The Contribution of Isoflavones in Menopausal Symptomatic as Alternative Treatment Option

Abstract

Menopause should be treated as a state of alteration of estrogen metabolism. It is characterized by a decrease in progesterone and an increase in estrogen followed by a drop in estrogen. The purpose of this study is to investigate the activity of hyaluronic acid 120 mg and isoflavones MF11RCE 80 mg, in the recovery of the symptoms of menopause and the treatment of its secondary complications such as osteoporosis, urogenital atrophy and accompanying urinary incontinence and vasomotor syndrome MF11RCE isoflavones are widely used to treat various disorders related mainly to women’s health and mainly osteoporosis and menopausal discomforts, based on epidemiological studies that brought the above diseases to a lower percentage, in populations with a high consumption of these plant estrogens. Isoflavones are derived from plants and structurally or functionally resemble endogenous-natural estrogens and their active metabolites. Therefore, they have significant estrogenic (agonistic/antagonistic) activity.

1. Introduction

Menopause is the permanent cessation of a woman’s period due to the exhaustion of the follicles, and loss of ovarian function and marks the end of a woman’s reproductive age occurring during the climacteric [1]. For a woman to be considered menopausal, menstruation should have stopped for a period of 12 months from the last menstrual period without any obvious physiological or pathological cause being responsible. The climacteric period may begin approximately four years before the last menstruation, on average 50.8 years. Duration of the symptoms may continue for several years after the last menstruation. The timing of menopause does not depend on the timing of menstruation and depends on family and racial factors [1]. The true causes of the process of ovarian failure leading to menopause have not been fully elucidated. An association of genes and menopause related to the biological mechanisms of DNA self-repair was certified. Two genes in particular, Chek1 and Chek2, according to experimental research in rodents, significantly affect fertility and menopause [2, 3]. The above genes are involved in cell apoptosis. Women who have a particular variant of Chek2, which renders the gene non-functional, are at menopause 3.5 years later compared to those in whom the specific gene is fully functional. According to researchers, the genetic modification of female mice, with the Chek2 gene deactivated, the survival time of the eggs of the experimental animals was longer. It is believed that if there was a drug that blocked Chek2, it would help women have more eggs at an older age [3, 4, 5, 6].

Hormone replacement therapy began, initially, as an attempt to alleviate specific symptoms (vasomotor) caused by changes in estrogen production during menopause.

However, when the long-term complications of menopause on women’s health became known, hormone replacement, in addition to being symptomatic, also acquired a preventive character. Classical hormone replacement therapy involves the administration of estrogens in combination with progesterone.

2. Phytoestrogens

They are a large group of plant substances whose chemical molecular structure contains a phenolic ring like estrogen. The main representatives are isoflavones and lignans. Isoflavones such as genistein are found in a number of plants such as green tea and possess both estrogenic and antiestrogenic properties like tamoxifen. Other plant substances are herbs and fruits such as valerian, hops, and black beans.

Dihydroepiandrosterone is an endogenous steroid secreted from the surface of the adrenal gland and is a precursor of testosterone and estrogen. The term phytoestrogens is descriptive and is used for non-steroidal compounds, which either exhibit estrogenic activity or are metabolized to substances with estrogenic activity. Phytoestrogens are a large family of plant-derived, non-steroidal substances that structurally or functionally resemble endogenous natural estrogens and their active metabolites. Therefore, they have significant estrogenic (agonistic/antagonistic) activity. The main groups of phytoestrogens are four: isoflavones, linoleins, coumestanes and stilbenes. They are found in more than 300 plants, especially vegetables. Phytoestrogens are structurally similar to 17β-estradiol (phenol ring) and bind to the estrogen receptors Era and Erβ. There are more than 1000 types of isoflavones. The most studied are genistein and daidzein, which have the strongest estrogenic effect. They are found in vegetables such as soybeans, chickpeas, clover, lentils and beans. Secondary soy products (milk and flour) contain lower amounts of phytoestrogens than primary products. Isoflavones are found in plants as conjugated glycosides, called glucones. This carbohydrate derivative must be broken down in the intestine, by the action of the intestinal flora, in order to produce active substances, the aglycones. The bioavailability of isoflavones depends on individual differences in intestinal flora and intestinal absorption. A difference has been found in the metabolism of phytoestrogens between men and women, with the latter metabolizing them more efficiently. Isoflavones are found in their active unconjugated form in fermented soy foods. These foods are most commonly found in Asia, where the consumption of soy products is widespread. Linoids, mainly enterolactone and enterodiol, are the most common phytoestrogens in the Western diet and are found in large amounts in flaxseed, lentils, and various fruits and vegetables. Coumestans are strong activators of estrogen receptors, but they are not included in the daily diet. They are mainly found in plant stems. Of the stilbenes, the best known is resveratrol. Its protective effect against breast cancer is the subject of research [6, 7, 8, 9].

3. Effect of phytoestrogens

Phytoestrogens can bind to estrogen receptors α and β (ERa and ER-β respectively), in the same way that selective estrogen receptor modulators (SERMs) do. Their chemical affinity for the Era and Erβ receptors may be dose-dependent but is less than that of estrogens However, some phytoestrogens show a higher affinity for Erb receptors than estrogens, which may mean that they exert their effects through different pathways.

Each phytoestrogen exhibits different estrogenic potency. For example, in the flavonoid group, genistein is stronger than biochanin A, which is stronger than daidzein. Kuiper and colleagues showed that the intensity of stimulation of transcriptional activity by the receptor varies and depends on the estrogenic potency of the phytoestrogen, which is bound. Also, phytoestrogens, as well as synthetic estrogens, show a different degree of affinity for each of the two isoforms of the estrogen receptor. In general, it appears that phytoestrogens preferentially bind to Er-β rather than Era. Phytoestrogens have limited estrogen receptor modifying ability. Studies have shown that isoflavones have agonistic and antagonistic activity but are strong ERβ and mild ERα agonists. The structural formula of the isoflavones, with the phenolic ring, is similar to that of 17β-estradiol. The similarity allows isoflavones to bind to the estrogen receptor, essentially replacing 17β-estradiol) [9, 10, 11, 12, 13, 14]. Their effect can explain the way in which phytoestrogens act protectively against breast cancer, since ERβ inhibits the growth of breast cells, while ERα promotes it. However, it is not known whether isoflavones bind to the estrogen receptor competitively at the primary estrogen binding site, or whether they have a different binding site. Furthermore, genistein has been found to bind to the active estrogen binding site in ERβ. Phytoestrogens can also promote differentiation and Studies on phytoestrogens have shown that the recruitment of co-regulatory molecules may have an important role in determining their function. In particular, isoflavones appear to selectively activate transcriptional pathways, initiated by ERβ, and in particular, transcriptional repression. The affinity shown by isoflavones for ERβ results in a change in the structure of the receptor, which thus exhibits a greater affinity for specific co-regulators than Erα, which causes inhibition of angiogenesis, cell proliferation, tyrosine kinase and topoisomera Phytoestrogens also have a dual effect on signaling pathways starting with estrogen receptors. For example, protein kinase B (Akt), whose phosphorylation normally follows ERα activation, is up-regulated by genistein and daidzein in estrogen receptor-positive breast cancer cell lines, while resveratrol has inhibited the phosphorylation of act activity. In this way, they prevent the growth of tumors. Conversely, in cell lines negative for estrogen receptor expression, resveratrol and daidzein activate act, while genistein inhibits its phosphorylation. Research into the effect of phytoestrogens on cell cycle regulators and transcription factors is contributing to the creation of synthetic substances that inhibit pathways and factors that are up-regulated by estrogen receptors. Their role is not completely known even for plants (protection from UV radiation and fungi, antioxidant activity, and many others) [9, 10, 11, 12, 13, 14].

Associated with the ERs (ERa, ΕΠβ), they have a selective modifying capacity in the final gene expression, acting on transcription factors, so that their estrogenic/antiestrogenic effect is tissue-specific and cell-specific. They are referred to as natural SERMs. They are weak estrogens, but the affinity and activation of ERβ is 100 times stronger than that of ERα. They are therefore considered to have a beneficial effect on tissues with a strong presence of Erβ (ovary, prostate, lung, CNS, bladder, gastrointestinal). In cancerous tumors, the existence of ERP is favorable for the course of the disease. They also inhibit enzymes important for the metabolism of steroids, such as 17β-H5θ5, (12 isozymes, 1,5,7 are of interest for the breast), 3β-H5D1, aromatase, sulfatase, and sulfotransferases, which convert patient estrogens and androgens, to strong estrogens with mitogenic action) [9, 10, 11, 12, 13, 14].

The above results both from in vitro cell systems, and from in vivo models of hypophysectomized, ovariectomized, (depending on the ultimate goal) experimental animals.

Like estrogens, they bind to membrane receptors, but they also exert estrogen-independent action by other mechanisms. Genistein may alter the expression of progesterone, androgen, and oxytocin receptors with unknown clinical significance. It has been reported that they induce the release of hormones from SHBG, inhibit MAPkinase, topoisomerae II etc.

They exert unwanted effects on the reproductive system, female and male. The first observations were made in sheep that developed infertility by eating subterranean clover. Also, chronic exposure of spermatozoa to high doses of genistein caused infertility, by inhibiting the acrosomal reaction and affecting their motility. The ingested plant foods are digested and the phytoestrogens they contain are converted by the intestinal bacteria into biologically active components. The amount of biologically active components absorbed varies widely, while the relative potency or affinity of phytoestrogens for estrogen receptors is 0.1–0.2% of that of estradiol.

In premenopausal women with physiologically high circulating estrogen levels, phytoestrogens compete with endogenous estrogens for binding to their respective receptors. Therefore, the net effect of phytoestrogens in premenopausal women may be antiestrogenic. Correspondingly, in postmenopausal women who have naturally high levels of natural estrogens or are receiving estrogen therapy, the net effect of phytoestrogens may also be antiestrogenic. Conversely, in postmenopausal women with low levels of circulating estrogen, the binding of phytoestrogens to estrogen receptors may result in estrogenic action of these substances. The latter, i.e. postmenopausal women with low levels of circulating estrogen and without replacement therapy for their ovarian function, have the greatest risk of vasomotor symptoms, atrophy of the vaginal epithelium and osteoporosis. This group of women is expected to benefit more from taking phytoestrogens. Recently, experimental and epidemiological studies provide convincing data on the various benefits that can come from the consumption of soy and its derivatives. For example, the isoflavones it contains seem to protect against the onset of various forms of cancer or diseases of the circulatory system, as well as against the loss of bone density. Numerous research investigations have demonstrated the impact of soy isoflavones on distinct target molecules and signaling pathways, encompassing vital cellular processes such as cell growth and differentiation, regulation of cell cycle, apoptosis, angiogenesis, cell adhesion and migration, as well as metastatic ability, along with the activity of diverse enzymes. Soy isoflavones exhibit binding affinity towards estrogen receptors α and β, thereby exerting a modulatory effect. Concurrently, these same substances appear to exert an effect independent of estrogen receptor activation [14, 15, 16].

4. Phytoestrogens and their effect on estrogen biosynthesis and excretion

Human studies of the effect of phytoestrogens on estrogen synthesis and excretion usually assess urinary levels of estrogens or steroid derivatives, as well as their metabolites. In addition, many of these studies also estimate the levels of phytoestrogens and investigate the factors influencing the values. Clinical studies have conflicting results. Lu et al. fed ten premenopausal women a high-soy diet starting from the second day of the cycle to the second day of the next cycle. Blood and urine samples were taken before and during feeding. The results showed that 17β-estradiol levels decreased by 25%, however, cycle length did not change. The Kumar et al. dietary intervention study reached similar conclusions results regarding the overall effect of phytoestrogens. The women were randomized to receive 40 mg of isoflavones or placebo per day for twelve weeks. It was found, therefore, that the values of free estradiol and estrone were reduced. Sex hormone-binding globulin (SHBG) and mean cycle length increased. In contrast, in the long-term dietary intervention study by Maskarinec and colleagues in premenopausal women, no difference in cycle length or hormone concentrations was detected. All of the above studies lead to the hypothesis that dietary intake of phytoestrogens, although important, may not be a decisive factor in breast cancer prevention by itself [14, 15, 16].

The urine phytoestrogens are metabolized by the intestinal flora into more active compounds, with the result that substances that affect the flora, potentially also affect the activity of the phytoestrogens. Administration of antibiotics has been observed to cause a sustained decrease in enterolactone levels in the gut. It appears that premenopausal women who receive long-term antibiotic therapy for urinary tract infections are at greater risk of developing breast cancer, possibly because the intestinal metabolism of phytoestrogens is disturbed. The intake of phytoestrogens, in combination with several other factors, affects the levels of estrogen derivatives in the body and their excretion. In clinical studies it is difficult to determine serum levels of phytoestrogens due to their short half-life. As most phytoestrogens are excreted in the urine, measurement of their urinary metabolites can be indicative of the phytoestrogens that dominate the diet and the main sources of intake. Some metabolites of phytoestrogens, such as enterolactone and equol, are found in urine. Urinary equol excretion was suggested as an indicator of the protective effect of phytoestrogens. Duncan et al. studied the hormonal profile of women who did or did not excrete equol in the urine and found that the first group of women had lower levels of estrone, estrone sulfate, testosterone, dihydrotestosterone, as well as higher SHBG values, regardless of dietary intake phytoestrogens. This steroid profile was found to have a protective role in breast cancer. It is noteworthy that the urinary excretion of phytoestrogens is not constant, but shows a geographical distribution. Women, living in areas with a low incidence of breast cancer, have a higher value of isoflavonoids in urine. Women who do not eat meat also have a higher concentration of isoflavonoids in their urine. However, it is unknown whether urinary enterolactone has a protective role against breast cancer or is simply indicative of a healthy hormonal profile. Certainly, the amount of phytoestrogens ingested with food is not the only factor that determines their protective effect. The levels of reproductive hormones are possibly such a factor. Phytoestrogens have been observed to stimulate the production of sex steroid hormones by liver cells. In addition, they have been found to inhibit the function of enzymes involved in the synthesis of estrogen. This, in turn, leads to low free estrogen values and reduced peripheral conversion of androgens to estrogens, which are important in estrogen development [14, 15, 16].

5. Metabolism

Individual differences in the bioavailability of the isoflavones genistein, and daidzein (most common phytoestrogens), depend on the intestinal flora. They are absorbed with soy as inactive glycosides, and are converted in the intestine into biologically active aglyconic forms, by the action of bacterial β-glucosidases. After absorption they are reconstituted in the liver mainly to glucuronic acid and less to sulfuric acid. Daidzein can be further metabolized to equol (in 30–50% of people), or to o-demethylangolensin (O-DMA) in 80–90% of the population.

A metabolite of genistein is p-ethyl phenol. The main phytoestrogens detected in the blood and urine of mammals are daidzein, genistein, equol, O-DMA. Their metabolism, mainly intestinal, and hepatic differs between children, adolescents and adults, resulting in difficulty in the interpretation of the various measurements. Phytoestrogens are polyphenolic non-steroidal plant compounds with a biological activity analogous (agonistic or antagonistic) to that of estrogens [16, 17, 18, 19, 20].

Based on their chemical composition, phytoestrogens can be divided into four main groups: isoflavonoids, flavonoids, stilbenes and lignans. Of these, soy mainly contains isoflavones, which are the best-studied substances in this category. Since phytoestrogens are structurally very similar to 17β-estradiol, they may exhibit selective estrogen receptor modifying activity. Many structurally diverse compounds, from both industry and natural sources, have been reported to have estrogenic activity. Such substances are DDT, polychlorinated biphenyls (PCBs) and diethylstilbestrol, as well as pharmaceutical estrogens, opium and ethinylestradiol. If we exclude ovarian steroids, most substances with estrogenic action are produced by plants. In addition to the substances mentioned above, there are also some that have not been sufficiently studied, such as β-resorcyclic acid lactans produced by fungi that attack nuts and classified as mycoestrogens or terpenoids and some saponins that appear to exhibit some estrogenic activity. Isoflavonoids are, as mentioned, the most studied group of phytoestrogens. The discovery of these substances was accidental and is of historical interest. In 1932, Marrian and Haslewood isolated a substance that was thought to have “contaminated” the hormone hydroxyestrine, which was found in high levels in the urine of pregnant mares (X). As the substance was found in the urine of non-pregnant mares as well as male horses, it was considered unrelated to pregnancy. Because it came from horses, it was called equoli Characteristically, the substance was isolated in the urine during the summer months, less during the autumn and not at all during the winter. Although it was not recognized at first, we later learned that this is due to the seasonal presence of isoflavones in plants [16, 17, 18, 19, 20].

Soybeans are an abundant source of isoflavones, containing approximately 2 g of isoflavonoids per kilogram of fresh weight.

However, it is important to note that the content of isoflavones in soy products can vary depending on the specific soybean variety and the processing methods employed. Consequently, different sources of soy proteins may not possess equal quantities of isoflavones, and this variability should be considered in epidemiological studies. Thus, soy proteins used in the production of meat analogs tend to have low levels of isoflavones when extracted with water, and no isoflavones if extracted with ethanol. Similarly, soybean oil does not contain any isoflavones, while soy sauce generally has minimal to negligible amounts. In addition to soy, legumes such as lentils and beans also contain isoflavones, although in much smaller quantities. Numerous types of isoflavonoids have been identified, with daidzein and genistein being the primary representatives.

These isoflavonoids are derived from their β-glycoside precursors daidzein and genistin, through their enzymatic conversion by normal flora in the gastrointestinal tract. The intestinal flora then further metabolizes daidzein to an estrogenic analog, but this biotransformation varies greatly from person to person. Despite the similarities of their biphenolic structure with estradiol, their estrogenic activity is 100–1000 times less than that of estradiol. At the same time, however, their plasma concentration can be up to 100 times higher than that of estradiol [16, 17, 18, 19, 20].

6. Phytoestrogens clinical purposes

Clinical targets of phytoestrogens include relief of vasomotor symptoms of menopause, maintenance of bone mineral density, and inhibition of breast cancer growth in retrospective studies. Due to the concern caused by the adverse effects of hormone replacement therapy, alternative treatments for the symptoms of menopause were sought, with phytoestrogens being the most important. A recent Cochrane review highlighted that the efficacy of phytoestrogens in alleviating menopausal symptoms remains inconclusive. Furthermore, a recent double-blind, prospective study involved the randomization of 60 women into two groups: one receiving a daily dosage of 60 mg of isoflavones for the duration of three months, and the other receiving a placebo. Menopausal symptoms were assessed and documented both before and after the treatment period.

Women in the phytoestrogen group experienced reductions in hot flashes and night sweats by 57% and 43% respectively Similar results were observed in another study with a small number of women and a duration of administration of phytoestrogens for six weeks.

In Europe, phytoestrogens are used clinically to treat menopausal symptoms. Recently, locust-derived prenylated flavonoids have been developed for menopausal symptoms. One such derivative is 8-prenylnaringenin, which exhibits a strong estrogenic effect, and is already administered in Belgium. Regarding the effect of phytoestrogens on bone tissue, the results of studies are conflicting. It appears that enriching the diet with isoflavones contributes to the maintenance of spinal bone density. A randomized, double-blind, controlled study compared the effects of hormone replacement therapy with genistein on bone metabolism and mineral density after one year. When the study was completed, it was found that women receiving hormone replacement therapy and those receiving genistein had a significant increase in bone mineral density at the hip, compared to women receiving a placebo. Similar data were reported by another randomized, double-blind, controlled trial comparing bone mineral density in women receiving an isoflavone extract and in women receiving a placebo [16, 17, 18, 19, 20].

Akinson et al. found that women in the isoflavone group experienced reduced bone mineral loss and bone mineral density.

Although studies on the direct effect of estrogen on breast cancer are difficult to conduct, given the long time period necessary to draw conclusions, there are studies on mammary cell proliferation and mammographic density. Short-term intake of phytoestrogen supplementation stimulates the proliferation of mammary epithelial cells. The same was observed in premenopausal women who received phytoestrogens for a long time. These histological data are also supported by the observation that women who reported even low soy consumption were more likely to present high-risk ultrasound parenchymal findings. Other studies reported similar results regarding mammographic density in women with long-term intake of phytoestrogen supplements. As shown by animal studies, the age at which a woman is exposed to phytoestrogens, as well as the duration of exposure, is potentially important in determining their potential protective effect. Key et al. conducted a prospective study involving more than 30,000 women. The women filled out a questionnaire twice over a 12-year period and were then screened for breast cancer. No relationship was found between soy consumption and the development of cancer [21, 22, 23, 24]. However, it is worth noting that the majority of women involved in the study were not adolescents. Shu et al. conducted a retrospective study focusing on women with breast cancer. Participants were asked to complete a questionnaire regarding their dietary habits during their adolescent years. The study revealed that high soy consumption during adolescence was associated with a reduced incidence of breast cancer in adulthood. This finding suggests that this factor may contribute to the observed phenomenon where women who immigrate after puberty to countries with a higher prevalence of breast cancer than their country of origin exhibit a similar breast cancer incidence rate. Nutritional supplements, particularly those containing phytoestrogens, are widely utilized for the prevention and treatment of various conditions, primarily concerning women’s health. For instance, in 2000, the consumption of such supplements reached $20 billion, with 40–55% of Americans regularly using supplements, and 24% of these supplements containing plant estrogens.

In 1975–1996, 600 articles were published on the potential benefits of phytoestrogens in cardiovascular disease, cancer (prostate, breast, colon), osteoporosis, and menopausal disorders, based on epidemiological studies that brought the above diseases to a lower rate in populations with high consumption of vegetable estrogens, mainly soy. After 2002, with the restriction of the indications of hormone replacement therapy (HRT) exclusively to severe vasomotor symptoms of menopause, the role of phytoestrogens as an alternative proposal to HRT is very important [21, 22, 23, 24].

7. Cardiovascular disease

Genistein, 54 mg daily improved glycemic and vascular indices in normoinsulinemic, and insulin sensitivity in hyperinsulinemic women. In a double-blind, randomized controlled trial of 22 women, mean age 58 years, a comparison of 60 mg raloxifene and 55 mg phytoestrogens had no effect on humeral expansion. Of the components of the metabolic syndrome, with the administration of various soy foods, only hypertension appears to be associated with mental disorders, while any protection in CHD is due, not to protein, but to other components contained in soybeans (fiber, polyunsaturated fat, vitamins) [24, 25, 26].

8. Osteoporosis

In in vitro tests they stimulate osteoblasts and suppress osteoclasts through IL-6, OPG, RANKL. In vivo models of adult ovariectomized mice have been developed to study their effect on bone metabolism. In histomorphometric studies in mice, dietary administration does not protect bone. Ipriflavone, a synthetic isoflavone, did not affect BMD and vertebral fractures in 475 postmenopausal women at a dose of 600 mg for 4 years. Other authors observed with the same formulation, an improvement in osteoporosis indicators, but there is no clinical indication for prevention of osteopenia, and reduction of the risk of fractures [25, 26, 27, 28, 29].

In Asia, the incidence of fractures due to osteoporosis is lower compared to that seen in Western countries. This fact can be due to many reasons such as some related to anatomical differences, but a main reason could be the high intake of phytoestrogens from foods. Asian populations consume 10–20 times more soy, a major source of isoflavones, than populations in Western societies. High dietary intake and high urinary excretion of isoflavones has been associated with high bone mineral density in Chinese, Japanese, and Korean postmenopausal women [25, 26, 27, 28, 29].

Small clinical studies in humans have shown the protective effect of phytoestrogens on tonic metabolism. Soy isoflavones, genistein and daidzein, prevent postmenopausal bone loss in the lumbar fate of the spine. A high dose of isoflavones, about 90 mg daily, had a favorable effect on bone density, as observed in a study of elderly postmenopausal women.

In a randomized, double-blind, one-year study, researchers evaluated the effect of genistein on ninety healthy postmenopausal women. These women were given hormone replacement therapy with estrogen and progesterone or genistein at a dose of 54 mg per day or placebo. Bone mineral density was assessed and bone metabolism products were measured in blood and urine, and their results showed that genistein and hormone replacement therapy reduced bone loss about equally.

Assessments of bone metabolism have shown that genistein enhances bone formation and simultaneously decreases bone resorption, whereas hormone replacement therapy appears to only decrease bone resorption.

The effect of phytoestrogens on bone metabolism in fifty-five postmenopausal women who had survived breast cancer was studied in a prospective controlled study. The women received 114 mg of isoflavones daily or a placebo for 3 months [25, 26, 27, 28, 29].

Bone resorption, as reflected in urinary pyridinoline and deoxypyridinoline excretion, was significantly reduced in the isoflavone-treated group, while bone formation indices were not affected by this treatment regimen. Indirect evidence for the potential benefits of phytoestrogens on bone metabolism also comes from studies with ipriflavone, an isoflavone derivative. At daily doses ranging from 200 to 600 mg per day, this synthetic, non-hormonal drug has been shown to be effective in increasing bone mass and preventing bone loss.

Impressive data from multiple studies in bone cell cultures as well as experimental models of postmenopausal osteoporosis in rats support the significant protective effect of the soy isoflavones genistein and daidzein on bone. Transferring these research data into clinical practice has been a challenge. Human studies have shown favorable but mixed results. Most clinical studies are of short duration and in a relatively small number of subjects, making it difficult to observe significant and detailed changes in bone. At the same time, the level of intake of soy protein and isoflavones varies in these studies, and the optimal dose of intake, so that there is a protective effect on bones, has not yet been determined. The clinical studies that have been so far can be distinguished into those that have determined biochemical evidence of reduced bone turnover by assessing markers of osteoblast and osteoclast activity and those that have examined changes in bone mineral density.

The overall results indicate that diets rich in phytoestrogens have a long-term protective effect on bone. The magnitude of their effect and their precise mechanisms of action are currently elusive or merely conjectural.

It has been known for a long time that women in certain peoples of the Far East, such as the Chinese and Japanese, are affected at much lower rates by certain diseases such as osteoporosis, atherosclerosis, but also by certain cancers such as breast and ovarian.

Also, it was shown in epidemiological studies that these women complain less about symptoms and disorders that appear during menopause, than women in the West. In the effort to detect the protective factors responsible for these differences, great importance was given to diet. After excluding some factors that seem to be associated with the increased incidence of stomach cancer in Japan, such as preserved foods and especially pastes (which contain particularly high levels of salt, nitrites and nitrates), soybeans, which are used in various ways, were evaluated in the preparation of Japanese and Chinese cuisine. In addition to proteins and lipids of high nutritional value, soy also contains some substances with structural similarities to estrogen [25, 26, 27, 28, 29].

Recent epidemiological and experimental studies report that diets rich in phytoestrogens may have a protective effect on estrogen-dependent conditions such as menopausal symptoms and estrogen-dependent diseases such as breast cancer, osteoporosis, and cardiovascular disease.

9. Breast cancer

The treatment of hot flashes in women with Ca mastitis is a particularly difficult clinical problem, which will increase over time, for two main reasons. (1) The increase in survival, (2) the increase in the number of very young affected women, in whom the vasomotor effects are more intense, with consequent impact on the quality of life. In in vitro, preclinical and clinical studies the results are highly contradictory. The purity of the phytoestrogen form increases the stimulatory estrogenic effect and reverses the effect of tamoxifen. In women with aromatase inhibitors, what is the action of phytoestrogens? In America they are not recommended to consume large amounts, as in Asia, but there is no concern about the usual diets [29, 30, 31, 32].

A recent study showed a strong inhibitory effect on 17β-H5D1, which converts E1 to E2, 10 flavonoids, as well as intermediate products of their biosynthesis, while none had a proliferative effect on breast cancer cells They seem to protect only women who are exposed from an early age, from fetal possibly, in reproductive life studies come to conflicting conclusions, while for menopause there are also insufficient results for their potentially harmful effect. Of interest is a prospective study in Japan, which showed that Genistein, Daidzein, and soy have a positive dose-dependent relationship with the increase in hepatocellular carcinoma (HCC) in women, particularly those with hepatitis, while they had no effect in men. Since HCC occurs at higher rates in the male population, so endogenous estrogens may have a prophylactic role, the herbal study showed a different effect in the two sexes.

10. Mental functions

In in vitro and in vivo studies there is a neuroprotective effect through selective activation of EPβ. A study of young women given a 1-week diet rich in phytoestrogens showed no effect on various mental skills. Taking 160 mg/day of total isoflavones, in the form of powder in drinks, for 12 weeks significantly improved hot flashes, mood, physical condition, but did not affect lipids and cognitive functions at all. Some authors argue that they have an estrogen-like beneficial effect on memory if administered peri- or very early postmenopausal Another study showed that isoflavones by mechanisms independent of estrogen, had a beneficial effect in young women. Many aloe vera skin care products contain anthraquinones, while breast enlargement products 8-prenylnaringenin etc.

Their anti-inflammatory, immunosuppressive-immunostimulatory property also raises many questions. It has been reported to protect the skin (red clover) from the immunosuppression of UV radiation, through their antioxidant and anti-inflammatory action.

Genistein in vitro and in vivo has an antiviral effect on DNA and RNA viruses that infect humans and animals. It also acts on the host cell, and on the attachment, entry, replication of the virus, through inhibition of tyrosine kinases and topoisomerase II. Pharmacological and toxicological in vitro studies have shown apoptotic and toxic effects of some phytoestrogens in some cell systems. They suggest that it is important to pay attention to the consumption of concentrated amounts of phytoestrogens in the form of phytohormone supplements, although dose-dependent studies are needed to draw conclusions. In contrast there is no need for concern regarding the intake of phytoestrogens from a regular diet [29, 30, 31, 32, 33, 34].

11. SERMS (selective estrogen receptor modulator)

Another class of drugs recommended for ΗΡΤ are SERMS (selective estrogen receptor modifiers) that simultaneously display an agonistic and antagonistic effect of estrogen depending on the tissue. In particular, in bone tissue, the cardiovascular system, lipid metabolism, they have an estrogenic effect, which is different from that of 17β estradiol and tamoxifen SERMS exhibit endometrial estrogenic activity, inhibit breast estrogen receptor activity, and antagonize estrogen-dependent proliferation of MCF-7 cells in breast tumors.

In addition, they do not show mitotic activity in the breast, endometrium, are administered without progestogen in an existing uterus and have a satisfactory effect regarding the prevention of osteoporosis particularly noteworthy is the lack of influence on ovarian function and hypothalamic pituitary axis disadvantages include unsatisfactory treatment of climacteric symptoms and are therefore a treatment of choice for the prevention of osteoporosis in cases of breast cancer and in vaginal bleeding occurring in conventional therapy The mentioned phodioestrogens are components of students with a source of origin mainly soy. In cases of contraindications to HRT, it is suggested to enrich the diet with foods rich in phodioestrogens and lead to a remission of vasomotor symptoms, protection of the cardiovascular system, but they are less effective in osteoporosis and atrophy of the genitourinary system.

The SERMS category includes substances that act as estrogenic agonists or antagonists depending on the tissue. This category includes tamoxifen (anti-estrogenic effect on the massive mammary gland, estrogenic effect on the endometrium), Clomiphene used in cases of a afollicular infertility affects the pituitary gland with an anti-estrogenic effect in women of reproductive age, however, its action in the pituitary gland of postmenopausal women is estrogenic.

SERMS act selectively on estrogen receptors either as agonists or antagonists in a target gene and have beneficial effects of estrogen on target tissues avoiding negative off-target effects. According to recent data they act as agonists with estrogen receptors in bone tissue cardiovascular system competitively in the breast.

There are four SERMS formulations approved for clinical use.

The three formulations belong to the triphenylethylene family and are as follows:

1. Clomiphene

2. Tamoxifen

3. Toremifene

Raloxifene belongs to the benzothiphene family (second generation SERMS), it is the main representative of SERMS, it comes from a modification of the molecular structure of clomiphene citrate, tamoxifen and is a selective modifier of estrogen receptors.

The indication for raloxifene administration is in women at increased risk for breast cancer as an alternative treatment for HRT. The recommended dosage is 60–120 mg, the duration of treatment is 4 years and a reduction in vertebral and not vertebral fracture is observed. Indifferent from applications-modus: orally or vaginally [27, 28, 29, 30, 31, 32, 33, 34, 35, 36].

The substances contained in these preparations act as antagonists in the female reproductive system (endometrium, breast) where α-estrogen receptors prevail and have an agonistic effect on the skeleton (β estrogen receptors), lipoprotein profile.

In particular, raloxifene has an indication for the prevention of osteoporosis due to the certified manifestation of estrogenic effects on bones, increasing bone density and anti-estrogenic effects on the breasts and the endometrium.

It acts competitively with the intake of calcium and vitamin D in the bones, it has a cardioprotective effect by inhibiting the oxidation of LDL, while a 1/10,000 thromboembolic event and slight side effects, seasickness myalgia, are reported. Raloxifene influences the pituitary gland and the release of gonadotropins in addition to its favorable effects in the prevention or treatment of osteoporosis. In experimental animal studies, raloxifene prevented the morning fall in LH levels induced by estradiol, while it did not affect the evening rise in the levels of the mentioned hormones.

The anti-estrogenic effect of raloxifene on the gonadotropic cells of the anterior pituitary gland was certified in these studies. Also, in other experimental studies the anti-estrogenic effect of raloxifene on the hypothalamus was certified. of the basal secretion of FSH and LH in postmenopausal women and exerts an agonistic or antagonistic effect on the estrogen receptors depending on the tissue.

The new selective estrogen receptor modulators include Bazedoxifene, Lasoxifene [27, 28, 29, 30, 31, 32, 33, 34, 35, 36].

12. Vascular menopauseal symptoms

In 2007, results were published in which the clinical significance of Trifolium pretense (red clover) in improving hot flashes was questionable. In 2008 in a total of 1112 peri- and post-menopausal women, from various countries, also uncertain result, after taking Black cohosh (Cimicifuga racemosa), Cimicifuga or Botryoidus or Coriander. Their usefulness in cases of mild-moderate symptoms, at a relatively young age, is not in doubt. A 2009 meta-analysis on the side effects of phytoestrogens reported gastrointestinal discomfort (abdominal pain), myalgia and insomnia at significantly high levels, while there was no thrombosis, stroke, vaginal bleeding, myocardial infarctions, endometrial hyperplasia, or breast cancer.

In January 2009 the Cochrane Database of Systematic Reviews published results of 30 studies in peri- and postmenopausal women who received high doses of soy, soy extract, red clover extract (Promensil), and other phytoestrogens for at least 12 weeks. Of the 30 studies, few met the criteria for inclusion in a meta-analysis. In these, no significant reduction of vasomotor symptoms was found compared to placebo, which, however, in several studies, had a marked improvement in both hot flashes and night sweats. In the remaining, low-quality studies, they observed a small reduction in discomfort always compared to a placebo.

A Mayo Clinic pilot study was considered encouraging, in which 30 women received 40 g of ground flaxseed daily for 6 weeks, and recorded a significant reduction (>50%) in their hot flashes score. However, a longer study in terms of duration and number of women is needed for definitive conclusions. In the above study 50% experienced mild abdominal distention, 30% mild diarrhea, and 20% discontinued due to side effects.

The authors do not consider that there is sufficient evidence to recommend phytoestrogens in the treatment of menopausal symptoms. Hyperplasia of the endometrium, for administration up to 2 years was not observed, but intake of soy 150 mg daily, for 5 years caused hyperplasia. With what is known to date, long-term safety for the body as a whole has not been established [27, 28, 29, 30, 31, 32].

It is clear that the variety and contradiction of the above is not only due to the small number of good quality studies (control group, duration, small participation, etc.), but also to inherent peculiarities, such as (1) new phytoestrogens are constantly being isolated, (2) nomenclature problems, (3) individual differences in their intestinal and hepatic metabolism, (4) different action depending on the endogenous estrogenic environment, (5) difference in action depending on dose, route of administration, duration of exposure, and age (from fetal to postmenopausal), (6) confusion between the substance and the food containing it, (7) the method of extraction from the plants probably affects their action and (8) genetic polymorphism.

The idea that “natural” is safe and beneficial is not accepted in every case. Phytoestrogens, in any form and concentration, are not indicated for the treatment of menopausal vasomotor symptoms, due to insufficient medically documented knowledge about their effectiveness. Bearing in mind, the potentially harmful effects on the body, during their long-term administration, the decision should be individualized, and in the case of insistence on the alternative route, it is necessary to explain their action, the recommendation for short-term use, and the same control as in classic HRT [27, 28, 29, 30, 31, 32, 33, 34, 35, 36].

Phytoestrogens are a modern alternative, but derived from a long pharmaceutical tradition, for the treatment of osteoporosis and at the same time a holistic proposal for the treatment of the symptoms and problems of menopause. Phytoestrogens are substances present in food that have a modifying effect on estrogen receptors and may have partial estrogenic and anti-estrogenic effects [32, 37, 38, 39, 40, 41, 42].

Multiple epidemiological data and experimental findings from in vivo animal studies support the protective effect of phytoestrogens on bone loss, in vitro experiments argue for their action on bone, specifically on the osteoclast and osteoblast, while some other data show that they improve the absorption of calcium in the intestine and thus may improve bone density [27, 28, 29, 30, 31, 32, 33, 34, 35, 36].

Additionally, human clinical studies of phytoestrogens show that they may protect against bone loss seen during and after menopause and with age. In conclusion, as shown by the multiple research data of recent years, phytoestrogens may improve bone mass by acting diversely on bone metabolism, thus constituting a new alternative treatment for osteoporosis.

Phytoestrogens are substances present in food that may have an estrogenic effect. Phytoestrogens are divided into isoflavones, lignans and coumestans. Isoflavones are converted by intestinal bacteria into genistein and daidzein, while lignans are converted into enterolactone and enterodiol. A variety of foods contain sufficient amounts of the various phytoestrogens, such as soy and flaxseed products, which are particularly rich sources of isoflavones and lignans respectively.

Today, phytoestrogens seem to be a new alternative, but with deep roots in past centuries, a solution for dealing with osteoporosis as well as the symptoms and problems that accompany the loss of ovarian function, i.e. menopause. Epidemiological, experimental and clinical data support their protective role in osteoporosis.

13. Biological impacts of phytoestrogens

The potential of numerous isoflavonoids to interact with estrogenic receptors has been extensively examined. Research has revealed that coumestrol exhibits the strongest binding to estrogenic receptors among the isoflavonoids, comparable to that of 17β-estradiol, affecting both ERα and EIF receptors. Conversely, genistein, daidzein, and equol exhibit a higher inclination to bind with ECβ receptors rather than ERα receptors. Isoflavones are often present in higher concentrations in the body compared to endogenous estrogens. However, the methylation or glycosylation of isoflavones generally diminishes their chemical affinity for estrogen receptors.

Certain isoflavonoids can hinder key enzymes involved in the synthesis of estrogens and androgens, such as aromatase, 5α-hydroxylase, and 17-OH-dehydrogenase. This explains the observed decrease in the occurrence of hormone-secreting cancers like breast and prostate cancer. Moreover, additional effects of isoflavonoids have been documented, including the inhibition of tyrosine kinase synthesis, DNA topoisomerase I and II, and their antiangiogenic and antioxidant properties. Therefore, apart from their selective estrogen receptor modulator (SERMs) properties, isoflavonoids show potential in the prevention and treatment of various types of cancer, at least in experimental models.

Replacement therapy is administered to postmenopausal women to prevent menopausal symptoms, osteoporosis, and cardiovascular disease. Despite these benefits, after the WHI study, there are concerns about the development of various cancers in these women. Today, many studies are investigating the possibility of using phytoestrogens as an alternative replacement therapy. An important work by Potter et al., showed an inhibition of bone loss if the diet contains for six months 90 mg/day of isoflavonoids. The dose, however, was quite large and as noted in a study by Scambia et al., a daily dose should not exceed 50–60 mg, in order to avoid adverse effects. Furthermore, ipriflavone, which is an alternative replacement therapy for pre-existing low bone density or menopausal osteoporosis, also showed some results in osteoporosis. Iproflavone is a synthetic isoflavone derivative of daidzein that has been approved in several countries for the treatment of osteoporosis. It does not appear to act through a direct effect on estrogen receptors, so it could only be classified as a phytoestrogen in the broadest sense. However, a percentage of 10% after its intake by the body turns back into daidzein. However, a large multicenter study did not show its effectiveness and linked it to several side effects [32, 38, 39, 40, 41, 42, 43, 44].

There are enough data from the use of isoflavonoids in hot flashes during menopause, but without being able to unequivocally support their prescription. In a double-blind study, 177 menopausal women were randomized to receive either 50 mg/day of soy isoflavonoids or placebo. Women in the placebo group woke up an average of 1.89 times during the night due to night sweats and hot flashes, while women taking the soy isoflavonoids woke up 1.52 times, an improvement of 12.4%.

Also important was the reduction in the intensity of the vasomotor phenomenon, as assessed by the women. Various researchers have of course noted the logical observation that the reduction by 12.4% means that if a woman had ten episodes of hot flashes, with the drug the episodes would now be nine, an observation that underlines that statistical significance does not always go hand in hand with clinical effectiveness.

In a more recent work, 75 menopausal women with at least seven hot flashes/day were randomized to receive soy isoflavonoids or placebo for 16 weeks. The percentage of women reporting at least a 50% reduction in hot flashes was 65.8% in the isoflavonoid group and 34.2% in the placebo group, a difference that was statistically highly significant (p < 0.005). However, it must be emphasized that in this study as well as in others, no change was observed in other menopausal symptoms [32, 36, 37, 38, 39, 40, 41, 42, 43, 44].

On the other hand, in a very recent double-blind study of 72 women who were randomized to receive soy capsules or a placebo, no statistically significant difference was observed in the relief of menopausal symptoms or overall quality of life. Finally, in the recent position of the North American Menopause Society, it is noted that the studies published to date can neither support nor reject the administration of isoflavone supplements or the consumption of foods containing soy. Finally, however, for the relief of mild vasomotor symptoms, he recommends the administration of isoflavones in combination with lifestyle changes as an initial treatment before the administration of drugs [44, 45, 46, 47, 48, 49, 50].

14. Possible adverse effects

In general, both soy contained in foods and isoflavones contained in preparations are well tolerated. However, due to the relatively limited and often conflicting data from in vitro and experimental animal studies, a definitive safety assessment for isoflavonoid intake cannot be made. Moderate intake of isoflavonoids appears to be safe for the majority of people, whereas long-term consumption of soy products and isoflavone-containing formulations is currently recommended for women with a history of breast cancer [46, 47, 48, 49, 50].

15. Conclusions

The lifestyle and eating habits of Asian pigs are very different compared to the West, so even differences in the occurrence of diseases or menopausal disorders cannot be attributed to the consumption of soy and its products alone. Given how the doses of commercial preparations, phytoestrogens have not yet been clarified in large studies and the possible—long-term—side effects are generally unknown, one cannot unreservedly recommend their administration. However, the evidence from the often conflicting studies is generally encouraging and certainly indicates the need for further investigation. Regarding their use in menopausal symptoms, most researchers tend to agree that the use of substances such as soy phytoestrogens could be used as a first-line treatment for mild symptoms not associated with sleep or daytime activity disturbances, along with lifestyle changes.