"B-12 deficiency can cause anemia, and, if the deficiency is severe enough, irreversible nerve damage may occur. B-12 is also required, along with folate and B-6, to maintain low homocysteine levels. However, true deficiency of this vitamin is rare. Vitamin B-12 is found in abundant quantity in meat, dairy products and eggs, and the body can store enough B-12 to last for years. Note, though, that B-12 is not found at useful levels in any purely plant-based substance. For this reason, total vegetarians (vegans) need to take a B-12 supplement. Deficiency might also occur in people with low stomach acidity, such as seniors or those taking drugs that reduce stomach acid (such as Prilosec or Zantac). The reason is that stomach acid is required to separate B-12 from the proteins in which it is naturally found. People with low stomach acid can still absorb the purified B-12 found in supplements. The RDA is 0.9 mcg for children 1 to 3, 1.2 mcg for those 4 to 8, and 1.8 mcg for those 9 to 13. For individuals 14 years and older the RDA is 2.4 mcg. However, the RDA for pregnant women is 2.6 mcg and for lactating women it is 2.8 mcg. ULs have not been established for vitamin B-12."
