made a strong recommendation for heart patients to change their diets, and the idea that improper diet could be one of the causes of cancer is now widely accepted. Still, the scientific understanding of the effect of food on health remains limited. Food is viewed most of the time only in terms of its nutrient content: It is“ low-fat,” or“ low-salt,” or“ low-calorie.” Dietary recommendations of modern nutritional science often run along the lines of“ Eat X amount of calories, Z grams of protein, and less sodium and fat.” If one takes all this seriously, it becomes necessary to cook dinner with the recipe book on one side and tables of food composition on the other. Not only is this far removed from the realities of the kitchen, but, as you will see in this book, the world of food and its effects on our health is infinitely more complex and interesting than that. I believe that it is an area of knowledge that, if incorporated into our medical system, can be extremely helpful to us all. Using food to stay well is a safe, effective, and generally inexpensive practice. As the costs of medical care increase, dietary management as a cost-effective alternative will become more and more attractive. Before we can do that, however, we have to reorient our understanding about the human organism, and what makes it healthy and unhealthy.