This chapter emphasizes the vital role of nutrition in both cancer prevention and treatment, highlighting how dietary choices can significantly impact health. A balanced, plant-based diet rich in fruits, vegetables, fiber, and polyphenols is linked to reduced cancer risk, while harmful foods like processed meats, alcohol, and ultra-processed products increase the likelihood of cancer. Maintaining a healthy gut microbiome and following concepts like Hara Hachi Bu—eating until 80% full—can positively influence overall well-being. The chapter also cautions against over-reliance on dietary supplements, recommending their use only under medical guidance. For cancer patients, an adapted diet can alleviate symptoms and enhance quality of life, showcasing the importance of food synergy in fostering health and recovery.