The issue of soy and ER+ breast cancer is certainly confusing and we don't have all the information yet.   At this this time, the American Cancer Society and American Insitute for Cancer Research have issued guidelines that say that about 2 servings of whole soy foods,  one serving is equal to 3 ounces of tofu or tempeh, or 1/2 cup of soy beans, is safe.   They do not recommend soy protein  powders, or products with soy protein isolate.    There are also many  products that have soy oil, soy sauce, or soy lecithin, all of which are safe.    At this time, flax is considered safe, as it does not have the same plant chemical as soy.