What does B12 do in the brain?
Vitamin B12 is essential for neurological health, supporting nervous system function and cognitive processes such as memory and thinking. B12 is especially important for maintaining these functions as we age, and low levels have been linked to cognitive decline, dementia, and stroke.1
- Myelin
B12 is required for the DNA synthesis of oligodendrocytes and their production of myelin. The myelin sheath is the layer of insulation around the axon of nerve cells (neurons), similar to a plastic coating around an electrical wire. This insulation allows signals to travel quickly and efficiently between the brain, spinal cord, and body, which is essential for thinking, coordinated movement, reflexes, and communication throughout the nervous system.2 - Glial migration and synapse formation
B12 regulates signaling pathways that guide the organization of neural cells and the formation of synapses, ensuring neurons establish proper connections.3 B12 is also required for the formation of synapses; junctions where neurons communicate by transmitting signals. Deficiency can impair synaptic development and the positioning of specific glial cells (cells of the nervous system), ultimately affecting neural communication and brain function.4 - Metabolizing fatty acids
B12 functions as a coenzyme in the conversion of methylmalonyl coenzyme A (CoA) to succinyl CoA, a process required for the metabolism of fatty acids. Without adequate B12, abnormal fatty acids can be incorporated into myelin, weakening its structure and function.5 - Homocysteine metabolism
B12 works alongside folate and B6 to convert homocysteine into methionine. Homocysteine is an amino acid naturally produced in the body that can increase inflammation and damage to blood vessels when elevated. Hyperhomocysteinemia is linked to neurodegenerative decline and dementia.6
The homocysteine-methionine conversion is also essential for the generation of S-adeno-sylmethionine, a methyl donor involved in the methylation of DNA and the synthesis of lipids, proteins, and neurotransmitters in the nervous system.7 - DNA synthesis
DNA synthesis and repair is critical for neurogenesis (the creation of new neurons), and enabling synaptic plasticity: the ability of neuronal connections to strengthen or weaken in response to activity.
Insufficient B12 can result in limited methyl groups and nucleotides, which then impairs cell regeneration and proliferation. Impairments to DNA methylation or the proper repair of DNA itself can then lead to neuronal dysfunction and cognitive decline, especially in older people.8 - Mood regulation
B12 is a cofactor in creating S-adenosylmethionine (SAMe). SAM is a vital methyl group donor that goes on to produce serotonin and dopamine. Deficiency in B12 can result in reduced production of neurotransmitters, potentially leading to mood disorders such as depression.9
