Recent study results indicate that consuming soy protein can lower blood pressure. There are also some laboratory studies reported by the American Institute for Cancer Research suggesting that consuming soy early in life (around adolescence) may help protect against breast cancer later in life (the evidence for prevention when consuming soy later in life is not very promising). The only contraindication to soy ingestion is for women receiving anti-estrogen treatments such as tamoxifen for breast cancer.
Soy isoflavone is the substance responsible for the health benefit in the blood pressure study. Those consuming at least 2.5 milligrams or more of this soy substance lowered their blood pressure. Just an 8-ounce glass of soy milk has about 22 milligrams of isoflavones, which is more than enough to reap the benefits. So, if you have high blood pressure, you might want to grab a container of soy milk from the grocery store dairy case. And if you have a young daughter, you might consider including a bit of soy in her diet each day to reap the future benefit of having a lower risk of breast cancer.
Source: CARDIA trial reported by American College of Cardiology, 2012; American Institute for Cancer Research website, 2012