This article provides an in-depth analysis of the biochemical and physiological roles of folic acid (vitamin B9), focusing on DNA and RNA synthesis, cell division, methylation reactions, hematopoiesis, and embryonic development. The pathophysiological mechanisms of folate deficiency, global and regional epidemiological indicators, and clinical outcomes—including megaloblastic anemia, neural tube defects, cardiovascular diseases, depression, and cognitive impairment—are examined based on evidence-based data. Risk groups, folate requirements during pregnancy, the consequences of micronutrient deficiency, and the effectiveness of fortification programs are evaluated. The findings confirm that adequate folic acid intake is a crucial determinant for perinatal health, prevention of neonatal disabilities, and reduction of hematological and cardiometabolic risks.