Julie Burstein fills in for Leonard Lopate. On today’s show: Mark Bittman discusses why he believes taxing unhealthy foods is good policy. The director of the new documentary “Senna,” talks about the Brazilian race car driver Ayrton Senna. Oliver Pötzsch discusses his novel, The Hangman’s Daughter. Plus, Holly Finn describes undergoing many rounds of in vitro fertilization and the challenges of waiting too long to have a baby.