Soy has been sold as a health food for quite a long time. Soybean oil, soy milk, and even tofu are a staple in the lives of many people, especially vegetarians. However, most soy products are not real food by any means — most are highly processed and genetically modified. In fact, soy oil was used during the Industrial Revolution to lubricate machinery. Still sound appetizing? The marketing of soy as a health food is probably one of the greatest bamboozles of all time.
What's the Problem With Soy?
One of the issues concerning soy is its high level of phytoestrogens, compounds that mimic estrogen in the body. Soy contains two primary phytoestrogens, often termed xenoestrogens. These include genistein and daidzein, and both compounds have harmful effects on the endocrine system in males and females. [1] All estrogen compounds fall into the category known as isoflavones, compounds that could, in theory, stimulate breast cancer cells.
http://www.globalhealingcenter.com/natural-health/5-facts-soy-estrogen/