Vitamin B12, also called cobalamin, is a water-soluble vitamin that plays essential roles in nervous system function, in red blood cell formation, and is involved in the metabolism of every cell of the human body. It is a cofactor in DNA synthesis, and in both fatty acid and amino acid metabolism.
Unfortunately 40% of the population is deficient in Vitamin B12. Deficiency results in many neurological problems including myelopathy (spinal cord disease), neuropathy (nerve disease), and psychiatric problems ranging from cognitive and behavioral problems to dementia. As a nootropic, Vitamin B12 is great for cognitive enhancement.
Vitamin B12 is an essential nootropic for healthy brain function. Vitamin B12 may have many nootropic benefits. Vitamin B12 has a great impact on cognitive function and neurological health. Vitamin B12 plays an important role in our nervous system (CNS), the production of red blood cells, digestion and brain function. It helps to inhibit anaemia and helps to enhance mood and energy levels. Having adequate levels of vitamin B12 is essential not only for our physical health but also our mental health.
The most common health benefits of Vitamin B12 include:
- Improves cognitive function 
- Supporting genetic health of brain tissue 
- Helps maintain energy levels 
- Improves memory and concentration 
- Helps people who have Alzheimer’s disease 
- Reduces depression and improves mood 
- Promotes immune system 
- Increases male fertility 
- Helps people who have diabetes 
- Promotes sleep 
- Improves heart health 
- Improves skin health and hair health 
- Helps people who are fighting cancer 
- Helps produce red blood cells and inhibit anemia 
There are many people who use vitamin B12 for amyotrophic lateral sclerosis (Lou Gehrig’s disease), multiple sclerosis, improving the eye disease age-related macular degeneration (AMD), a condition in which the body produces too much thyroid hormone, Lyme disease and gum disease. Vitamin B 12 also helps in digestion.
How it works
Vitamin B12 is recognized as to stimulate the synthesis of neurotransmitters and supports the formation of the protective myelin sheath, the insulating exterior which accelerates the transmission of electric impulses in neurons.
It preserves cell membrane structure which use methyl groups donated by vitamin B12 for the conversion of phosphatidylethanolamine to phosphatidylcholine. This reaction is crucial for mobilization of docosahexaenoic acid (DHA) from the liver, which makes it available for the brain cells.  Actually, the decreased mobilization of DHA from the liver into plasma and peripheral tissues in addition to high level of plasma homocysteine might be a contributing factor to cerebrovascular and neurodegenerative changes in the patients with Alzheimer’s.
Vitamin B-12 supplements are normally considered safe. However, high doses of vitamin B-12 may cause dizziness, headache, anxiety, nausea, and vomiting. Again taking vitamin B-12 with vitamin C may reduce the available amount of vitamin B-12 in your body. In order to avoid this interaction, you are recommended to take vitamin C at least 2 hours after taking a vitamin B-12 supplement.
The recommended dosage for vitamin B12 differs according to age and body need, but according to the Mayo Clinic, it is as follows: 
- 0–6 months: 0.4 micrograms
- 7–12 months: 0.5 micrograms
- 1–3 years old: 0.9 micrograms
- 4–8 years old: 1.2 micrograms
- 9–13 years old: 1.8 micrograms
- 14+ years old: 2.4 micrograms
Though the recommended daily amount of vitamin B-12 for adults is 2.4 micrograms, you can safely take higher doses. Your body absorbs only as much as it needs, and the excess passes through your urine.