Vitamin B12 deficiency: metabolic effects, clinical evaluation, and treatment

Vitamin B12 is a water-soluble essential micronutrient, required by all the body cells. Its deficiency has been implicated not only in hematological and neurological disorders, but also in many metabolic processes, such as insulin resistance and body composition changes, which have aroused particular interest in recent years. This study reviews the physiology of vitamin B12 from its digestion and absorption to its distribution in tissues, metabolic effects and controversies regarding the diagnosis of deficiency, and to dietary and pharmacological treatments.