04). Although it is unclear the extent to which each component of soy, such as folate and isoflavones, is associated with the serum homocysteine concentration, this biochemical complex appears to have a favorable effect on homocysteine metabolism in premenopausal women.