Li begins by emphasizing food’s powerful role in preventing and fighting disease. He introduces the concept of five defense systems—angiogenesis, regeneration, microbiome, DNA protection, and immunity—that are fundamental to health. Each system can be influenced by specific foods, offering an accessible way for individuals to protect their health without relying solely on expensive pharmaceutical treatments. Li draws on his experience as a medical doctor and biochemist, explaining how foods can stimulate beneficial biological responses, such as promoting stem cell regeneration or bolstering the immune system.

He outlines how certain everyday foods—such as soy, tomatoes, dark chocolate, and fermented products—affect these defense systems. He says scientific research is increasingly validating the link between diet and health. Li argues that food’s significance matches modern medicine’s, not as a replacement but as an additional, practical tool for disease prevention. His book serves as a guide for making informed food choices to promote long-term health and stave off chronic diseases like cancer, diabetes, and cardiovascular disease.

Li’s ultimate message is that by making mindful dietary choices, individuals can harness the natural defense mechanisms within their bodies to combat disease, improve quality of life, and potentially extend their healthy years.