April 21, 2010 12:02 pm The Importance of Vitamin D Dr. Katherine Sherif, director of the Drexel Center for Women’s Health, explains why vitamin D is vital to our health. US & World Videos 1:47 New nationwide Xfinity ad features 3 Vietnam War vets as Military Appreciation Month begins 1:08 Philly police believe teenage girl stabbed grandmother to death inside rowhome 2:10 ‘You're speechless and can't believe what you saw.' Mom sees video of attack on her autistic son on SEPTA train 0:39 1 dead, 3 injured in Eastwick after two separate shootings, police say 0:22 Rescue crews call off search for missing kayaker in Schuylkill River