Don't know the specific effects on the gallbladder, but there are lots of problems with milk. This link might provide you with some info:
www.notmilk.com
*One thing milk is good for...your skin! The lactic acid does just as good a job of exfoliating as any expensive AHA creams. I often wash my face with powdered milk...leaves it really soft and gets rid of the winter dry flakies!