Vitamin B12 is needed for making DNA in every cell, for making neurotransmitters, and for keeping nerves and blood cells healthy. Vitamin B12 prevents anemia, a condition which can cause people to feel weak, tired and short of breath.
Dietary sources of vitamin B12 include red meat, fish, poultry, eggs, and dairy products.
The three main causes of a vitamin B12 deficiency are low dietary intake of Vitamin B12, poor absorption, and genetic defects that hinder the activation of this nutrient. Vegans and vegetarians are among those who are the most likely to have a B12 deficiency due to low dietary intake. Those who have had a gastric bypass, intestinal surgery and those with GI inflammation are also likely to be B12 deficient. Taking metformin, a diabetic drug, Prilosec or other acid blockers also increases the risk of malabsorption of B12.
Adequate levels of stomach acid, pancreatic enzymes and intrinsic factor are all necessary for proper absorption of Vitamin B12. People with pernicious anemia have antibodies against intrinsic factor, which is need for the absorption of this nutrient, causing these people to become B12 deficient and possibly anemic as well.
Some people have a defect in an enzyme called methyltetrahydrofolate reductase, or MTHFR, in the methylation pathway. This common
genetic defect, which inhibits the conversion of B12 to its active form, is present in about 60% of the US population. People with this genetic defect may have a normal or elevated serum B12 level, but their intracellular level of this nutrient could still be low. In this case, they would need to take B12 (and folate) in their methylated, or active form. Methylcobalamin is readily utilized by the body and is water soluble so it safe to use.