Vitamin B12, also called cobalamin, is a water-soluble vitamin that play a key role in the normal functioning of the brain and nervous system.
It is involved in the metabolism of every cell of the human body, especially affecting DNA synthesis, fatty acid and amino acid metabolism.
Human body cannot produce vitamin B12, and substantial sources of B12 include animal products (shellfish, meat), fortified food products, and dietary supplements.
Vitamin B12 deficiency is a common cause of megaloblastic anemia, various neuropsychiatric symptoms, and other clinical manifestations.
Due to impairment of vitamin B12 absorption during aging, people over age 60 are at risk of deficiency.
Screening for vitamin B12 deficiency may be warranted in patients with one or more risk factors, such as gastric or small intestine resections, inflammatory bowel disease, use of metformin for more than four months, use of proton pump inhibitors or histamine H2 blockers for more than 12 months, vegans or strict vegetarians, and adults older than 75 years.
Initial laboratory assessment should include a complete blood count and serum vitamin B12 level.
Measurement of serum methylmalonic acid should be used to confirm deficiency in asymptomatic high-risk patients with low-normal levels of vitamin B12.
Researchers suggest that consuming high-dose vitamin B12 (1 to 2 mg daily) is as effective as intramuscular administration for correcting anemia and neurologic symptoms.
Intramuscular therapy leads to more rapid improvement and should be considered in patients with severe vitamin B12 deficiency or severe neurologic symptoms.
Vitamin B12 absorption rates improve with supplementation, and hence patients older than 50 years and vegans or strict vegetarians should consume foods fortified with vitamin B12 or take vitamin B12 supplements.
Patients who have had bariatric surgery should receive 1 mg of oral vitamin B12 per day indefinitely.
Use of vitamin B12 in patients with elevated serum homocysteine levels and cardiovascular disease does not reduce the risk of myocardial infarction or stroke, or alter cognitive decline.