Effects of soy phytoestrogens on the prostate

Abstract

Worldwide disparities exist between geographic regions with regard to prostate cancer incidence and mortality. Countries in East Asia have lower rates of prostate cancer compared with Western countries such as Canada and the US. Some suggest that dietary differences between the two geographic regions, particularly the higher amount of phytoestrogens consumed in East Asia, is responsible for the difference in prostate cancer incidence. The mechanism of action of the soy isoflavones is incompletely understood, but in regards to prostate carcinogenesis likely involves estrogenic effects, cell cycle inhibition, anti-angiogenesis and induction of apoptosis. Recent clinical studies have provided mixed results with regard to a clear association between prostate cancer and soy consumption. Further studies are needed to understand more clearly the relationship between soy consumption and prostatic diseases.

Plasma phyto-oestrogens and prostate cancer in the European Prospective Investigation into Cancer and Nutrition

“…Our finding of a possible protective association of genistein with prostate cancer risk is consistent with the experimental data from in vivo and in vitro studies (Bingham et al, 1998;Bylund et al, 2000;Goetzel et al, 2007). This association may be mediated by oestrogenic and/or a number of anti-carcinogenic properties, although the biological effects of exposure to phyto-oestrogens in humans remain uncertain (Bingham et al, 1998;Magee and Rowland, 2004;McCann et al, 2005;McCormick et al, 2007).…”

“…International comparisons, small randomised trials and experimental data from animal models and cell lines suggest a possible protective association between dietary phyto-oestrogens, including isoflavones and lignans, and the development of prostate cancer (Goetzel et al, 2007;Perabo et al, 2008). Results from prospective epidemiological studies of dietary phyto-oestrogen intake and prostate cancer risk generally support this hypothesis (Severson et al, 1989;Jacobsen et al, 1998;Allen et al, 2004;Nomura et al, 2004;Low et al, 2006;Kurahashi et al, 2007), previous studies of circulating concentrations of lignans have been inconclusive (Stattin et al, 2002(Stattin et al, , 2004Kilkkinen et al, 2003;Ward et al, 2008), and there have been no large-scale prospective investigations of circulating concentrations of isoflavones in relation to prostate cancer risk.…”

In touch with your feminine side: how oestrogen metabolism impacts prostate cancer

“…Additionally, it has been observed that such a Western diet is more likely to cause men diagnosed with prostate cancer to die from the disease when compared with a diet rich in fruits, vegetables and whole grain cereals (Yang et al 2014). Supporting this, it has been widely speculated that dietary oestrogenic compounds from plant sources, termed phytoestrogens, are protective against prostate cancer and are the reason behind lower incidence rates in East Asia, where per capita consumption of phytoestrogen-rich foods, such as soya beans, is considerably higher than the Western world (Strom et al 1999, Adlercreutz et al 2000, Goetzl et al 2007. It is possible that phytoestrogens reduce the risk of prostate cancer through multiple mechanisms.…”

“…However, normal non-cancerous PrEC prostate epithelial cells were not affected as harshly showing 90% cell viability compared with circa 20% in cancerous cell lines at concentrations of 30 µM (Sarveswaran et al 2012). While in vitro evidence argues that phytoestrogens are protective against prostate cancer, clinical trials looking at the relationship between consumption of dietary phytoestrogens and progression of prostate cancer have been inconclusive (Goetzl et al 2007). One doubleblind randomised control trial in which 81 healthy men were either given a soy protein drink with high isoflavone concentration (83 mg/day) or a drink with low isoflavone concentration (3 mg/day) showed no significant difference in PSA over 12 months (Adams et al 2004).…”

“…This reduction in androgen is thought to be important in the reduction of risk. In addition to chelation of free testosterone via SHBG, phytoestrogens have a negative feedback effect on the HPG axis directly leading to reduced secretion of luteinising hormone and consequently reduced stimulation of androgen and oestrogen syntheses (Goetzl et al 2007).…”