The Effects of Soy Isoflavones on the Uterus and Urethra - research article

This study looked at the effects of soy isoflavones on the uterus and urethra of rats whose ovaries were removed. Many women now usephytoestrogens to help relieve urorgenital symptoms associated with lower oestrogen levels after menopause.

The authors state that Phytoestrogens are non-steroidal compounds naturally occurring in plants, which contain a phenolic group similar to estrogens. They have been studied in more depth since the 1940s, when it was observed that Australian sheep fed red clover had changes in fertility. Isoflavones, the most studied and the most common phytoestrogens in the human diet, are found mainly in soy-based products. The main isoflavone compounds are genistein, daidzein, biochanin A and formononetin. Genistein is the most abundant and active soy phytoestrogen. Isoflavones have the highest estrogenic activity among the phytoestrogens. The estimated intake ofisoflavones in Asian countries such as China is 20–80 mg/day. In American post-menopausal women, it is under 1 mg/day. 

Several effects have been attributed to isoflavones in post-menopausal women, including improvement in hot flushes, cognitive function, prevention of loss of bone mass, improvement in lipid profile, endothelial function and urinary incontinence, all without an increase in the incidence of certain types of cancer, such as breast cancer, or even as a possible protective factor for some types of cancer, related or not to the use of hormones. Urinary incontinence affects approximately 63.5% of post-menopausal women and lower oestrogen may be involved in the origin or worsening of this condition.

These authors evaluated different doses of genistein, and noticed an effect in the prevention of bone mass loss in rats with removed ovaries. Their experiment, demonstrated an increase in uterine weight in castrated female rats allowing the authors to conclude that the dose ofisoflavone extract used was capable of promoting oestrogenic activity, so an effect on the urethra may also be assessed.

This is an initial study on the effects of isoflavones on the lower urinary tract, suggesting a promising role in the improvement of urinary symptoms resulting from menopause; however, more studies are necessary to reach definitive conclusions.

  Santos E, Dutra Sampaio M, Roberto Cecon P, Simões M, Ferreira Sartori M and Castello Girão M. Effects of soy isoflavones on the uterus and urethra of ovariectomized rats. IUJ 2010. Vol 21;1:111.116