In Good Food, John McKenna starts with his personal experience of good, healthy food, growing up in the Irish countryside. From there he develops his experiences as a doctor in West Africa, encountering natural and simple diets, and how shocked he was on returning to the UK in 2003 at the foods which people were eating in the developed world.

Using ground-breaking work by medical researchers in the areas of natural and processed foods, he analyses the diet of a typical child in the modern developed world, showing both the nutrient and the toxic content of that diet. He explains why diseases such as diabetes, obesity, heart disease and cancer are on the increase and why learning difficulties and food intolerances are increasing at a phenomenal rate.

He sets out the cornerstones for healthy eating, giving examples of nutrient-rich diets and explaining why they are so good. He surveys the recent history of food processing, its apparently relentless advance, and analyses the damage it does. He shows how to reduce toxins in the common diet, how to change our ways of shopping and eating, and uses case histories of good and bad preparation of basic meals.