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Vitamin B12

Vitamin B12 is a nutrient that helps keep the body’s nerve and blood cells healthy and helps make DNA, the genetic material in all cells. Vitamin B12 also helps prevent a type of anemia called megaloblastic anemia that makes people tired and weak.

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› Health benefits

Scientists are studying vitamin B12 to understand how it affects health. Here are several examples of what this research has shown:

Heart disease
Vitamin B12 supplements (along with folic acid and vitamin B6) do not reduce the risk of getting cardiovascular disease. Scientists had thought that these vitamins might be helpful because they reduce blood levels of homocysteine, a compound linked to an increased risk of having a heart attack or stroke.

Dementia
As they get older, some people develop dementia. These people often have high levels of homocysteine in the blood. Vitamin B12 (with folic acid and vitamin B6) can lower homocysteine levels, but scientists don’t know yet whether these vitamins actually help prevent or treat dementia.

Energy and athletic performance
Advertisements often promote vitamin B12 supplements as a way to increase energy or endurance. Except in people with a vitamin B12 deficiency, no evidence shows that vitamin B12 supplements increase energy or improve athletic performance.

› How much do I need?

The daily amount of vitamin B12 depends on age. For women, it increases during pregnancy and when lactating. Adults age 19-plus: 2.4 micrograms (mcg) daily. Pregnant women: 2.6 micrograms; breastfeeding women: 2.8 micrograms.

Most people in the United States get enough vitamin B12 from the foods they eat. But some people have trouble absorbing vitamin B12 from food. As a result, vitamin B12 deficiency affects between 1.5% and 15% of the public. Your doctor can test your vitamin B12 level to see if you have a deficiency.

Certain groups may not get enough vitamin B12 or have trouble absorbing it:
• Many older adults, who do not have enough hydrochloric acid in their stomach to absorb the vitamin B12 naturally present in food. People over 50 should get most of their vitamin B12 from fortified foods or dietary supplements because, in most cases, their bodies can absorb vitamin B12 from these sources.
• People with pernicious anemia whose bodies do not make the intrinsic factor needed to absorb vitamin B12. Doctors usually treat pernicious anemia with vitamin B12 shots, although very high oral doses of vitamin B12 might also be effective.
• People who have had gastrointestinal surgery, such as weight loss surgery, or who have digestive disorders, such as celiac disease or Crohn’s disease. These conditions can decrease the amount of vitamin B12 that the body can absorb.
• Some people who eat little or no animal foods such as vegetarians and vegans. Only animal foods have vitamin B12 naturally.

Vitamin B12 deficiency causes tiredness, weakness, constipation, loss of appetite, weight loss and megaloblastic anemia. Nerve problems, such as numbness and tingling in the hands and feet, can also occur.

› In food

Vitamin B12 is found naturally in a wide variety of animal foods and is added to some fortified foods. Plant foods have no vitamin B12 unless they are fortified. You can get recommended amounts of vitamin B12 by eating a variety of foods including beef liver and clams, which are the best sources of vitamin B12; fish, meat, poultry, eggs, milk and other dairy products, which also contain vitamin B12; and some breakfast cereals, nutritional yeasts and other food products that are fortified with vitamin B12.

> Dietary supplements

Vitamin B12 is found in almost all multivitamins. Dietary supplements that contain only vitamin B12, or vitamin B12 with nutrients such as folic acid and other B vitamins, are also available. The most common forms that it is available in are tablets, capsules, chewables and lozenges.

Source: National Institutes of Health, Office of Dietary Supplements

Please consult your health care provider before making changes to your vitamin/supplement regimen.

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