Hi first of all congratulations for becoming a new mom .. during breastfeeding you can use any protein powder unless you are diabetic you have to use sugar free protein powder..and coming to your diet you can have all vegetables and fruits .. nothing is harmful to you or your baby ..but most important and best foods are green leafy vegetables, fish, eggs, bread, milk, nuts, oats , Fenugreek which can increase your milk supply..but milk supply increases on demand so when you feed your baby more frequently, your milk production also increases