-phytoestrogens cause lower testosterone levels and lower Zinc levels
-most common dietary source of phytoestrogens is soy and soy products
-beware of soy-derived lecithin in bodybuilding supplements
Phytoestrogens are non-hormonal substances derived from plants that resemble the human hormone estradiol and other estrogenic hormones.
While higher estrogenic profile can be beneficial for female athletes (especially in the 50+ age group) it is usually perceived as harmful in male trainees (and in men generally).
There is a large number of scientific studies showing that phytoestrogens are lowering the testosterone levels in males.
The main dietary source of phytoestrogens is soy and soy products including the soy-derived lecithin.
Strangely, most performance-enhancing sport supplements that are supposed to promote anabolic effects within the muscle include soy-derived lecithin.
True, the overall amounts of phytoestrogens in such products are not high but considering that most processed food also contains some soy products, the numbers add up.
Along with lowering the testosterone, phytoestrogens cause another serious side-effect: they lower the Zinc levels in blood by promoting Zinc deposits in bones.
Zinc participates in metabolic reactions to synthesize or degrade carbohydrates, proteins, fats and nucleic acids. Zinc supports proteins functioning in many metabolic processes including stabilizing cell membranes and supporting immune function, growth and development.
Lower levels of Zinc are associated with loss of appetite and impotence.
One of the most important scientific studies on phytoestrogens (http://www.ncbi.nlm.nih.gov/pubmed/20043267) concludes: “The results show that a mixture of all tested PEs increased estradiol production and decreased testosterone production… indicating an induced aromatase activity. Furthermore, exposure of the H295R cells to isoflavonoids caused a decrease in testosterone production, and various mixtures of PEs significantly stimulated MCF-7 human breast adenocarcinoma cell growth and induced aromatase activity...
Overall, the results support that nutrition-relevant concentrations of PEs both alone and in mixtures possess various endocrine disrupting effects, all of which need to be considered when assessing the effects on human health.”
It is important to mention that this study worked with nutrition-relevant concentrations, meaning really the amount of phytoestrogens (PE) normally found in our diet.
The study mentions aromatase ester. This ester is responsible for turning testosterone into estrogen in both males and females. Several studies found that phytoestrogens enhance the effects of aromatase, thereby turning more testosterone into estrogen.
Another study, called Genistein decreases androgen biosynthesis in rat Leydig cells by interference with luteinizing hormone-dependent signaling (http://www.ncbi.nlm.nih.gov/pubmed/19059320) came to the following conclusion: “These observations imply that genistein action interferes with coupling of transmembrane luteinizing hormone receptors (LHR) with G proteins. Uncoupling of LHR from G proteins adversely affects adenylate cyclase function and impacts LH-dependent stimulation of Leydig cells. These findings have implications for testicular steroidogenesis in individuals exposed to genistein and soy-based products”.
In other words, soy phytoestrogens interfere with normal production of testosterone in male testes.
But it’s just minute amounts!
No, it’s significant. The results of a 2009 study by F. Eustache and colleagues are in its name: Chronic Dietary Exposure to a Low-Dose Mixture of Genistein and Vinclozolin Modifies the Reproductive Axis, Testis Transcriptome, and Fertility. (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2721872/?tool=pmcentrez )
Yes, low amounts, chronic exposure, serious consequences. Don’t be fooled.