MayoClinic.com notes that cancer is the second biggest health issue for men, with leading cancers being prostate, lung, colorectal and skin. According to doctors Michael Murray and Joseph Pizzorno, soy’s high isoflavone content makes it the single best dietary factor in the prevention of prostate cancer. A 1-cup serving of soy milk contains approximately 30 percent of your daily calcium. As calcium helps to prevent colorectal and intestinal cancers, this adds to soy’s cancer-prevention properties. Additional benefits arise from soy milk’s antioxidants, which help to eliminate cancer-causing free radicals from your body. These include riboflavin and zinc, with 34.4 and 5.7 percent of your daily intake in a 1-cup serving, respectively.