Methylcobalamin, also known as Vitamin B-12, is a water-soluble, essential nutrient vital to human health. B12 was first discovered in the 1800s as compound found in liver that could be used to treat pernicious anemia (1). Deficiency of B12 has been implicated in numerous diseases. Since its structure was first discovered, it has been identified as an enzyme cofactor for DNA synthesis and energy production, and it may play a role in brain and nerve health as well (2).
Vitamin B12 supplementation is considered to be important to increasing energy, as well as aiding in the metabolism of fat, protein and carbohydrate (3). As an enzyme cofactor it has effects on decreasing plasma homocysteine (a biomarker of inflammation), and converting various enzymes that support energy metabolism (4). B12 is involved in the methylation process, meaning it can lend methyl groups to other molecules to support various metabolic processes (11, 12). Adequate levels of vitamin B12 have been associated with increased mood and well-being, and deficiencies are associated with depression, fatigue, and increased risk of stroke (5, 6, 7). Additionally, vitamin B12 is involved in healthy neuronal function and neurotransmission (8).
Vitamin B12 is absorbed through the intestines and carried in the bloodstream where it binds to transporter proteins (9). There are several different types of vitamin B12; methylcobalamin the active form in the body, has the greatest bioavailability and can cross the blood-brain barrier freely (10).