There are many health practices which are re-evaluated by women once receiving their cancer diagnosis. Nutrition is certainly one of these. A healthy diet is one of several factors which affect the immune system. There is no food which will fully prevent your risk of breast cancer or recurrence. However, some simple guidelines for cancer prevention include increasing intake of fruits, vegetables and whole grains; fat consumption less than 30% of total daily caloric intake; alcohol consumption in moderation; and achieving and maintaining a healthy weight.
It was once thought soy products (e.g. tofu) would increase the risk of breast cancer as they contain isoflavones, which are plant estrogen. However, soy does not contain high enough levels to increase breast cancer risk. Eating a moderate amount of soy products (e.g. 1-2 servings per day) does not increase your risk. Supplements with soy however do have higher concentrations of isoflavones and should be avoided.