High Levels Of Phytoestrogens Research Articles

MON-079 Prepubertal Gynecomastia Secondary to Excessive Soy Consumption

Enlargement of breast tissue in males, or gynecomastia, is a rare condition in prepubescent boys. While the majority of cases are idiopathic, we describe an 8-year-old patient who developed unilateral gynecomastia secondary to marked dietary soy consumption. Soy products, particularly those consumed by our patient, contain high levels of phytoestrogens which have been documented in limited case studies to contribute to abnormal development of breast tissue in adolescent and adult males. To our knowledge, this is the first documented case of gynecomastia occurring in a prepubescent patient resulting from excessive intake of dietary soy. Importantly, we also report a complete resolution of gynecomastia upon exclusion of dietary products containing significant amounts of soy. While soybeans and soy-derived products can be an important source of nutrition for some, those with abnormal sensitivity to phytoestrogens may benefit from limiting dietary soy consumption to avoid potential adverse effects, including gynecomastia.

Nutrition research in cognitive impairment/dementia, with a focus on soya and folate.

Observational studies and treatment trials investigating nutrition and cognitive function, with a focus on folate and soya and dementia, were reviewed. Data suggested that effects of folic acid based interventions may only be shown before cognitive decline is evident and/or if people are folate deficient. In older people in Indonesia, Hawai'i and China, tofu, which can contain high levels of phytoestrogens, was found to increase dementia risk. This association was not mediated by a vegetarian diet, socioeconomic status, formaldehyde, thyroid function, or loss of teeth. On the other hand, human observational and animal treatment studies suggested that tempe, a fermented soya product containing phytoestrogens and folate, reduced dementia risk and improved memory. High oestrogen levels were found to increase dementia risk in older women. However, in women with adequate serum folate, high oestrogen levels did not confer additional dementia risk and may protect ageing neurons. In conclusion, reviews seem to suggest that folic acid interventions are only effective on cognitive outcomes in people who are folate deficient and do not have cognitive impairment. Frequent consumption of tofu may have detrimental effects on memory and increase dementia risk in older East Asian people, while tempe may reduce these risks. Possibly folate in tempe offsets the potential negative effects of oestrogenic compounds on ageing neurons.

Phytoestrogens for menopausal vasomotor symptoms.

Vasomotor symptoms, such as hot flushes and night sweats, are very common during the menopausal transition. Hormone therapy has traditionally been used as a highly effective treatment, but concerns about increased risk of some chronic diseases have markedly increased the interest of women in alternative treatments. Some of the most popular of these treatments are foods or supplements enriched with phytoestrogens-plant-derived chemicals that have estrogenic action. To assess the efficacy, safety and acceptability of food products, extracts and dietary supplements containing high levels of phytoestrogens when compared with no treatment, placebo or hormone therapy for the amelioration of vasomotor menopausal symptoms (such as hot flushes and night sweats) in perimenopausal and postmenopausal women. Searches targeted the following electronic databases: the Cochrane Menstrual Disorders and Subfertility Group Specialised Register of randomised trials (29 July 2013), the Cochrane Register of Controlled Trials (CENTRAL; 29 July 2013), MEDLINE (inception to 29 July 2013), EMBASE (inception to 29 July 2013), AMED (1985 to 29 July 2013), PsycINFO (inception to 29 July 2013) and CINAHL (inception to 29 July 2013). Attempts were made to access grey literature by sending letters to pharmaceutical companies and performing searches of ongoing trial registers. Reference lists of included trials were also searched. Studies were included if they were randomised, included perimenopausal or postmenopausal participants with vasomotor symptoms (hot flushes or night sweats), lasted at least 12 weeks and provided interventions such as foods or supplements with high levels of phytoestrogens (not combined with other herbal treatments). Trials that included women who had breast cancer or a history of breast cancer were excluded. Selection of trials, extraction of data and assessment of quality were undertaken by at least two review authors. Most trials were too dissimilar for their results to be combined in a meta-analysis, so these findings are provided in narrative 'Summary of results' tables. Studies were grouped into broad categories: dietary soy, soy extracts, red clover extracts, genistein extracts and other types of phytoestrogens. Five trials used Promensil, a red clover extract; results of these trials were combined in a meta-analysis, and summary effect measures were calculated. A total of 43 randomised controlled trials (4,364 participants) were included in this review. Very few trials provided data suitable for inclusion in a meta-analysis. Among the five trials that yielded data assessing the daily frequency of hot flushes suitable for pooling, no significant difference overall was noted in the incidence of hot flushes between participants taking Promensil (a red clover extract) and those given placebo (mean difference (MD) -0.93, 95% confidence interval (CI) -1.95 to 0.10, I(2) = 31%). No evidence indicated a difference in percentage reduction in hot flushes in two trials between Promensil and placebo (MD 20.15, 95% CI -12.08 to 52.38, I(2) = 82%). Four trials that were not combined in meta-analyses suggested that extracts with high (> 30 mg/d) levels of genistein consistently reduced the frequency of hot flushes. Individual results from the remaining trials were compared in broad subgroups such as dietary soy, soy extracts and other types of phytoestrogens that could not be combined. Some of these trials found that phytoestrogen treatments alleviated the frequency and severity of hot flushes and night sweats when compared with placebo, but many trials were small and were determined to be at high risk of bias. A strong placebo effect was noted in most trials, with a reduction in frequency ranging from 1% to 59% with placebo. No indication suggested that discrepant results were due to the amount of isoflavone in the active treatment arm, the severity of vasomotor symptoms or trial quality factors. Also, no evidence indicated that these treatments caused oestrogenic stimulation of the endometrium or the vagina or other adverse effects when used for up to two years. No conclusive evidence shows that phytoestrogen supplements effectively reduce the frequency or severity of hot flushes and night sweats in perimenopausal or postmenopausal women, although benefits derived from concentrates of genistein should be further investigated.

Phytoestrogens in menopausal supplements induce ER-dependent cell proliferation and overcome breast cancer treatment in an in vitro breast cancer model

Breast cancer treatment by the aromatase inhibitor Letrozole (LET) or Selective Estrogen Receptor Modulator Tamoxifen (TAM) can result in the onset of menopausal symptoms. Women often try to relieve these symptoms by taking menopausal supplements containing high levels of phytoestrogens. However, little is known about the potential interaction between these supplements and breast cancer treatment, especially aromatase inhibitors. In this study, interaction of phytoestrogens with the estrogen receptor alpha and TAM action was determined in an ER-reporter gene assay (BG1Luc4E2 cells) and human breast epithelial tumor cells (MCF-7). Potential interactions with aromatase activity and LET were determined in human adrenocorticocarcinoma H295R cells. We also used the previously described H295R/MCF-7 co-culture model to study interactions with steroidogenesis and tumor cell proliferation. In this model, genistein (GEN), 8-prenylnaringenin (8PN) and four commercially available menopausal supplements all induced ER-dependent tumor cell proliferation, which could not be prevented by physiologically relevant LET and 4OH-TAM concentrations. Differences in relative effect potencies between the H295R/MCF-7 co-culture model and ER-activation in BG1Luc4E2 cells, were due to the effects of the phytoestrogens on steroidogenesis. All tested supplements and GEN induced aromatase activity, while 8PN was a strong aromatase inhibitor. Steroidogenic profiles upon GEN and 8PN exposure indicated a strong inhibitory effect on steroidogenesis in H295R cells and H295R/MCF-7 co-cultures. Based on our in vitro data we suggest that menopausal supplement intake during breast cancer treatment should better be avoided, at least until more certainty regarding the safety of supplemental use in breast cancer patients can be provided.

Effects of phytoestrogens on sex reversal of Nile tilapia (Oreochromis niloticus) larvae fed diets treated with 17α-Methyltestosterone

Two consecutive experiments were carried out to investigate the effects of phytoestrogens on sex reversal of Nile tilapia (Oreochromis niloticus) larvae. Experiment 1 investigated the effects of phytoestrogen contents of soybean meal (SBM) on sex ratio. Nile tilapia larvae (0.01g/fish) were fed isonitrogenous (35% crude protein) and isocaloric (19MJ/kg) diets containing fishmeal (FM) or SBM as protein sources, each with or without supplementation of 17α-methyltestosterone (MT) at 60mg/kg diet, for 28days. The control, SBM-based diet produced significantly higher percentage of females (77%) than the FM-based diet (52%). The addition of MT to SBM resulted in a significant reduction in percentage of females (31%), however, this percentage was significantly higher than that produced by FM-based diet treated with MT (only 3% females).The second experiment was carried out to verify the results of the first experiment by investigating the effects of different concentrations of pure, crystalline genistein and daidzein (the major phytoestrogens present in soybean) on sex reversal of Nile tilapia larvae fed on a FM-based diet treated with MT. The same FM-based diet used in experiment 1 was used in experiment 2, and treated with MT, and then divided into equal portions treated with genistein or daidzein at 0, 10, 20 and 30mg/kg diet. The diets were fed to Nile tilapia larvae for 28days. The control, hormone-free diet produced almost equal ratio of females and males (0.96:1). The addition of MT significantly increased the percentage of males. The percent of males was sharply reduced with increasing daidzein and genistein concentrations in the diets. These results revealed that phytoestrogen contents of SBM have estrogenic effects on Nile tilapia larvae. Therefore, soybean meal and other plant protein sources containing high levels of phytoestrogens should be avoided as protein sources for Nile tilapia larvae during sex reversal treatments.

Diverse animal models to examine potential role(s) and mechanism of endocrine disrupting chemicals on the tumor progression and prevention: Do they have tumorigenic or anti-tumorigenic property?

Acting as hormone mimics or antagonists in the interaction with hormone receptors, endocrine disrupting chemicals (EDCs) have the potentials of disturbing the endocrine system in sex steroid hormone-controlled organs and tissues. These effects may lead to the disruption of major regulatory mechanisms, the onset of developmental disorders, and carcinogenesis. Especially, among diverse EDCs, xenoestrogens such as bisphenol A, dioxins, and di(2-ethylhexyl)phthalate, have been shown to activate estrogen receptors (ERs) and to modulate cellular functions induced by ERs. Furthermore, they appear to be closely related with carcinogenicity in estrogen-dependant cancers, including breast, ovary, and prostate cancers. In in vivo animal models, prenatal exposure to xenoestrogens changed the development of the mouse reproductive organs and increased the susceptibility to further carcinogenic exposure and tumor occurence in adults. Unlike EDCs, which are chemically synthesized, several phytoestrogens such as genistein and resveratrol showed chemopreventive effects on specific cancers by contending with ER binding and regulating normal ER action in target tissues of mice. These results support the notion that a diet containing high levels of phytoestrogens can have protective effects on estrogen-related diseases. In spite of the diverse evidences of EDCs and phytoestrogens on causation and prevention of estrogen-dependant cancers provided in this article, there are still disputable questions about the dose-response effect of EDCs or chemopreventive potentials of phytoestrogens. As a wide range of EDCs including phytoestrogens have been remarkably increasing in the environment with the rapid growth in our industrial society and more closely affecting human and wildlife, the potential risks of EDCs in endocrine disruption and carcinogenesis are important issues and needed to be verified in detail.

High Tofu Intake Is Associated with Worse Memory in Elderly Indonesian Men and Women

Background/Aims: Cell culture studies suggest that phytoestrogens, abundant in soy products such as tempe and tofu, could protect against cognitive decline. Paradoxically, the Honolulu Asia Aging Study reported an increased risk for cognitive impairment and other dementia markers with high tofu (soybean curd) intake. Methods: A cross-sectional study was carried out in 2 rural sites (Borobudur and Sumedang) and 1 urban site (Jakarta) among mainly Javanese and Sundanese elderly (n = 719, 52–98 years of age). Memory was measured using a word learning test sensitive to dementia and soy consumption was assessed using Food Frequency Questionnaire items. Results: High tofu consumption was associated with worse memory (β = –0.18, p < 0.01, 95% CI = –0.34 to –0.06), while high tempe consumption (a fermented whole soybean product) was independently related to better memory (β = 0.12, p < 0.05, 95% CI = 0.00–0.28), particularly in participants over 68 years of age. Fruit consumption also had an independent positive association. The analyses were controlled for age, sex, education, site and intake of other foods. Conclusion: The results for tofu consumption as a risk factor for low memory function may tie in with the Honolulu Asia Aging Study data. It is unclear whether these negative associations could be attributed to potential toxins or to its phytoestrogen levels. Estrogen (through which receptors phytoestrogens can exert effects) was found to increase dementia risk in women over 65 years of age. Tempe contains high levels of phytoestrogens, but (due to fermentation) also exhibits high folate levels which may exert protective effects. Future studies should validate these findings and investigate potential mechanisms.

Gender-specific modulation of markers for premalignancy by nutritional soy and calcium in the mouse colon.

Sporadic colorectal cancer develops as a multistep process during decades of latency. Multiple factors, in particular nutrition, influence progression. Both nutritional calcium and soy are known to reduce sporadic cancer incidence. Soy contains high levels of phytoestrogens. Among them genistein is recognized as an antioxidant and cell-cycle inhibitor. However, timing and length of consumption of genistein as well as gender- and colon site-specific activity may result in beneficial or detrimental effects. We therefore evaluated the effect in mice of a basic AIN76A diet containing 20% soy as main protein source fed for 1 or 2 generations. In another set of animals, normal calcium levels (0.5%) were replaced by low calcium (0.04%) with or without supplementation of genistein (0.04%). Expression of the vitamin D receptor, cyclooxygenase (COX)-2, proapoptotic Bak and antiapoptotic Bcl-2 protein, as well as estrogen receptor (ER)-alpha and ER-beta mRNA were evaluated. Results were identical whether soy was fed for 1 or 2 generations. Soy decreased Bak and increased COX-2 and ER-alpha expression site-specifically in female mice. Vitamin D receptor protein was reduced only in males. In animals fed 0.04% dietary calcium, COX-2 protein was increased mainly in females, but supplementation of genistein to the diet lowered COX-2 expression significantly in both genders. Our results suggest that genistein counteracts the induction of a marker of colonic premalignancy by low nutritional calcium in both genders. However, soy itself enhances COX-2 and reduces Bak, but only in females. This suggests detrimental activity of an unknown component of soy triggered by a high-estrogen background.

Children’s Health: Sour News for Soy Formula?

Naturally occurring phytoestrogens have been intensively studied for health effects in adults. However, studies of soy formula, which delivers high levels of phytoestrogens to infants, have not extended much beyond ensuring that babies are growing and developing normally. Still, soy formula has been considered a safe alternative to milk-based formulas for some 40 years. Recent studies from the University of Illinois at Urbana–Champaign now show that the soy phytoestrogen genistein can alter intestinal cell proliferation and migration, with unknown effects for infants fed soy formula. “We are feeding infants soy formula as their sole source of nutrition for the first four to six months of life, a period of time when many systems are immature and undergoing development,” says Sharon Donovan, a professor of nutrition involved in both studies. It is known that infants metabolize genistein and can have some circulating level of the bioactive form. But whether the effects are good, bad, or even measurable is unknown and fiercely debated. “Why [soy formula] has not received more research attention, I’m not sure,” says Retha Newbold, an NIEHS toxicologist who has investigated the developmental effects of genistein and other estrogenic substances for more than 25 years. In the first Illinois study, published in the June 2004 Journal of Nutrition, researchers exposed human intestinal cells to varying doses of genistein and noted effects on cell numbers, DNA replication, apoptosis, and cell cycle. At low doses, genistein acted as a weak estrogen and stimulated cell growth; at high doses, the compound inhibited proliferation and altered cell cycle dynamics. This biphasic response correlates with how genistein is thought to exert its effects. In the other study, published in the February 2005 Pediatric Research, 24 2-day-old piglets were divided into three dietary groups for eight days, receiving plain sow milk replacer or replacer with either a low or high dose of genistein. The high-dose piglets had circulating concentrations of genistein on par with those of soy formula–fed infants. At 10 days of age, there were no significant differences in weight gain, intestinal length or growth, nutrient uptake, or digestive enzyme activity among the piglets. However, there was a 50% decrease in intestinal cell proliferation and a 20% decrease in cell migration associated with the high genistein dose. Donovan cautions that it’s premature to draw conclusions about negative or positive effects of infant soy formula. “This is what we see when we look at genistein alone,” she says, “but what happens when you look at a whole soy formula?” More than 20 million American infants have been fed soy formula in the last 25 years, and their growth and development have been equal to that of infants fed milk-based formula, according to Thomas Badger, director and senior investigator at the Arkansas Children’s Nutrition Center in Little Rock. “If there have been no problems in more than twenty million people exposed to soy formula, then there is no human evidence of a problem,” says Badger. Still, many researchers believe that more information is needed about the safety of infant soy formula. Phytoestrogen doses comparable to what infants receive through soy formula have been shown to cause cancer in some animal studies if given before puberty. “I think too little is known to conclude that soy formula is safe for the general infant population,” says Newbold.

Phytoestrogen genistein and its pharmacological interactions with synthetic endocrine-active compounds.

Phytoestrogens are plant-derived compounds with estrogen-like activities. Certain foods such as soy-derived products are known to have high levels of phytoestrogens, and about 25% of commercial infant formulas used in the United States are soy-based. One of the most important phytoestrogens is the isoflavone genistein. Human exposures to genistein occur through normal dietary intake and through the use of genistein or other isoflavone extracts as nutritional supplements. Among the issues raising concerns about human exposure to phytoestrogens is how such exposure may affect responsiveness and sensitivity of the exposed subjects to other xenobiotics, particularly drugs and environmental chemicals with estrogenic or other endocrine activities. This article describes our recent studies on the developmental effects of dietary genistein in rats and its potential to interact with the toxicology of the endocrine-active pesticide methoxychlor. Data from our studies demonstrated that genistein is capable of altering the toxicological behaviors of methoxychlor and likely other endocrine active compounds as well. The complexities of such interactions are difficult to predict based on their in vitro steroid receptor reactivities.

Modulation of mammary gland development in prepubertal male rats exposed to genistein and methoxychlor.

The estrogenic isoflavone genistein is a common dietary component that has been shown to affect reproductive development in experimental animals at high doses. The objective of the present study was to examine interactions of genistein and the hormonally active pesticide methoxychlor on mammary gland development in juvenile rats. Timed-pregnant Sprague-Dawley rats were fed a soy- and alfalfa-free diet containing different combinations of genistein (300 and 800 ppm) and methoxychlor (800 ppm). Rats were fed these diets starting on gestation day (GD)1 and continuing through pregnancy and lactation until postnatal day (PND) 22, when the pups were killed. Inguinal mammary glands from both female and male pups were processed as whole-mount preparations for morphometric analysis. The total glandular area and the numbers of branch points, lateral buds, and terminal end buds in the male rats were found to be significantly greater in the groups exposed to methoxychlor than those exposed to genistein only. These effects were not observed in the female rats. In the male rats, methoxychlor had the most prominent effect on elongating the glandular ducts, while genistein enhanced the ductile branching. The 2 compounds in combination promoted the development of alveolar-lobular structure, an effect not observed with either compound alone. Immunostaining for proliferating cell nuclear antigen revealed a high percentage of immunopositive cells in the mammary epithelia of the males exposed to methoxychlor and genistein (800 ppm) compared to the controls. While no significant changes in serum levels of mammotrophic hormones were detected, increased immunostaining for insulin-like growth factor-1 receptor, estrogen receptor alpha, and progesterone receptor in the genistein + methoxychlor group suggested that local factors involved in regulating mammary growth may have played a role in propagating the endocrine effects of these two compounds. These results indicated that the mammary glands of juvenile male rather than juvenile female rats may be more sensitive to certain endocrine-active compounds and that high levels of phytoestrogens have the potential to alter the toxicological behaviors of other hormone mimics.

Dietary genistein down-regulates androgen and estrogen receptor expression in the rat prostate

The incidence of clinically manifested prostate cancer is higher in the United States and Europe than in Asian countries. One of the major differences in lifestyle between these populations is the diet, with Asians consuming a greater amount of soy. Soy and genistein, the predominant isoflavone found in soy, inhibit prostate tumor development in animal models. The purpose of this study was to investigate the effect of dietary genistein on sex steroid receptor expression in the dorsolateral prostate, on circulating androgens, and the potential for toxicity in the male rat reproductive tract. Male Sprague-Dawley rats were fed 25 and 250 mg genistein/kg diet from conception until day 70 postpartum, or 250 and 1000 mg genistein/kg diet from day 56 to 70 postpartum. Exposure to genistein in the diet, starting at conception, resulted in down-regulated androgen receptor (AR), and estrogen receptors (ER)-α and -β mRNA expression in the dorsolateral prostate in a dose-dependent manner. Also, genistein fed to adult rats for 2 weeks reduced mRNA expression of AR, ER-α and ER-β in the dorsolateral prostate. ER-α protein levels were significantly reduced in animals fed 1000 mg genistein/kg diet compared to control animals. There were no significant alterations to male reproductive tract histomorphology or weights. We conclude that dietary genistein down-regulated expression of the AR and ER-α and -β in the rat prostate at concentrations comparable to those found in humans on a soy diet. Down-regulated sex steroid receptor expression may be responsible for the lower incidence of prostate cancer in populations on a diet containing high levels of phytoestrogens.

Effect of diet on lignans and isoflavonoid phytoestrogens in chimpanzees

Diphenolic compounds belonging to the classes of lignans and isoflavonoids have been identified in urine of man and animals, including the chimpanzee. Some of these compounds, formed by intestinal bacteria from plant lignans and phytoestrogens, have been shown in animal studies to exhibit biological activities that suggest they could function as cancer-protective compounds. The effect of diet on urinary excretion of these compounds in the adult male chimpanzee has been studied. It was found that the chimpanzees consuming their regular food excreted large amounts of the isoflavonoid phytoestrogens, equol (mean ± SE) (127.5 ± 34.0 nmol/mg cr.) and daidzein (20.7 ± 9.0 nmol/mg cr.) and the lignan, enterolactone(14.1 + 3.5 nmol/mg cr.). Small amounts of the lignan, enterodiol, (0.4 ± 0.2 nmol/mg cr.) were also excreted. On all other four test diets (high protein, high carbohydrate, high vegetable, and high fat), the excretion was less, particularly on a high fat diet where the excretion of all diphenolic compounds was reduced by more than 90% to a level observed in omnivorous human subjects or women with breast cancer. These results suggest that diet profoundly influences the excretion of both animal lignans and phytoestrogens in urine. Because non-human primates are particularly resistant to mammary and genital carcinoma on estrogen treatment, the present data suggest that the very high levels of phytoestrogens and lignans as found during exposure to the regular diet may partially account for why these primates are so resistant to hormonal manipulations to induce cancer.

Chemical Studies of Phytoestrogens and Related Compounds in Dietary Supplements: Flax and Chaparral

High-performance liquid chromatographic (HPLC) and mass spectrometric (MS) procedures were developed to determine lignans in flaxseed (Linum usitatissimum) and chaparral (Larrea tridentata). Flaxseed contains high levels of phytoestrogens. Chaparral has been associated with acute nonviral toxic hepatitis and contains lignans that are structurally similar to known estrogenic compounds. Both flaxseed and chaparral products have been marketed as dietary supplements. A mild enzyme hydrolysis procedure to prevent the formation of artifacts in the isolation step was used in the determination of secoisolariciresinol in flaxseed products. HPLC with ultraviolet spectral (UV) or MS detection was used as the determinative steps. HPLC procedures with UV detection and mass spectrometry were developed to characterize the phenolic components, including lignans and flavonoids, of chaparral and to direct fractionation studies for the bioassays.