Soy beans and their derivative products contain naturally occurring compounds called isoflavones. The isoflavones, occurring predominantly as daidzein and genistein, are not in actual sense estrogens, and, thus, they do not increase estrogen levels in blood when diets rich in them are taken. However, they have been noted to affect estrogen metabolism. Also known sometimes as phytoestrogens, because of producing weak-estrogen like effects in the body, isoflavones usually bind to estrogen receptor proteins, which in turn interact with one’s genetic materials in the cell. In this way, isflavones would be mimicking some of the physiological effects of the body estrogens. Biological effects of isoflavones have not been clear. There have been confusions regarding effects of soy on estrogen, particularly if it produces estrogen-like activities, including men feminization (Hark & Morrison, 2009). Although some studies have indicated that indeed soy could have estrogen like effects in women at certain stages of their lives, others have noted that it does not significantly affect estrogen, and hence its estrogen-like effects are minor. However, there seem to be a consensus that eating soy diet moderately has no significant effects on estrogen levels and estrogen-like effects (Dinsdale & Ward, 2010). This study reviews several literatures concerning effects of soy diets on estrogen. In this regard, there will be a general analysis of the functioning of the soy isoflavone compound and how it affects the estrogen. The study will then embark on discussing effects of the soy diet on estrogen. Variability in findings among studies will be analyzed before the conclusion is made.
Soy diets contain phytoestrogens which are compounds in plants that are chemically similar to estrogen in animals. When one consumes the soy products, it is believed that they will enhance estrogen-like activities in the body (Hark & Morrison, 2009). Normally, estrogen is thought to control female reproduction activities and other feminine aspects such as skin tone, metabolism, bone and blood vessel health, cholesterol levels, sexual desires and fluid balance (Hark & Morrison, 2009; Beaton et al., 2010). Some studies in East Asia have indicated that soy consumptions have feminized some men, in that they have been declining in masculine aspects and developing feminine characteristics mentioned above. Therefore, to ascertain whether soy consumption has effects on estrogen, one has to manifest the above aforementioned characteristics (Hark & Morrison, 2009).
Specifically, soy isoflavone activates the body’s estrogen receptors. The estrogen receptor, which is a protein that detects the presence of estrogen, carries out estrogen-like effects including changes in gene expression. Studies have noted that the isoflavone usually does it weakly compared to estrogen (Nagata et al. 2010). In case of low or no estrogen, the isoflavone would weakly activate the estrogen receptor to mitigate the effects of low or no estrogen. In case the body has abundant estrogen, the isoflavone reduce the effect of the estrogen, limiting the effects of estrogen of producing more feminine effects in the body. Given this way, estrogen plays the role of controlling levels of estrogen effect through feedback mechanism (Hark & Morrison, 2009).
Although there are some instances of estrogen effect of soy in men, majority of studies have found no or insignificant estrogenic effect of soy in men. The Beaton et al. (2010) study found that consumption of high or low content levels of isoflavones did not significantly alter semen quality in men. Kraemer et al. (2013) have also reiterated the Beaton et al. (2010)’s study. Their study being done on a sample of ten selected exercise men, with a balanced placebo design, found no significant effects of soy intake on muscle build-ups due to increased estrogen production. Messina (2010), with a data cross-referencing and Medline literature review, found that isoflavones did not exert any feminizing effects in men. However, Nagata et al. (2010) has contradicted this view by finding that consumption of highly conctrated soy diet could modify estrogen concentration in Japanese men. The study by Kurzer (2012) indicated that in some cases, consumption of soya could influence semen quality due to increase or decrease in estrogen quality. Therefore, although the studies can be conflicting, majority of them indicate that estrogen effect of soy in men is not significant in a large population.
There has been no clear consensus on whether soy consumption can influence body natural estrogen and its effect or not in women. In Kurzer (2012)’s control studies, it was found in about seven studies that soy diet intake could control menstrual cycle in women. By giving women estrogen-like boosts, at the time when estrogen level is dwindling, Phares (2014) found that isoflavone cools the hot flashes due to increased activation of the body’s estrogen receptors. This is agreed with Mangels et al. (2011), who found that estrogen could reduce some of the menopausal problems. However, Levis et al. (2011) contradict them by noting that that intake of soy tablets could not alter menopausal symptoms. Moreover, Maskarinec et al. (2011) found that amounts of soy foods intake among Asians women could not significantly alter estrogen levels in serum and NAF. Evidently, there is no single consensus among the studies about if there is estrogen effect of soy in women.
In the studies, one can note that there is still unclear consensus on the estrogen effect of soy in both men and women. This view was shared by Dinsdale and Ward (2010) who indicated that findings of previous studies on biological effects of soy in humans had been controversial. However, most studies in men indicate no or insignificant estrogenic effect of soy (Kurzer, 2012). In women, it can be noted that there are significant result in those that are fighting menopausal problems. It is because, in case of low or no estrogen, isoflavones can weakly activate estrogen receptors to mitigate effects of low or no estrogen. As a result, some of the menopausal problems will be mitigated (Phares, 2014). Therefore, benefits of soya diets in mitigating some reproductive problems are evident in women.
As a conclusion, soy effect on estrogen in men is not common and not significant. In females, significant effect can be witnessed. However, more researches need to be done on why men in South East Asia are more susceptible to feminization by estrogen effect of soy. Moreover, studies are needed on menopausal requirements for soy to be effective in activation of estrogen receptor. The studies are pertinent in that they add on current evidence-based observations about effects and benefits of estrogen effect of soy in both men and women.
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