It is a common misbelief that there is large quantities of estrogen in soymilk, which might cause men to become more feminine; both physically and mentally. This certainly is not the case.
I found this great article “Soy Protein and Estrogen Myths” written by Aijalyn Kohler on livestrong.com as well as some wonderful information from the manufacturer of the Silk soymilk brand, that helped summarize the issue. They explained that while soy milk does not contain the hormone estrogen it does have isoflavones , which are a type of phytoestrogens. Phytoestrogen is also known as a “plant estrogen”. The structures of isoflavones are very similar to the hormone estrogen, but the two function very differently in the body. When isolavones bind themselves to estrogen receptors they exhibit estrogen like behaviors and sometimes block the actual estrogen from working. Because of this many people have studied the possible beneficial effects of soy milk in the role of supporting heart and bone health, minimizing menopausal symptoms, as well as reducing the risk of breast cancer and osteoporosis.
In a study done by the American Society for Nutritional Sciences on the "Hormonal Effects of Soy on Premenopausal Women and Men" they concluded that while they found soy consumption to have small effects on hormones of both premenopausal women and men, it was generally in the beneficial direction.
Soy products have been consumed by eastern cultures for thousands of years, and they seem to be doing just fine. Japan is actually the leading country in the average life expectancy, while the United States trails behind in 36th place. What have we been doing wrong? While there are many articles about the benefits as well as the set backs of soy products, no substantial studies have proven that soy products cause men to become more feminine.