1 to 3 years: 0.9 mcg per day
4 to 8 years: 1.2 mcg per day
9 to 13 years: 1.8 mg per day
14+ years: 2.4 mg per day
Vitamin B-12 is found naturally in meats, poultry, seafood, eggs, and dairy products -- foods that are high in protein. Supplementation should not be necessary for healthy adults, except for vegans, as vitamin B-12 is only found in animal products. Ovolactovegetarians will get vitamin B-12 from eggs or dairy products. People with medical disorders such as pernicious anemia, celiac disease, atrophic gastritis or Crohn's disease may be at risk for vitamin B-12 deficiency.
Taking vitamin B-12 supplements will reduce homocysteine levels in your blood if they are elevated. Unfortunately taking the supplements doesn't appear to reduce your risk of cardiovascular disease. Vitamin B-12 supplements have also been recommended for improving cognitive skills and to boost energy, although research hasn't provided sufficient evidence for these recommendations.
"Vitamin B12." Accessed March 17, 2009. http://ods.od.nih.gov/factsheets/vitaminb12/.Otten JJ, Hellwig JP, Meyers LD. "Dietary Reference Intakes: The Essential Guide to Nutrient Requirements." IOM, 2006.