Vitamin B12 Functions
Vitamin B12 works with folate to make methionine, an amino acid important in the creation of proteins. Vitamin B12 important in energy metabolism, particularly in the creation of energy from fat and protein. Vitamin B12 maintains nerve sheaths and protects nerve fibers.
Vitamin B12 Deficiency
The main cause of vitamin B12 deficiency is lack of absorption. Vitamin B12 requires intrinsic factor to be absorbed. Many elderly people don’t produce enough intrinsic factor, so even if they are eating food sources with Vitamin B12, they can become deficient because the B12 is not absorbed. In these cases, higher intakes of Vitamin B12 are recommended, and Vitamin B12 is injected. Most people have adequate intakes of vitamin B12, but vegans are at risk as well. This is because Vitamin B12 is the only vitamin found ONLY in animal sources. Vegans typically take supplements and have adequate intrinsic factor, so although they are at risk, they are not as likely to have B12 deficiency as the elderly. Vitamin B12 deficiency can cause Pernicious Anemia. Because vitamin B12 is important in maintaining nerve sheaths, deficiency can result in a lack of sensation of the toes and the fingers. This can further progress up the legs and the arms and result in difficulty with movement and walking as well as disorientation and dementia.
Recommended Intake of Vitamin B12
Adult males and females need 2.4 ug per day.
Age and Gender |
Amount of Vitamin B12 per Day |
Infants 0-6 mo |
0.4 ug |
Infants 6-12 mo |
0.5 ug |
Children 1-3 yr |
0.9 ug |
Children 4-8 yr |
1.2 ug |
Males 9-13 yr |
1.8 ug |
Males 14 and up |
2.4 ug |
Females 9-13 yr |
1.8 ug |
Females 14 and up |
2.4 ug |
Food Sources of Vitamin B12
Vitamin B12 only occurs in animal foods. Good sources include:
For individuals who are vegan who don't eat any animal products, they should obtain B12 from supplements, fortified foods or nutritional yeast.
- clams
- mussels
- crab
- beef
- pork
- tuna
- turkey
- cheese
- egg
- milk
For individuals who are vegan who don't eat any animal products, they should obtain B12 from supplements, fortified foods or nutritional yeast.
References
- Brody, T. Molecules Important to Digestion and Absorption. In: Nutritional Biochemistry, 2nd ed. Academic Press. San Diego, CA. 1999: 81.
- Dietary Reference Intakes (DRIs): Recommended Dietary Allowances and Adequate Intakes, Vitamins. Food and Nutrition Board, Institute of Medicine, National Academies. United States Department of Agricultural. Last accessed April 2nd, 2016. https://fnic.nal.usda.gov/sites/fnic.nal.usda.gov/files/uploads/recommended_intakes_individuals.pdf
- Food Sources. Vitamin B12. Vitamins. Linus Pauling Institute Micronutrient Information Center. http://lpi.oregonstate.edu/mic/vitamins/niacin. Last updated January, 2014. Last accessed April 13, 2016.
Last updated on April 2nd, 2016
