This book explores the complex interactions between B vitamins, iron and DNA synthesis, highlighting their crucial role in cellular metabolism. It describes in detail the biochemical functions of vitamins B12, B9, and B3, as well as iron, highlighting their impact on DNA methylation, red blood cell production and porphyrin regulation. The text examines the effects of deficiencies and excesses of these nutrients, such as pernicious anemia, neuropathies and porphyrias. By integrating a bioinorganic perspective, it reveals the underlying chemical mechanisms and molecular interactions. Chapters deal with the synergies between these nutrients, their influence on DNA repair, and modern methods for optimizing their absorption. Finally, the book proposes innovative directions for future research, such as the use of nanotechnology and the development of biosensors for precise nutrient monitoring. This work is aimed at biochemistry professionals, nutrition researchers and those interested in the molecular mechanisms of metabolism.