Vitamin D3 passes through breastmilk. It's recommended that nursing mothers get 5000-7000 IUs daily (which is then enough for mom and nursling). Current research that is taught and supported by LLL says that we do not get enough VitD from sunlight and that everyone should be supplemented.
You can always get your (and/or baby's) levels checked to see if it's needed.
Single Mommy to my 3 year old DS born all natural
. We are a Cosleeping
, Babywearing Non-Vaxing