Soy has been linked soy to a number of health benefits, including protection against certain types of cancer and lower cholesterol levels. These benefits are largely attributed to a soy substance known as isoflavones. These compounds, which mimic human estrogen, are the focus of much research on soy and human health. While soy isoflavones contain certain health benefits, high consumption of them may also increase the risk for certain cancers.
- Isoflavones, active substances in soy based foods, are a class of phytoestrogens, compounds that exist in plants structurally akin to estrogen that have estrogen-like properties. Once in the body, these phytoestrogens behave like human estrogen. In some tissues they can mimic the effects of estrogen. Meanwhile, in other tissues they can block estrogen. Since the effects of isoflavones are not fully understood, concern exist about their longterm effects on our hormonal system.
- Estrogen and Breast Cancer. Estrogen is a hormone that can cause breast cancer in humans and animals. Thus, concern exists about the potential for high intakes of the estrogen-like compounds, like soy isoflavones, to negatively affect breast cancer survivors. According to University Of Maryland Medical Center, some research shows that soy can stimulate breast cancer cell growth According to the Linus Pauling Institute, the data in this area may conflict, but it is inadvisable for breast cancer survivors to eat high amounts of isoflavone-rich foods. Plus, pregnant mothers should avoid isoflavone-rich diets due to lack of research on soy’s effects on fetal development.
- Soy in Moderation. While the link between breast cancer and soy isoflavones has been studied in different ways, research has not provided clear answers regarding their effects on breast cancer risk. One is usually advised to eat soy foods in moderation and avoid soy-based supplements. According to the Penn State College of Agricultural Sciences, soy supplements, like soy protein, can have different effects on the body due to their high levels of levels of isoflavones.
- Recommended Levels. The Penn State College of Agricultural Sciences suggests that a safe intake of soy isoflavones is between 35 to 55 milligrams per day. Approximately two to three servings of natural soy foods per day is deemed safe. Per 3.3 ounce serving, boiled soybeans contain the highest level of isoflavones, with 54 milligrams, followed by tofu at 28 milligrams and soy hot dogs at 15 milligrams. One 8-ounce cup of soy milk contains 24 milligrams of soy isoflavones.