Despite years of extensive research, cancer continues to pose a significant health challenge, primarily due to the lack of a comprehensive theory that brings together the various observations about the disease. This book aims to shed light on the evidence that suggests cancer is predominantly a metabolic disease, rather than a genetic one.

Regardless of their cellular or tissue origin, cancer cells display common metabolic abnormalities. One of these is the increased uptake of glucose and its fermentation into lactate, even in the presence of oxygen. This phenomenon, known as the Warburg effect, suggests that the mitochondria in these cells are not functioning properly.

The somatic mutation theory suggests that cancer develops from accumulated mutations in oncogenes and tumor suppressor genes. However, this theory is challenged by the fact that most cancers show significant genetic diversity within the same tumor, which contradicts the idea that specific mutations are the primary cause. Furthermore, while gene mutations are rare, cancer cells often exhibit extensive mutations.

The Warburg effect, a common metabolic characteristic of cancer cells, points to impaired respiration as the root cause of cancer. Warburg's hypothesis suggests that an irreversible injury to cellular respiration is the primary cause of cancer, forcing cells to depend on fermentation for energy. While subsequent research has focused more on gene mutations as the cause of cancer, emerging evidence supports Warburg's original hypothesis.

It is likely that mitochondrial dysfunction occurs first and then leads to the genome instability that accompanies tumorigenesis. Therefore, restoring normal respiration could be an effective strategy for preventing and treating cancer. By focusing on cancer metabolism, a unifying theory can be developed to integrate the diverse observations about cancer, which could potentially lead to the defeat of this disease.