A: Yes, I think you should eat soy foods. Just don't overdo it: The evidence linking soy intake with breast cancer risk is mixed. When researchers compare the Japanese, who eat a lot of soy, to Americans, who eat very little, they find lower rates of breast and other cancers in the soy eaters. However, they've found that in a test tube, soy's plant estrogens can speed cancer cell growth.
Why the discrepancy? It may be that soy behaves differently in the body than it does in test tubes. Or soy may have both positive and negative influences on breast cancer. There's also the possibility that populations eating soy are actually benefiting from not eating something else, such as meat. The saturated fat in red meat has been linked to higher cancer risk. Replacing steak with tofu could be protective even if soy does not fight cancer directly.
These theories are intriguing, but a recent National Cancer Institute workshop on soy and breast cancer risk concluded that we still don't know enough to recommend soy for cancer prevention. And a solid answer, based on research, is still years away. In the interim, using soy in your diet as a replacement for meat is healthful overall. A moderate approach would be two to three soy-based meals per week. There are, of course, other proven strategies for reducing your risk of breast cancer, including moderate exercise, weight control, avoiding alcohol, and eating plenty of fruits and vegetables.