Do not forget that whatever you eat, will reflect on the content from your mammary gland which comes out of your nipple. Example, when you breast feed your baby, the same happens to your milk.
There is also an other theory which underwire bras could be the cause of that problem. By wearing underwire bras, you are cutting off your mammary glands, your lymphatic and your circulatory system.
In order to see a change, you should look to correct these problems.
All my best