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.
"breast tissue (Maskarinec et al., 2004; Maskarinec et al., 2009), increased number of breast tissue cells (Palomares et al., 2004), or increased estrogen circulating in the blood (Kurzer, 2002). The prevalence of hormone-dependent tumors such as breast or prostate cancer is significantly lower in Asia than in Western countries. "
[Show abstract][Hide abstract] ABSTRACT: Breast cancer is the second leading cause of cancer death among women and the third most common cancer. In this study, we investigated the chemoprevention efficacy of each of soy genistin, selenium or a combination of them against breast cancer. Seventy-five female rats were divided into five groups : control group (I); 7,12-dimethylbenz(a)anthracene (DMBA) group (II); DMBA treated with genistin group (III); DMBA treated with selenium group (IV); and DMBA treated with genistin combined with selenium group (V). The treatments were daily administered for 3 months. There were a significant decrease in body weight and serum total antioxidant, while a significant elevation in serum total sialic acid, carcinoembryonic antigen, prolactin, estradiol, nitric oxide, and malondialdhyde of DMBA injected rats compared with control group. Administration of genistin and selenium was associated with decreasing levels of tumorigenicity, endocrine derangement, and oxidative stress. Formation of breast carcinoma in DMBA-induced rats and abnormal changes were ameliorated in the rats treated with genistin/selenium or genistin alone. Supplementation of genistin alone or with selenium provided antioxidant defense with high-potential chemopreventive activity against DMBA-induced mammary tumors more than selenium alone.
Toxicology and Industrial Health 11/2011; 28(8):746-57. DOI:10.1177/0748233711422732 · 1.86 Impact Factor
"Genistein binds to and activates estrogen receptors, peroxisomeproliferators activated receptors, liver X receptors and estrogen related receptors. It was recognized very early that the chemical structure of genistein bears strong similarity to 17β-estradiol, and that genisten binds to estrogen receptors (ER) and to sex hormonebinding globulins (Klinge, 2000; Kuiper et al., 1998; Kurzer, 2002). A functional interaction of genistein with estrogen receptors, leading to stimulation of ER responsive genes was confirmed in experiments in vitro (Birt et al., 2001; Kostelac et al., 2003). "
"Importantly, it has been observed in non-human primates that—as in women— reproductive impairment reverses following an improvement in psychological circumstances (e.g. if low status animals become high ranking; Shively and Clarkson, 1994; Adams et al., 1985). Soy isoflavones are estrogen-like compounds found in soy protein and widely used in dietary supplements (Kurzer, 2002). Because they bind to estrogen receptors, soy isoflavones could alter endogenous hormonal activity, ovarian hormone profiles, menstrual cyclicity and ultimately health (Miksicek, 1994; Wang et al., 1996). "
[Show abstract][Hide abstract] ABSTRACT: 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.
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.
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.
(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.
Human Reproduction 10/2010; 25(12):3083-94. DOI:10.1093/humrep/deq288 · 4.57 Impact Factor
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