Vitamin B12 in Health and Disease

Abstract

Vitamin B₁₂ is essential for DNA synthesis and for cellular energy production. This review aims to outline the metabolism of vitamin B₁₂, and to evaluate the causes and consequences of sub-clinical vitamin B₁₂ deficiency. Vitamin B₁₂ deficiency is common, mainly due to limited dietary intake of animal foods or malabsorption of the vitamin. Vegetarians are at risk of vitamin B₁₂ deficiency as are other groups with low intakes of animal foods or those with restrictive dietary patterns. Malabsorption of vitamin B₁₂ is most commonly seen in the elderly, secondary to gastric achlorhydria. The symptoms of sub-clinical deficiency are subtle and often not recognized. The long-term consequences of sub-clinical deficiency are not fully known but may include adverse effects on pregnancy outcomes, vascular, cognitive, bone and eye health.