Greger focuses on heart disease, the leading cause of death in the United States, and argues that it is largely preventable through dietary changes. He explains how coronary heart disease develops, with plaque buildup in the arteries leading to heart attacks, and highlights how societies with plant-based diets, such as those in rural China and Africa, have significantly lower rates of heart disease. Greger critiques the heavy reliance on pharmaceutical interventions like statins, which, despite their effectiveness, come with risks and side effects. Instead, he emphasizes the potential of a whole-food, plant-based diet to prevent, stop, and even reverse heart disease, often more effectively than medication. The chapter also touches on the influence of industry and the medical establishment in shaping public dietary recommendations and the persistent underestimation of the power of diet in preventing heart disease.

Greger discusses lung diseases, particularly lung cancer, chronic obstructive pulmonary disease, and asthma, which collectively claim about 300,000 lives annually in the United States. Greger emphasizes the strong link between smoking and lung cancer, noting that the majority of cases are preventable. He highlights the potential of plant-based diets to mitigate the risks and progression of these diseases, particularly through the consumption of fruits, vegetables, and specific compounds like those found in broccoli and turmeric.