Effects of replacing meat with soyabean in the diet on sex hormone concentrations in healthy adult males

α-Tocotrienol in rice bran enhances steroidogenesis in mouse Leydig cell via increased gene expression of steroidogenic acute regulatory protein and induction of its mitochondrial translocation

Rice is a staple food in the Asian region and one of the world's major energy sources. Testosterone is a steroid hormone that maintains physical, sexual, and cognitive ability, and its decline causes health problems like late-onset hypogonadism. Evaluation of various grain extracts showed rice bran to stimulate testosterone secretion from Leydig model cells. α-Tocotrienol was found as a bioactive compound in rice bran, and mechanistic analysis showed the stimulation of steroid hormone synthesis through enhanced gene expression of steroidogenic acute regulatory protein as well as inducing mitochondrial localization of the protein. Preliminary study showed an increasing trend in serum testosterone levels in mice by oral intake of α-tocotrienol. These results suggest that α-tocotrienol intake may be effective in preventing symptoms caused by low testosterone levels.

Estrogenic Pastures: A Source of Endocrine Disruption in Sheep Reproduction

Phytoestrogens can impact on reproductive health due to their structural similarity to estradiol. Initially identified in sheep consuming estrogenic pasture, phytoestrogens are known to influence reproductive capacity in numerous species. Estrogenic pastures continue to persist in sheep production systems, yet there has been little headway in our understanding of the underlying mechanisms that link phytoestrogens with compromised reproduction in sheep. Here we review the known and postulated actions of phytoestrogens on reproduction, with particular focus on competitive binding with nuclear and non-nuclear estrogen receptors, modifications to the epigenome, and the downstream impacts on normal physiological function. The review examines the evidence that phytoestrogens cause reproductive dysfunction in both the sexes, and that outcomes depend on the developmental period when an individual is exposed to phytoestrogen.

Neither soy nor isoflavone intake affects male reproductive hormones: An expanded and updated meta-analysis of clinical studies

Concerns that the phytoestrogens (isoflavones) in soy may feminize men continue to be raised. Several studies and case-reports describing feminizing effects including lowering testosterone levels and raising estrogen levels in men have been published. For this reason, the clinical data were meta-analyzed to determine whether soy or isoflavone intake affects total testosterone (TT), free testosterone (FT), estradiol (E₂), estrone (E₁), and sex hormone binding globulin (SHBG). PubMed and CAB Abstracts databases were searched between 2010 and April 2020, with use of controlled vocabulary specific to the databases. Peer-reviewed studies published in English were selected if (1) adult men consumed soyfoods, soy protein, or isoflavone extracts (from soy or red clover) and [2] circulating TT, FT, SHBG, E2 or E1 was assessed. Data were extracted by two independent reviewers. With one exception, studies included in a 2010 meta-analysis were included in the current analysis. A total of 41 studies were included in the analyses. TT and FT levels were measured in 1753 and 752 men, respectively; E₂ and E₁ levels were measured in 1000 and 239 men, respectively and SHBG was measured in 967 men. Regardless of the statistical model, no significant effects of soy protein or isoflavone intake on any of the outcomes measured were found. Sub-analysis of the data according to isoflavone dose and study duration also showed no effect. This updated and expanded meta-analysis indicates that regardless of dose and study duration, neither soy protein nor isoflavone exposure affects TT, FT, E₂ or E₁ levels in men.

Sex-specific associations of habitual intake of soy protein and isoflavones with risk of type 2 diabetes

BACKGROUND & AIMS

A possible mechanism by which intake of soy isoflavones leads to an improvement in glucose metabolism has been suggested. However, epidemiological evidence of a link between dietary soy isoflavone and type 2 diabetes is not convincing. This study aimed to evaluate the prospective associations between intake of dietary soy protein and isoflavones (total isoflavones, daidzein and genistein) and risk of type 2 diabetes in a community-based cohort of Korean adults aged ≥ 40 years, the Korean Multi-Rural Communities Cohort (MRCohort).

METHODS

A total of 8269 participants who did not have type 2 diabetes were enrolled. Dietary intake was calculated using a food frequency questionnaire.

RESULTS

Over 50,063 person-years of follow-up, 531 participants developed type 2 diabetes. Significant dose-response inverse associations were observed between dietary soy protein and isoflavones (quartiles) and type 2 diabetes in women (incidence rate ratio, IRR = 0.63, 95% CI = 0.45-0.87, P for trend = 0.0078 for soy protein; IRR = 0.62, 95% CI = 0.45-0.86, P for trend = 0.0031 for total isoflavones for the highest quartile compared with the lowest quartile). Similar significant linear trends were found for both daidzein and genistein. However, there were no significant associations with soy protein and isoflavones in men. The sex-specific differences in associations between soy protein and isoflavones intakes and type 2 diabetes risk were statistically significant (all P for interaction < 0.05).

CONCLUSIONS

Habitual intake of soy protein and isoflavones may be inversely associated with type 2 diabetes in women, but not in men. Dietary soy components may play different roles in the development of type 2 diabetes in men and women.

The Effect of Macronutrients on Reproductive Hormones in Overweight and Obese Men: A Pilot Study

Hypogonadal obese men find it difficult to lose weight. We investigated whether the modification of macronutrient intake can alter testosterone levels independently of the body mass index. Fasted overweight or obese fertile men were asked to consume meals of polyunsaturated fats (PUFA), monounsaturated fats (MUFA), refined carbohydrates (CHO, orange juice, OJ), whey and egg albumin and mixed meals of PUFA and CHO, PUFA and egg albumin, and CHO and egg albumin. Blood was collected at fasting, then hourly for 5 h and analysed to determine the levels of testosterone and other hormones. We found PUFA and MUFA or a mixed meal of PUFA and CHO significantly reduced serum testosterone production to a similar degree over a 5 h period. PUFA decreased serum testosterone levels by 3.2 nmol/L after 1 h compared to baseline (p = 0.023), with this suppression remaining significant up to 5 h postprandially (2.1 nmol/L; p = 0.012). The net overall testosterone levels were reduced by approximately 10 nmol/L × h by PUFA, MUFA and PUFA combined with CHO. CHO alone had little effect on testosterone levels, whereas egg albumin was able to increase them (7.4 cf 2.0 nmol/L × h). Therefore, for men wishing to optimize their testosterone levels, it may be wise to avoid a high fat intake, drink liquids such as water or OJ or even consider fasting. ANZCTR, Australia; ACTRN12617001034325.

Selected Psychological Aspects of Meat Consumption-A Short Review

Eating meat is deeply entrenched in Western culture. It is often associated with wealth and a highly nutritional diet; and for many people it is also an established habit that is difficult to change. The second half of the 20th century was a period of rapid growth in meat consumption, which resulted in intensified meat production. At the same time, eating meat has recently become subject to criticism for health-related, environmental or humanitarian reasons. This review aims to signal the potential consequences of a change of diet or switching to diets that are rich/poor in certain ingredients on the functioning of the hormonal and nervous system, which translates into changes in mood and behavior. This paper discusses the psychological phenomena which underlie the difficulty of changing one's food preferences and problems encountered while adding new products to the daily diet. Finally, this study summarizes the limitations of modifying eating habits that have resulted from established attitudes and habits.

Continuous soy isoflavones exposure from weaning to maturity induces downregulation of ovarian steroidogenic factor 1 gene expression and corresponding changes in DNA methylation pattern

Female Wistar rats were treated with orally administered soy isoflavones at concentrations of 0, 25, 50, or 100mg/kg body weight from weaning until sexual maturity (3 mo.), and ovarian steroidogenesis was evaluated. After soy isoflavones were administered, a significant (P<0.05) decrease (44%) in the serum estrodial levels of the high-dose (HD) group were observed. Cultured granulosa cells from the middle- (MD) and HD groups showed significantly (P<0.05) reduced (31%, 45%, respectively) in vitro estradiol secretion, and those from the HD group showed significantly (P<0.05) reduced progesterone (25%) secretion. Compared with the control group, the mRNA expression of the steroidogenic acute regulatory protein (Star), cytochromeP450 cholesterol side chain cleavage (Cyp11a1 and Cyp19a1), and hydroxysteroid dehydrogenase 3b (Hsd3b) genes also decreased. Real-time quantitative PCR and Western blotting revealed a significant (P<0.05) decrease in key transcription factor steroidogenic factor-1 (SF-1) expression in the HD group. The detection of DNA methylation using bisulfitesequencing PCR (BSP) suggested a significantly (P<0.05) increased total methylation rate in the proximal SF-1 promoter in the HD group. Further studies showed that treatment with soy isoflavones can significantly (P<0.05) increase the mRNA expression of DNA methyltransferase (DNMT) 1 and DNMT3a. This study proved that soy isoflavone administration from weaning until sexual maturity could inhibit ovarian steroidogenesis, suggesting that SF-1 might play an important role in this effect. In addition, DNA methylation might play a role in the downregulation of SF-1 gene expression induced by soy isoflavones.

Male soy food intake was not associated with in vitro fertilization outcomes among couples attending a fertility center

Male factor etiology may be a contributing factor in up to 60% of infertility cases. Dietary intake of phytoestrogens has been related to abnormal semen quality and hormone levels. However, its effect on couple fecundity is still unclear. Intake of soy products was assessed in 184 men from couples undergoing infertility treatment with in vitro fertilization. Couples were recruited between February 2007 and May 2014 and prospectively followed to document treatment outcomes including fertilization, implantation, clinical pregnancy and live birth. Multivariate generalized linear mixed models with random intercepts, binomial distribution and logit link function were used to examine this relation while accounting for repeated treatment cycles and adjusting for potential confounders. Male partner's intake of soy foods and soy isoflavones was unrelated to fertilization rates, the proportions of poor quality embryos, accelerated or slow embryo cleavage rate, and implantation, clinical pregnancy and live birth. The adjusted live birth rates per initiated cycle (95% CI) for partners of men in increasing categories of soy food intake were 0.36 (0.28-0.45), 0.42 (0.29-0.56), 0.36 (0.24-0.51), and 0.37 (0.24-0.52), respectively. Soy food intake in men was not related to clinical outcomes among couples presenting at an infertility clinic. Data on the relation between phytoestrogens and male reproductive potential remain scarce and additional research is required to clarify its role in human reproduction.

Soy food intake and treatment outcomes of women undergoing assisted reproductive technology

OBJECTIVE

To study the relation of dietary phytoestrogens intake and clinical outcomes of women undergoing infertility treatment with the use of assisted reproductive technology (ART).

DESIGN

Prospective cohort study.

SETTING

Fertility center.

PATIENT(S)

A total of 315 women who collectively underwent 520 ART cycles from 2007 to 2013.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Implantation, clinical pregnancy, and live birth rates per initiated cycle.

RESULT(S)

Soy isoflavones intake was positively related to live birth rates in ART. Compared with women who did not consume soy isoflavones, the multivariable-adjusted odds ratios of live birth (95% confidence interval) for women in increasing categories of soy isoflavones intake were 1.32 (0.76-2.27) for women consuming 0.54-2.63 mg/d, 1.87 (1.12-3.14) for women consuming 2.64-7.55 mg/d, and 1.77 (1.03-3.03) for women consuming 7.56-27.89 mg/d.

CONCLUSION(S)

Dietary soy intake was positively related to the probability of having a live birth during infertility treatment with ART.

Environmental epigenetics and phytoestrogen/phytochemical exposures

One of the most important environmental factors to promote epigenetic alterations in an individual is nutrition and exposure to plant compounds. Phytoestrogens and other phytochemicals have dramatic effects on cellular signaling events, so have the capacity to dramatically alter developmental and physiological events. Epigenetics provides one of the more critical molecular mechanisms for environmental factors such as phytoestrogens/phytochemicals to influence biology. In the event these epigenetic mechanisms become heritable through epigenetic transgenerational mechanisms the impacts on the health of future generations and areas such as evolutionary biology need to be considered. The current review focuses on available information on the environmental epigenetics of phytoestrogen/phytochemical exposures, with impacts on health, disease and evolutionary biology considered. This article is part of a Special Issue entitled 'Phytoestrogens'.

The effects of soy and whey protein supplementation on acute hormonal reponses to resistance exercise in men

OBJECTIVE

For many resistance-trained men concerns exist regarding the production of estrogen with the consumption of soy protein when training for muscle strength and size. Thus, the purpose of this investigation was to examine the effects of soy and whey protein supplementation on sex hormones following an acute bout of heavy resistance exercise in resistance trained men.

METHODS

Ten resistance-trained men (age 21.7 ± 2.8 [SD] years; height 175.0 ± 5.4 cm; weight 84.2 ± 9.1 kg) volunteered to participate in an investigation. Utilizing a within subject randomized crossover balanced placebo design, all subjects completed 3 experimental treatment conditions supplementing with whey protein isolate (WPI), soy protein isolate (SPI), and maltodextrin placebo control for 14 days with participants ingesting 20 g of their assigned supplement each morning at approximately the same time each day. Following supplementation, subjects performed an acute heavy resistance exercise test consisting of 6 sets of 10 repetitions in the squat exercise at 80% of the subject's one repetition maximum.

RESULTS

This investigation observed lower testosterone responses following supplementation with soy protein in addition to a positive blunted cortisol response with the use of whey protein at some recovery time points. Although sex hormone binding globulin (SHBG) was proposed as a possible mechanism for understanding changes in androgen content, SHBG did not differ between experimental treatments. Importantly, there were no significant differences between groups in changes in estradiol concentrations.

CONCLUSION

Our main findings demonstrate that 14 days of supplementation with soy protein does appear to partially blunt serum testosterone. In addition, whey influences the response of cortisol following an acute bout of resistance exercise by blunting its increase during recovery. Protein supplementation alters the physiological responses to a commonly used exercise modality with some differences due to the type of protein utilized.

Soy, phytoestrogens and their impact on reproductive health

There is growing interest in the potential health threats posed by endocrine-disrupting chemicals (EDCs) to the reproductive system. Soybean is the most important dietary source of isoflavones, an important class of phytoestrogen. While consumption of soy food or phytoestrogen supplements has been frequently associated with beneficial health effects, the potentially adverse effects on development, fertility, and the reproductive and endocrine systems are likely underappreciated. Here we review the available epidemiological, clinical and animal data on the effects of soy and phytoestrogens on the development and function of the male and female reproductive system, and weigh the evidence as to their detrimental impact.

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.

Clinical pharmacology of isoflavones and its relevance for potential prevention of prostate cancer

Isoflavones are phytoestrogens that have pleiotropic effects in a wide variety of cancer cell lines. Many of these biological effects involve key components of signal transduction pathways within cancer cells, including prostate cancer cells. Epidemiological studies have raised the hypothesis that isoflavones may play an important role in the prevention and modulation of prostate cancer growth. Since randomized phase III trials of isoflavones in prostate cancer prevention are currently lacking, the best evidence for this concept is presently provided by case control studies. However, in vitro data are much more convincing in regard to the activity of a number of isoflavones, and have led to the development of genistein and phenoxodiol in the clinic as potential treatments for cancer. In addition, the potential activity of isoflavones in combination with cytotoxics or radiotherapy warrants further investigation. This review focuses on the clinical pharmacology of isoflavones and its relevance to their development for use in the prevention of prostate cancer, and it evaluates some of the conflicting data in the literature.

Soybean isoflavone exposure does not have feminizing effects on men: a critical examination of the clinical evidence

OBJECTIVE

To critically evaluate the clinical evidence, and when not available, the animal data, most relevant to concerns that isoflavone exposure in the form of supplements or soy foods has feminizing effects on men.

DESIGN

Medline literature review and cross-reference of published data.

RESULT(S)

In contrast to the results of some rodent studies, findings from a recently published metaanalysis and subsequently published studies show that neither isoflavone supplements nor isoflavone-rich soy affect total or free testosterone (T) levels. Similarly, there is essentially no evidence from the nine identified clinical studies that isoflavone exposure affects circulating estrogen levels in men. Clinical evidence also indicates that isoflavones have no effect on sperm or semen parameters, although only three intervention studies were identified and none were longer than 3 months in duration. Finally, findings from animal studies suggesting that isoflavones increase the risk of erectile dysfunction are not applicable to men, because of differences in isoflavone metabolism between rodents and humans and the excessively high amount of isoflavones to which the animals were exposed.

CONCLUSION(S)

The intervention data indicate that isoflavones do not exert feminizing effects on men at intake levels equal to and even considerably higher than are typical for Asian males.

Analytical and compositional aspects of isoflavones in food and their biological effects

This paper provides an overview of analytical techniques used to determine isoflavones (IFs) in foods and biological fluids with main emphasis on sample preparation methods. Factors influencing the content of IFs in food including processing and natural variability are summarized and an insight into IF databases is given. Comparisons of dietary intake of IFs in Asian and Western populations, in special subgroups like vegetarians, vegans, and infants are made and our knowledge on their absorption, distribution, metabolism, and excretion by the human body is presented. The influences of the gut microflora, age, gender, background diet, food matrix, and the chemical nature of the IFs on the metabolism of IFs are described. Potential mechanisms by which IFs may exert their actions are reviewed, and genetic polymorphism as determinants of biological response to soy IFs is discussed. The effects of IFs on a range of health outcomes including atherosclerosis, breast, intestinal, and prostate cancers, menopausal symptoms, bone health, and cognition are reviewed on the basis of the available in vitro, in vivo animal and human data.

Soy, phyto-oestrogens and male reproductive function: a review

There is growing interest in the possible health threat posed by the effects of endocrine disruptors on reproduction. Soy and soy-derived products contain isoflavones that mimic the actions of oestrogens and may exert adverse effects on male fertility. The purpose of this review was to examine the evidence regarding the potential detrimental effects of soy and phyto-oestrogens on male reproductive function and fertility in humans and animals. Overall, there are some indications that phyto-oestrogens, alone or in combination with other endocrine disruptors, may alter reproductive hormones, spermatogenesis, sperm capacitation and fertility. However, these results must be interpreted with care, as a result of the paucity of human studies and as numerous reports did not reveal any adverse effects on male reproductive physiology. Further investigation is needed before a firm conclusion can be drawn. In the meantime, caution would suggest that perinatal phyto-oestrogen exposure, such as that found in infants feeding on soy-based formula, should be avoided.

Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: results of a meta-analysis

OBJECTIVE

To determine whether isoflavones exert estrogen-like effects in men by lowering bioavailable T through evaluation of the effects of soy protein or isoflavone intake on T, sex hormone-binding globulin (SHBG), free T, and free androgen index (FAI) in men.

DESIGN

PubMed and CAB Abstracts databases were searched through July 1, 2008, with use of controlled vocabulary specific to the databases, such as soy, isoflavones, genistein, phytoestrogens, red clover, androgen, testosterone, and SHBG. Peer-reviewed studies published in English were selected if [1] adult men consumed soy foods, isolated soy protein, or isoflavone extracts (from soy or red clover) and [2] circulating T, SHBG, free T, or calculated FAI was assessed. Data were extracted by two independent reviewers. Isoflavone exposure was abstracted directly from studies.

MAIN OUTCOME MEASURE(S)

Fifteen placebo-controlled treatment groups with baseline and ending measures were analyzed. In addition, 32 reports involving 36 treatment groups were assessed in simpler models to ascertain the results.

RESULT(S)

No significant effects of soy protein or isoflavone intake on T, SHBG, free T, or FAI were detected regardless of statistical model.

CONCLUSION(S)

The results of this meta-analysis suggest that neither soy foods nor isoflavone supplements alter measures of bioavailable T concentrations in men.

Meat consumption and cancer risk

The authors review the key studies on the association between meat intake and cancer risk, including a new prospective cohort study by Amanda Cross and colleagues published inPLoS Medicine.

Effect of protein source and resistance training on body composition and sex hormones

Background

Evidence suggests an inverse relationship between soy protein intake and serum concentrations of male sex hormones. Anecdotal evidence indicates that these alterations in serum sex hormones may attenuate changes in lean body mass following resistance training. However, little empirical data exists regarding the effects of soy and milk-based proteins on circulating androgens and exercise induced body composition changes.

Methods

For 12 weeks 20 subjects were supplemented with 50 g per day of one of four different protein sources (Soy concentrate; Soy isolate; Soy isolate and whey blend, and Whey blend only) in combination with a resistance-training program. Body composition, testosterone, estradiol and sex hormone binding globulin (SHBG) were measured at baseline and week 12.

Results

Protein supplementation resulted in a significant increase in lean body mass independent of protein source (0.5 ± 1.1 and 0.9 ± 1.4 kg, p = 0.006, p = 0.007). No significant differences were observed between groups for total and free testosterone, SHBG, percentage body fat, BMI or body weight. The Testosterone/Estradiol ratio increased across all groups (+13.4, p = 0.005) and estradiol decreased (p = 0.002). Within group analysis showed significant increases in the Testosterone/Estradiol ratio in soy isolate + whey blend group (+16.3, p = 0.030). Estradiol was significantly lower in the whey blend group (-9.1 ± 8.7 pg/ml, p = 0.033).

Conclusion

This investigation shows that 12 week supplementation with soy protein does not decrease serum testosterone or inhibit lean body mass changes in subjects engaged in a resistance exercise program.

Isoflavone-rich soy protein isolate suppresses androgen receptor expression without altering estrogen receptor-beta expression or serum hormonal profiles in men at high risk of prostate cancer

The purpose of this study was to determine the effects of soy protein isolate consumption on circulating hormone profiles and hormone receptor expression patterns in men at high risk for developing advanced prostate cancer. Fifty-eight men were randomly assigned to consume 1 of 3 protein isolates containing 40 g/d protein: 1) soy protein isolate (SPI+) (107 mg/d isoflavones); 2) alcohol-washed soy protein isolate (SPI-) (<6 mg/d isoflavones); or 3) milk protein isolate (0 mg/d isoflavones). For 6 mo, the men consumed the protein isolates in divided doses twice daily as a partial meal replacement. Serum samples collected at 0, 3, and 6 mo were analyzed for circulating estradiol, estrone, sex hormone-binding globulin, androstenedione, androstanediol glucuronide, dehydroepiandrosterone sulfate, dihydrotestosterone, testosterone, and free testosterone concentrations by RIA. Prostate biopsy samples obtained pre- and postintervention were analyzed for androgen receptor (AR) and estrogen receptor-beta expression by immunohistochemistry. At 6 mo, consumption of SPI+ significantly suppressed AR expression but did not alter estrogen receptor-beta expression or circulating hormones. Consumption of SPI- significantly increased estradiol and androstenedione concentrations, and tended to suppress AR expression (P = 0.09). Although the effects of SPI- consumption on estradiol and androstenedione are difficult to interpret and the clinical relevance is uncertain, these data show that AR expression in the prostate is suppressed by soy protein isolate consumption, which may be beneficial in preventing prostate cancer.

Clinical and biological activity of soy protein powder supplementation in healthy male volunteers

PURPOSE

To determine if a commonly used soy protein supplement exhibits biological activity in vivo and in vitro, we evaluated an over-the-counter soy protein powder supplement using blood from healthy male volunteers and in an estrogen receptor in vitro assay.

SUBJECTS AND METHODS

We recruited healthy male volunteers 18 years of age or older that were in good health. Treatment consisted of consuming two scoops (56 g) of pure soy protein powder (Puritan's Pride, Oakdale, NY) daily for 28 days. Serum testosterone and luteinizing hormone (LH) levels were collected on days -7, 0, 14, and 28 of therapy, and day 42. A reporter estrogen receptor (ER) assay was used to determine the effect on ER-beta and ER-alpha in vitro.

RESULTS

Twelve subjects were enrolled with a mean age of 32.25 years (range 25 to 47). Serum testosterone decreased 19%(+/-22%) during the 4-week use of soy protein powder (P = 0.021) and increased within 2 weeks after we discontinued soy protein powder. Serum LH concentrations decreased during the 4-week use of soy protein powder then increased within 2 weeks after we stopped the soy protein powder, but the changes did not reach statistical significance (P = 0.20). Soy protein powder was found to induce agonist activity to ER-beta using a reporter estrogen receptor assay in yeast.

CONCLUSION

Soy protein powder decreases serum testosterone levels in healthy men and acts as an ER-beta agonist; the significance of this biological effect with respect to cancer prevention needs further study.

Consumption of Lactobacillus acidophilus and Bifidobacterium longum does not alter phytoestrogen metabolism and plasma hormones in men: a pilot study

OBJECTIVE

The aim of this study was to determine whether equol excretion status and plasma hormone and leptin concentrations can be influenced by consumption of a probiotic supplement. A secondary focus was to investigate whether male equol excretors have a hormone profile consistent with reduced prostate cancer risk.

DESIGN

The design was a randomized, single-blinded, placebo-controlled, parallel-arm trial.

SUBJECTS

Thirty-one (31) of the initially enrolled 39 subjects, 18 to 37 years old, completed all study requirements.

INTERVENTION

Subjects consumed either probiotic capsules (containing Lactobacillus acidophilus and Bifidobacterium longum) or placebo capsules for 2 months. Fasting plasma concentrations of testosterone (T), dihydrotestosterone (DHT), androstanediol glucuronide (AAG), androstenedione (A), dehydroepiandrosterone sulfate (DHEAS), sex hormone-binding globulin (SHBG), and leptin were measured on days 1 and 57. Urinary excretion of genistein, glycitein, daidzein, O-desmethylangolensin (O-Dma), and equol was measured on days 4 and 61 following a 4-day soy challenge.

RESULTS

Probiotic consumption did not significantly alter equol excretor status, plasma hormone, or leptin concentrations in these subjects. At baseline, there were no differences in plasma hormone concentrations between equol excretors and nonexcretors; however, the low number of equol excretors included in this study limits the strength of this finding.

CONCLUSIONS

The 2-month intervention with probiotic capsules did not significantly alter equol excretion, plasma hormone, or leptin concentrations in these subjects. A secondary finding was that male equol excretors in this study did not exhibit a hormone profile consistent with reduced prostate cancer risk, although this result should be interpreted with caution.

Plasma and urinary phyto-oestrogens as biomarkers of intake: validation by duplicate diet analysis

Estimating intake of phyto-oestrogens (PO) is difficult because there is inadequate information on the PO content of foods. Development of a biomarker of intake is therefore necessary for carrying out epidemiological studies. We aimed to validate a newly constructed PO database, containing more than 600 values assigned to foods by using duplicate diet analysis, and to investigate the relationships between measured PO intake, urinary excretion and plasma concentrations of PO. Fourteen subjects with estimated dietary intakes of PO ranging from 0 to 44mg/d, measured by 7d weighed intake, completed a duplicate diet collection over 24h. Concurrently, a 24h urine collection, validated using p-aminobenzoic acid, was obtained and one timed spot plasma sample taken. Duplicate diets, complete urine collections and plasma samples were analysed for total genistein and daidzein using liquid chromatography–MS to determine PO intake. The potential for 24h urinary excretion and plasma PO concentrations to reflect dietary intake was investigated. Mean estimated and measured dietary PO intakes were 12·3 and 11·0mg/d respectively. The correlation between estimated intake and measured intake of PO was highly significant (r 0·98, P<0·001). Urinary excretion (24h) and plasma concentrations of PO were significantly related to measured dietary PO intake (r 0·97, P<0·001 and r 0·92, P<0·001 respectively). The relationship between 24h urinary PO excretion and timed plasma concentrations was also significant (r 0·99, P<0·001). These findings validate the PO database and indicate that 24h urinary excretion and timed plasma concentrations can be used as biomarkers of PO intake.

Serum prostate-specific antigen but not testosterone levels decrease in a randomized soy intervention among men

BACKGROUND

Low prostate cancer incidence and high soy intake in Asian countries suggest a possible protective effect of soy foods against prostate cancer. The goal of this pilot study was to evaluate the feasibility of a randomized, crossover soy trial among men and to investigate the effects of daily soy intake on serum prostate-specific antigen (PSA) and testosterone levels.

METHODS

We randomized 24 men to a high or a low soy diet for 3 months. After a 1-month washout period, the men crossed over to the other treatment. During the high soy diet, the men consumed two daily soy servings; during the low soy diet, they maintained their usual diet. During the entire study each man donated four blood samples and five overnight urine samples. Dietary compliance was assessed by soy calendars, 24-h dietary recalls, and urinary isoflavone excretion measured by high-pressure liquid chromatography with photodiode array detection. Blood samples were analyzed for serum testosterone and PSA by radioimmunoassay. When necessary, variables were log transformed. Two sample t-tests compared the two groups before each study period. Mixed models incorporating the repeated measurements were used to evaluate the effect of the soy diet on urinary isoflavone excretion and serum analytes.

RESULTS

Twenty-three men aged 58.7+/-7.2 years completed the study. The compliance with the study regimen was high according to self-reported soy food intake and urinary isoflavone excretion. No significant between-group and within-group differences were detected. During the high soy diet, dietary isoflavone intake and urinary isoflavone excretion increased significantly as compared to the low soy diet. A 14% decline in serum PSA levels (P=0.10), but no change in testosterone (P=0.70), was observed during the high soy diet in contrast to the low soy diet.

CONCLUSION

The high adherence as shown by three measures of compliance in this pilot trial demonstrated the feasibility of an intervention based on soy foods among free-living men.

Molecular effects of the isoflavonoid genistein in prostate cancer

Differences in diet have been proposed to be at least partially responsible for the low rate of prostate cancer in Asian populations compared with men in Western countries. One of the compounds that occurs in a greater quantity in the Eastern diet is genistein, an isoflavonoid found in high concentrations in serum after ingestion of soy-rich foods. Extensive molecular studies have been performed to determine its potential health benefits. The mechanism of action of genistein is complex and includes several cellular pathways. In addition to its estrogenic and/or antiestrogenic activities, genistein has been reported to inhibit steroidogenesis and block several protein tyrosine kinases, including epidermal growth factor receptor and src tyrosine kinases. Moreover, it arrests the cell cycle, induces apoptosis, and has antiangiogenic and antimetastatic properties and antioxidant activity. Herein, we review the current literature on the molecular mechanisms of genistein in relation to its effects on prostate cancer cells.

Role of diet in prostate cancer development and progression

Increasing evidence supports the important role of nutrition in cancer prevention, including prevention of prostate cancer. In this review, we summarize data for some of the most consistently observed dietary associations for prostate cancer incidence, briefly consider possible postdiagnostic effects of nutrition on prostate cancer progression/survival, discuss new but limited data on diet-gene interactions, and comment on current areas of controversy for future research focus. Potential protective dietary elements include tomatoes/lycopene, other carotenoids, cruciferous vegetables, vitamin E, selenium, fish/marine omega-3 fatty acids, soy, isoflavones and polyphenols; whereas milk, dairy, calcium, zinc at high doses, saturated fat, grilled meats, and heterocyclic amines may increase risk. It is important to note that randomized clinical trial data exist only for vitamin E, calcium, beta-carotene, and selenium (all of which suggest inverse or no association). Several genes, such as MnSOD, XRCC1, and GST, may modify the association of specific nutrients and foods with prostate cancer risk; and further research is warranted to confirm these initial observed relationships. Until further clinical trial data are available on specific supplements and prostate cancer prevention, it would be prudent to emphasize a diet consisting of a wide variety of plant-based foods and fish; this is similar to what is recommended (and what is more well established) for the primary prevention of heart disease.

Endocrine disrupting compounds and prostate cancer

Prostate cancer is a major health concern and is treated based on its hormone dependence. Agents that alter hormone action can have substantial biological effects on prostate cancer development and progression. As such, there is significant interest in uncovering the potential effects of endocrine disrupting compound (EDC) exposure on prostate cancer. The present review is focused on agents that alter hormone action in the prostate and how they may impact cancer growth or treatment.

Meta-analysis of soy food and risk of prostate cancer in men

There has been considerable interest in recent years in the role of soy in cancer etiology. The purpose of this meta-analysis was to evaluate epidemiologic studies available to date that related soy consumption to the risk of prostate cancer in men. We conducted a thorough Medline search for English-language publications, supplemented with hand-searching of articles' bibliographies and nonindexed medical and professional journals, on epidemiologic studies of soy and prostate cancer. We identified 2 cohort and 6 case-control studies that met the following criteria for meta-analysis: a study must have assessed soy as a food and provided a risk estimate (relative risk or odds ratio) and its 95% confidence interval. Data from the same study population appearing in different journals were only used once with the most recent publication chosen for the analysis. Studies on fermented soy food were not included. We conducted the meta-analysis using a random-effects model. An analysis of these studies yielded an overall risk estimate of 0.70 (95% CI = 0.59-0.83; p < 0.001). No publication bias was detected. In summary, results of the analysis showed that consumption of soy food was associated with a lower risk of prostate cancer in men.

Polymorphisms in the CYP19 gene may affect the positive correlations between serum and urine phytoestrogen metabolites and plasma androgen concentrations in men

Phytoestrogens have been hypothesized to protect against prostate cancer via modulation of circulating androgen concentrations. We conducted a cross-sectional study of 267 men in the Norfolk arm of the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort with 2 aims: first, to investigate the association between phytoestrogen exposure (measured from diet, urine, and serum) and plasma concentrations of sex hormone-binding globulin (SHBG), androstanediol glucuronide, testosterone and Free Androgen Index (FAI); and second, whether the association may be modified by polymorphisms in CYP19 and SHBG genes. Dietary daidzein and genistein intakes were obtained from food diaries and computed using an in-house food composition database. Urinary and serum concentrations of 3 isoflavones (daidzein, genistein, glycitein), 2 daidzein metabolites O-desmethylangolensin (O-DMA) and 2 lignan metabolites (enterodiol and enterolactone) were measured using mass spectrometry. There was no association between dietary, urinary, and serum phytoestrogens and plasma SHBG concentrations. Enterolactone was positively associated with plasma androstanediol glucuronide concentrations (urinary enterolactone: r = 0.127, P = 0.043; serum enterolactone: r = 0.172, P = 0.006) and FAI (urinary enterolactone: r = 0.115, P = 0.067; serum enterolactone: r = 0.158, P = 0.011). Both urinary and serum equol were associated with plasma testosterone (urinary equol: r = 0.332, P = 0.013; serum equol: r = 0.318, P = 0.018) and FAI (urinary equol: r = 0.297, P = 0.027; serum equol: r = 0.380, P = 0.004) among men with the TT genotype but not the CC or CT genotypes (r = -0.029 to -0.134, P = 0.091-0.717) for the CYP19 3'untranslated region (UTR) T-C polymorphism. Urinary and serum enterolactone showed similar genotype-dependent associations with testosterone but not with FAI. In this first study on phytoestrogen-gene associations in men, we conclude that enterolactone and equol are positively associated with plasma androgen concentrations, and interactions with CYP19 gene may be involved.

Calcaneum broadband ultrasound attenuation relates to vegetarian and omnivorous diets differently in men and women: an observation from the European Prospective Investigation into Cancer in Norfolk (EPIC-Norfolk) population study

Vegetarian diets have been suggested to be beneficial for bone health due to increased consumption of plant foods, including soya, or reduced consumption of meat. However, meat may also be beneficial for bone health. The evidence relating diet to bone health is based largely on studies of women, often in those at high risk of osteoporosis. Few studies have investigated dietary inter-relationships in men as well as women from general populations. We examined broadband ultrasound attenuation (BUA) of the calcaneum, using a CUBA clinical instrument, in 6,369 men and 5,379 postmenopausal women. The population was divided into four groups according to vegetarian status and frequency of soya consumption, which was defined by response to a food frequency questionnaire that estimates frequency of consumption of food types over the year prior to completion. Regular soya consumers were defined as those who ate soya products with a frequency of between once a day and once a week. Calcaneum BUA in vegetarian men was significantly lower than omnivores by approximately 6% (5 dB/MHz) and was 15% (13.6 dB/MHz) lower in those who were also regular soya consumers. This difference remained after adjustment for age, height, weight, smoking habit, physical activity, selected foods and nutrients and exclusion of those with a prior history of osteoporosis, fractures or cancer. Calcaneum BUA in omnivorous men with regular soya consumption was not lower than the remaining population. In women, there were no significant differences by usual dietary pattern. This surprising finding indicates that regular soya intake is not associated with better bone indices in vegetarian men. The difference in BUA was not explained by the known common covariates; however, it is possible that other aspects of lifestyle associated with these eating behaviors might explain this observation. Plausible mechanisms exist for our findings; soya contains phytoestrogens, likened to naturally occurring estrogens, and meat has been shown to influence levels of IGF-1 and sex hormone binding globulin, which may be related to bone health. Our findings emphasize the need for further research and investigation into dietary inter-relationships and bone health and the effects of vegetarian status, including consumption of soya-based foods, in men as well as women.

Soy protein isolates of varying isoflavone content exert minor effects on serum reproductive hormones in healthy young men

Inverse associations between soy and prostate cancer and the contribution of hormones to prostate cancer prompted the current study to determine whether soy protein could alter serum hormones in men. Thirty-five men consumed milk protein isolate (MPI), low-isoflavone soy protein isolate (SPI) (low-iso SPI; 1.64 +/- 0.19 mg isoflavones/d), and high-iso SPI (61.7 +/- 7.35 mg isoflavones/d) for 57 d each in a randomized crossover design. Twenty-four-hour urine samples indicated that urinary isoflavones were significantly increased by the high-iso SPI relative to the low-iso SPI and MPI. Serum collected on d 1, 29, and 57 of each treatment revealed that dihydrotestosterone (DHT) and DHT/testosterone were significantly decreased by the low-iso SPI [9.4% (P = 0.036) and 9.0% (P = 0.004), respectively] and the high-iso SPI [15% (P = 0.047) and 14% (P = 0.013), respectively], compared with the MPI at d 57. Other significant effects included a decrease in testosterone by the low-iso SPI relative to the MPI (P = 0.023) and high-iso SPI (P = 0.020) at d 29; an increase in dehydroepiandrosterone sulfate by the low-iso SPI relative to the MPI at d 29 (P = 0.001) and relative to the MPI (P = 0.0003) and high-iso SPI (P = 0.005) at d 57; and increases in estradiol and estrone by the low-iso SPI relative to the MPI at d 57 (P = 0.010 and P = 0.005, respectively). In conclusion, soy protein, regardless of isoflavone content, decreased DHT and DHT/testosterone with minor effects on other hormones, providing evidence for some effects of soy protein on hormones. The relevance of the magnitude of these effects to future prostate cancer risk requires further investigation.

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.

Preventing diseases of the prostate in the elderly using hormones and nutriceuticals

The prostate has only one function, namely to secrete fluid containing substances that are needed for reproduction. This requires an extremely high concentration of androgens in the tissues. Benign prostatic hypertrophy (BPH) seems to be related to the long-term exposure of the prostate to the strong androgen 5alpha-dihydrotestosterone (DHT) and, possibly, to estrogens. The relation between prostate cancer and androgens is suggested to be U-shaped, with both extremes of androgen concentrations being associated with increased risk of invasive cancer. In the treatment of patients with BPH, the lipidic liposterolic extracts of Serenoa repens were as effective as the pharmaceutical inhibitors of the 5alpha-reductase enzyme or alpha1-adrenergic blockers in relieving urinary symptoms. In addition to moderately inhibiting the 5alpha-reductase activity, Serenoa seems to exert anti-inflammatory and complementary cellular actions with beneficial effects on the prostate. Unlike the pharmaceutical 5alpha-reductase inhibitors, finasteride and dutasteride, Serenoa does not suppress serum PSA, facilitating the follow-up and the early detection of prostate cancer. We suggest a strategy to prevent prostate cancer that aims at providing men with partial androgen deficiency correct testosterone substitution with a sustained release buccal bio-adhesive tablet. In addition, food supplementation with extracts of Serenoa repens and a combination of the antioxidants selenium, (cis)-lycopene and natural vitamin E, together with fish oil rich in long-chain polyunsaturated essential fatty acids of the omega-3 group seems warranted. Clearly, a holistic approach including careful clinical and biological monitoring of the aging man and his prostate remains mandatory.

Phyto-oestrogens, their mechanism of action: current evidence for a role in breast and prostate cancer

The incidence of hormone-dependent cancers, such as those of the breast and prostate, is much lower in Eastern countries such as China and Japan in comparison with the Western world. Diet is believed to have a major effect on disease risk and one group of compounds, the phyto-oestrogens, which are consumed in large amounts in Asian populations, have been implicated in cancer protection. This view follows the finding that plasma and urinary levels of phyto-oestrogens are much higher in areas where cancer incidence is low in comparison with areas of high cancer incidence. The phyto-oestrogens are comprised of two main groups; the isoflavones and lignans. Of the isoflavones, genistein and daidzein have been the most widely studied. These compounds have been shown to possess anticancer properties; however their precise mechanism of action remains to be elucidated. In comparison, few studies have investigated the effects of lignans in breast and prostate cancer. In vitro studies have shown that genistein exerts biphasic effects on cancer cell growth, stimulating growth at low concentrations (<10 microm) and inhibiting growth at high concentrations (>10 microm), which suggests that low phyto-oestrogen levels may stimulate cancer growth in vivo. Plasma phyto-oestrogen concentrations of >10 microm cannot be achieved by dietary intake and therefore the timing of exposure to phyto-oestrogens may be of the utmost importance in determining their chemopreventive effects. The present paper reviews the effects of phyto-oestrogens on breast and prostate cancer in vivo and in vitro and discusses possible mechanisms of action via which these compounds may exert their effects.

Isoflavones for prevention of cancer, cardiovascular diseases, gynecological problems and possible immune potentiation

Japanese women show low incidence of and mortality from breast cancer, cardiovascular disease and climacteric symptoms compared to Caucasians. High soy bean intake is considered to attribute to that, but it is not clear whether soy protein itself or isoflavones (IFs) mixed in the soy protein has such effects. Presence of IFs in soy beans was varied by site, so we made IF-rich tablets from daidzein-rich soy germ (hypocotyl) for intervention studies. Our intervention study on young women by using the IF-rich tablet (20 and 40 mg/day) showed slight elongation of the menstrual cycle, but no adverse effects occurred. Intervention study on climacteric women showed improvement of bone density, hypertension and climacteric symptoms. Health effects of IFs on cancer occurrence, cardiovascular diseases, gynecological problems and possible immune potentiation are reviewed from functional aspects.

Infant feeding with soy formula milk: effects on the testis and on blood testosterone levels in marmoset monkeys during the period of neonatal testicular activity

BACKGROUND

This study has addressed concerns about possible effects of feeding human infants soy formula milk (SFM).

METHODS

This is a feeding study in marmosets, using a mainly co-twin design. From 4-5 until 35-45 days of age, co-twin males were fed by hand with either standard (cow) formula milk (SMA = controls) or with SFM for approximately 8 h each day (2 h at weekends) and intake related to bodyweight. Blood samples were collected at 18-20 and at 35-45 days of age in 13 sets of co-twins plus two non-twin males per group and, at the later age, seven sets of co-twins were killed and the testes and pituitary gland fixed for cell counts.

RESULTS

Weight gain and formula intake were similar in both feeding groups. SMA-fed males had mean testosterone levels of 2.8-3.1 ng/ml, typical of the "neonatal testosterone rise", whereas SFM-fed males exhibited consistently lower mean levels (1.2-2.6 ng/ml); paired comparison in SMA-and SFM-fed co-twins at day 35-45 revealed 53-70% lower levels in 11 of 13 co-twins fed with SFM (P = 0.004). Further evidence for suppression of testosterone levels in SFM-fed males came from comparison of the frequency of low testosterone levels (<0.5 ng/ml). In historical controls aged 35-45 days, two out of 22 values were <0.5 ng/ml, a similar frequency as found in control SMA-fed males (one out of 15 values <0.5 ng/ml). In contrast, 12 out of 15 values for SFM-fed males were <0.5 ng/ml (P < 0.001). There was no consistent relationship between SFM intake/g and testosterone levels. Paradoxically, the mean number of Leydig cells per testis was increased by 74% (P < 0.001) in co-twins fed SFM, when compared with their SMA-fed brothers, whereas no significant changes were found in numbers of Sertoli and germ cells. Because of the lack of gonadotrophin assays, the number of immunopositive LHbeta and FSHbeta cells in the pituitary gland, and their ratio, were determined but no consistent difference was found between SMA- and SFM-fed twins.

CONCLUSIONS

Based on the average isoflavone content of the SFM brand used, intake of isoflavones was estimated at 1.6-3.5 mg/kg/day in the SFM-fed marmosets which is 40-87% of that reported in 4 month human infants fed on a 100% SFM diet. It is therefore considered likely that similar, or larger, effects to those shown here in marmosets may occur in human male infants fed with SFM. Whether the changes described result in longer-term effects is under investigation.

Hormonal effects of soy in premenopausal women and men

Over the past few years, there has been increasing interest in the possible hormonal effects of soy and soy isoflavone consumption in both women and men. Soy consumption has been suggested to exert potentially cancer-preventive effects in premenopausal women, such as increased menstrual cycle length and sex hormone-binding globulin levels and decreased estrogen levels. There has been some concern that consumption of phytoestrogens might exert adverse effects on men's fertility, such as lowered testosterone levels and semen quality. The studies in women have provided modest support for beneficial effects. One cross-sectional study showed serum estrogens to be inversely associated with soy intake. Seven soy intervention studies controlled for phase of menstrual cycle. These studies provided 32-200 mg/d of isoflavones and generally showed decreased midcycle plasma gonadotropins and trends toward increased menstrual cycle length and decreased blood concentrations of estradiol, progesterone and sex hormone-binding globulin. A few studies also showed decreased urinary estrogens and increased ratios of urinary 2-(OH) to 16alpha-(OH) and 2-(OH) to 4-(OH) estrogens. Soy and isoflavone consumption does not seem to affect the endometrium in premenopausal women, although there have been weak estrogenic effects reported in the breast. Thus, studies in women have mostly been consistent with beneficial effects, although the magnitude of the effects is quite small and of uncertain significance. Only three intervention studies reported hormonal effects of soy isoflavones in men. These recent studies in men consuming soyfoods or supplements containing 40--70 mg/d of soy isoflavones showed few effects on plasma hormones or semen quality. These data do not support concerns about effects on reproductive hormones and semen quality.

Lifestyle/dietary supplement partial androgen suppression and/or estrogen manipulation. A novel PSA reducer and preventive/treatment option for prostate cancer?

There is a large interest in prostate cancer prevention and/or slowing the progression of this disease via dietary/lifestyle/supplement interventions. Numerous mechanisms have been suggested as to how these interventions may lower PSA levels. However, it is possible that the primary mechanism of action is partial androgen suppression and/or estrogen manipulation.