How Much Vitamin B-12 Does Your Body Need?

Vitamin B-12, or cobalamin, is a member of the water-soluble family of B-complex vitamins. It's required for normal function of nerve cells, DNA production and your body need vitamin B-12 to make an adequate number of blood cells.

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.

The Health and Medicine Division of National Academies of Sciences, Engineering and Medicine determines the dietary reference intakes for vitamins and minerals. These DRIs are based on the nutritional needs of the average healthy person. The DRI for vitamin B-12 is based on age. Women who are pregnant or breastfeeding need just a little more.

Dietary Reference Intakes

1 to 3 years: 0.9 micrograms per day
4 to 8 years: 1.2 micrograms per day
9 to 13 years: 1.8 micrograms per day
14+ years: 2.4 micrograms per day
Women who are pregnant: 2.6 micrograms per day
Women who are breastfeeding: 2.8 micrograms per day

Vitamin B-12 Deficiency

Since vitamin B-12 is found in foods of animal origin, most people get enough in their diets. Individuals who have pernicious anemia can't absorb enough vitamin B-12 because they don't produce enough of a substance called intrinsic factor, which is essential for vitamin B-12 to be absorbed through the walls of the small intestine.

People with atrophic gastritis or diseases of the small intestine such as celiac disease or Crohn's disease, some types of weight-loss surgery, parasitic infestations or bacterial overgrowth can also reduce a person's capability to absorb vitamin B-12.

Such a deficiency can cause several different problems, such as megaloblastic anemia, which occurs when red blood cells can't develop properly.

A vitamin B-12 deficiency may cause neurological problems.

Symptoms due to the anemia include:

fatigue (feeling tired most of the time)
weakness in parts of your body
loss of appetite
weight loss
constipation

Neurological symptoms of vitamin B-12 deficiency may include any of these:

numbness and tingling in your hands or feet
loss of balance
depression
confusion and loss of memory
burning pain or soreness of mouth or tongue

Some people can have the neurological symptoms without the anemia, and all of these symptoms can come from other health problems. If you think you might have a vitamin B-12 deficiency, you need to see a health care provider who can determine if you have a vitamin B-12 deficiency by ordering special blood tests.

Vegans or individuals who eat very little foods of animal origin can take vitamin B-12 as a dietary supplement or eat vitamin-fortified cereal. Ovolactovegetarians should get vitamin B-12 from eggs or dairy products.

People who have been diagnosed with a vitamin B12 deficiency due to malabsorption may be given regular vitamin B-12 shots, which eliminate the need to absorb the vitamin through the small intestine, but in some cases taking the vitamin in a pill form may work.

It would be tough to use foods to prevent or treat vitamin B-12 deficiencies due to malabsorption, although eating large amounts of liver was an historical treatment for pernicious anemia.

Taking vitamin B-12 supplements will reduce homocysteine levels in your blood. 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. But research hasn't provided sufficient evidence for these recommendations either.

Sources:

Health and Medicine Division of National Academies of Sciences, Engineering and Medicine. "Dietary Reference Intakes Tables and Application." http://www.nationalacademies.org/hmd/activities/nutrition/summarydris/dri-tables.aspx.

Martí-Carvajal AJ, Solà I, Lathyris D. "Homocysteine-lowering interventions for preventing cardiovascular events." http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD006612.pub4/abstract;jsessionid=75EDDE8486AD1CE4C828AF5C72FB2BD4.f01t02.

National Institutes of Health Office of Dietary Supplements. "Vitamin B12." http://ods.od.nih.gov/factsheets/vitaminb12/.