Soy foods contain several key nutrients and phytochemicals studied for their cancer prevention properties. Many soy foods also contain dietary fiber, which may lower risk of colorectal cancer.
Soy foods contain isoflavones, which are phytoestrogens that in some ways mimic the action of estrogen but are very weak. Because high levels of estrogen link to increased breast cancer risk, there was a fear that soy foods—and the isoflavones in them— could increase risk. Yet overall, human studies show soy foods do not increase risk and in some cases, research suggests soy may lower risk.
For breast cancer survivors, population studies do not show any harmful interactions between soy foods and anti-estrogen medications. A small number of studies even suggest soy foods may be most protective for women who take anti-estrogen agents or aromatase inhibitors, but more research is needed before experts do more than encourage moderate consumption of whole soy foods (1 to 2 servings per day) as a low-fat protein.
According to epidemiologic studies it showed that consumption of soy foods is associated with a reduction in colorectal cancer risk in women, but not in men however still further investigations with strong dietary assessment tools and appropriate adjustment for confounding factors are needed to determine the potentially protective role of dietary soy and isoflavones in colorectal cancer etiology.
In conclusion, based on several studies above soy contain a lot of nutrients include phytochemicals and fiber that can help reduce risk of colorectal cancer but function of soy to cure cancer cells still need to have further human clinical studies.