We are in the middle of a protein boom. Protein food products make up a more than $100 billion industry — and it’s still growing. In a new book, Protein: The Making of a Nutritional Superstar, health scholar Samantha King and sociologist Gavin Weedon reveal how marketing, industry interests, and cultural trends — not nutritional science — have turned protein into the most popular nutrient of the moment. King and Weedon sat down with Apple News In Conversation guest host Sam Sanders to talk about the real reason protein is everywhere, and how to think differently about your intake.