Why are humans so vulnerable to big promises about food? Emily Thomas meets some people who became convinced salvation lay in what they ate, and a neurologist who explains why food can make us lose our powers of critical thinking. Plus, the story of a woman who fooled hundreds of thousands of people - as well as vast corporations - into believing she’d cured brain cancer with her diet. *This is not a programme about a food that will save your life. (Picture: Black pot. Credit: Getty Images)