During the course of writing this book, I have often been asked what lessons I personally draw from it. Well, for me the history of expert advice on diet and health inevitably brings to mind the old saying, "This too shall pass." The massive reversals in expert opinions described in this book provide more than enough support for this skepticism. Indeed, the hubris of experts confidently telling us what to eat has often been well-nigh extraordinary. In 1921, for example, the consensus among the nation’s nutritional scientists was that they knew 90% of what there was to know about food and health. Yet just a few years earlier, before the discovery of vitamins, they had routinely condemned the poor for wasting their money on fresh fruits and vegetables, which were said to be composed of little more than water, with only minimal amounts of the protein, fats, and carbohydrates that were essential to life.