Soy can also supplement radiation therapy in treating prostate cancer by reducing side effects. A 2010 study in Nutrition and Cancer had one group of prostate cancer patients take 200 milligrams of soy isoflavone a day while another took a placebo. After six months, the group that took the soy isoflavones had less urine leakage, less diarrhea, and less bowel-related pain. Taking soy was also more likely to enable erections.

When your body breaks down the isoflavones in soy, they’re more easily absorbed and processed by the liver, according to a 2017 review in Nutrients. Because these isoflavones act like estrogen, they bind to an estrogen receptor in prostate tissue to reduce cancer growth and lower proteins that factor into the development of prostate cancer.

A 2022 review in Frontiers in Nutrition found that soy can also reduce the risk of other cancers by 10%. You can reduce your risk of cancer by 4% for each 25 grams of soy or 10 grams of soy isoflavones you consume per day. Although your risk of prostate cancer drops by 12% by eating soy, you can lower your risk of lung cancer by 33%. Soy or soy isoflavones aren’t associated with lowering your risk of dying of cancer.