Dairy contains a balanced ratio of phosphorus (essential mineral for bone development) and calcium (needed for healthy bones, nerve function, blood clotting, muscle and heart contractions).  This is important because the ratio of phosphorus to calcium in dairy aids in calcium absorption and that's why including dairy in the diet is so important as you get older.  Even more so since we're more susceptible to osteoporosis as we age.  The good news is we can essentially side step this issue if we're absorbing calcium properly which dairy can provide.