Soy May Impact Male Reproductive Disorders

This review of various studies was done to establish the role of soy-based foods on the reproductive function and infertility rates in males and animals. Soy foods contain certain compounds that could disrupt various reproductive hormones, thereby leading to infertility. A few studies have indicated that the compounds in soy food could lead to low sperm counts, reduced sperm maturation and a reduction in reproductive hormones; however, there are also several detailed studies that disprove the fact. Further investigation is mandatory but the authors suggest the avoidance of soy-based foods being fed to infants.

The incidence of male reproductive disorders has doubled in North America, between the 1970s and 1990s, and is still on the rise. It is likely that environmental factors such as fungicides, pesticides and certain plastics play a key role in this. Researchers have also stated that various chemicals used in day to day life have a direct role on this process. However, the role of natural compounds like phyto-estrogens in soy-based foods has been overlooked. These phyto-estrogens are inactive in soy, but they are activated by certain intestinal enzymes. Although these soy-based foods have been associated with a reduced incidence of breast and prostate cancers, they have been linked to reproductive disorders and infertility. Soy-foods are used in abundance as soy-based formulae for infants, sometimes even substituting breast milk. Since most results on studies based on soy-based foods and infertility are inconsistent, this review was performed to assess and interpret data to draw a final conclusion.

* Various research articles on soy-based food and reproductive function were referred to and the results were analyzed.
* The results were compared and discussed with respect to key topics on reproductive function. Animal and human based studies were separately discussed. Studies, which included the combined effects of both soy-based and environmental-based hormonal disruptors, were also discussed.
* The shortcomings and positive aspect of related studies were grouped and listed.

* Newborn male rats, when exposed to a component in soy products showed a reduction in testis size and serum testosterone levels on lactation. A lifelong additive exposure to this soy component (gestation, lactation and adulthood) increases the effect. The soy component, in combination with endocrine disruptors like BPA (a chemical used to make certain plastics and often found in the lining of cans) and other environmental pollutants increased the adverse effects on sperm too.
* A lifetime of exposure to soy could contribute to lower fertility levels.
* Various studies reviewed dietary soy intervention on male reproductive hormones
* Studies carried out on male humans showed that there was an inverse connection between soy product intake and key male hormone concentration in men, though this relationship was borderline. Isoflavone, however, did affect the capacitation of sperm (their ability to mature and enter a female) and caused significant sperm damage.

Shortcomings/Next steps
Though many studies have been done, comparing them isn’t feasible, owing to the use of different soy-formulations, different routes of intake and different exposure times, in each study.  Most studies weighed the reproductive organs in animal studies rather than assess the reproductive function. In another study, human subjects were chosen from infertility clinics, and they could have had initial reproductive issues. With totally contrasting results obtained from various studies, more research has to be done regarding the influence of phyto-estrogens on the male reproductive system.

From studies done, it can be assumed that environmental factors and compounds present in soy-based foods could increase the occurrence of male reproductive disorders. However, there are other studies on the same issue, stating the insignificance of soy-based foods. Thus, considering the lack of consistency in studies on both humans and animals, more research needs to be done. As these discrepancies have risen due to improper designs of the study or issues with choosing the subjects or inadequacies in the tests performed, standardization of these experiments would be necessary. Nonetheless, it would be better to avoid feeding infants soy-based foods.

For More Information:
Soy, Phyto-Oestrogens and Male Reproductive Function
Publication Journal: The International Journal of Andrology, November 2009
By Christopher R. Cederroth; Jacques Auger; University of Geneva Medical School, Geneva, Switzerland and the Cochin Hospital, Paris, France

*FYI Living Lab Reports Are Summaries of the Original Research.


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