Milk in the Land, an inventively historicized documentary, unearths the sundry political, moral, and scientific platforms that got milk to its current post as beleaguered alpha beverage. Directors Ariana Gerstein and Monteith McCollum also present several opposing views as to whether it "does a body good," cleverly exploiting the symbolic value of a fluid that's as essentially American as the oil flowing through There Will Be Blood's veins.