The hormones in your body have a great impact on your health. Some foods, such as soy milk and other soy-based foods, contain substances that could affect hormonal signaling. In theory, this means that consuming soy milk could reduce your risk of developing breast cancer, though studies trying to measure the effects of soy on breast cancer can also be complicated by other factors.
Breast Cancer and Hormones
The cells in your breast respond to the levels of estrogen in your body. Breast cells typically grow in response to increased estrogen levels. Although breast cancer cells differ significantly from normal breast tissue, some types of breast cancer retain this response to estrogen. Consequently, changes in estrogenic signaling affect the growth of breast cancer cells, and elevated estrogen levels are often associated with an increased risk of developing breast cancer. Some breast cancer treatments take advantage of this trait and work to block estrogenic signaling.
Soy Milk and Phytoestrogens
Soy-based food products, including soy milk, contain substances known as isoflavones. These isoflavones function as antioxidants, which means that they prevent cell damage. Isoflavones are also chemically similar to estrogen and are sometimes known as phytoestrogens, the Harvard School of Public Health reports. Phytoestrogens have the ability to affect cells that respond to estrogen. Although phytoestrogens are similar to human estrogen, their subtle chemical differences mean that they could bind to and block the sites on cells that respond to estrogen, thus abrogating estrogenic signaling.
Soy and Breast Cancer
Consuming soy protein through products such as soy milk may be able to protect you from breast cancer, a large study published in 2009 in the "American Journal of Clinical Nutrition" explains. This study involved over 70,000 women from different parts of Shanghai between the ages of 40 and 70. The researchers examined the incidence of breast cancer in women based on how much soy they consumed on average over the course of seven years. Women who consumed large amounts of soy during adolescence and adulthood had a significantly reduced risk of developing breast cancer, which suggests that soy phytoestrogens have a protective effect, though this conclusion only applies to premenopausal breast cancer.
Considerations
Although this study suggests that consuming soy milk can protect you from breast cancer, there are some other factors that could affect these results, BreastCancer.org notes. Women who eat more soy typically consume less meat, which means they likely consume less fat and other substances, such as synthetic hormones, which are often given to animals to increase their size. Women who consume more soy may also have other aspects of their diets that are different or they may be closer to their ideal body weight. Both of these factors could contribute to the apparent protective effect of soy milk. More research needs to be done to clearly demonstrate the effects of phytoestrogens on breast cancer.
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