The China Study examines the relationship between the consumption of animal products (including dairy) and chronic illnesses such as coronary heart disease, diabetes, breast cancer, prostate cancer and bowel cancer.The authors conclude that people who eat a whole-food, plant-based/vegan diet—avoiding all animal products, including beef, pork, poultry, fish, eggs, cheese and milk, and reducing their intake of processed foods and refined carbohydrates—will escape, reduce or reverse the development of numerous diseases. They write that "eating foods that contain any cholesterol above 0 mg is unhealthy."
The book recommends sunshine exposure or dietary supplements to maintain adequate levels of vitamin D, and supplements of vitamin B12 in case of complete avoidance of animal products. It criticizes low-carb diets, such as the Atkins diet, which include restrictions on the percentage of calories derived from carbohydrates, which would, by quantity, reduce the benefits of complex carbohydrates. The authors are critical of reductionist approaches to the study of nutrition, whereby certain nutrients are blamed for disease, as opposed to studying patterns of nutrition and the interactions between nutrients.
The book is loosely based on the China-Cornell-Oxford Project, a 20-year study – described by The New York Times as "the Grand Prix of epidemiology" – conducted by the Chinese Academy of Preventive Medicine, Cornell University and the University of Oxford. T. Colin Campbell was one of the study's directors. It looked at mortality rates from cancer and other chronic diseases from 1973–75 in 65 counties in China; the data was correlated with 1983–84 dietary surveys and blood work from 100 people in each county. The research was conducted in those counties because they had genetically similar populations that tended, over generations, to live and eat in the same way in the same place. The study concluded that counties with a high consumption of animal-based foods in 1983–84 were more likely to have had higher death rates from "Western" diseases as of 1973–75, while the opposite was true for counties that ate more plant foods.