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Vitamin B12

Health Benefits, Uses, Side Effects & More

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Updated April 11, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Vitamin B12 is an essential nutrient found in many foods, especially animal products. Also available in supplement form, vitamin B12 is involved in regulating metabolism. In addition, vitamin B12 aids in the formation of red blood cells and in the maintenance of the central nervous system. Vitamin B12 is also required for the proper function and development of the brain.

Health Benefits of Vitamin B12

Studies suggest that vitamin B12 may help prevent or manage a number of health conditions, including:

1) Eczema

When applied to the skin, vitamin B12 may help fight eczema. For a 2004 study from the British Journal of Dermatology, researchers assigned 49 eczema patients to eight weeks of twice-daily treatment with a placebo or a cream containing vitamin B12. By the study's end, those using the vitamin B12 cream had experienced a greater decrease in the severity of their eczema (compared to those using the placebo cream).

See Natural Remedies for Eczema for other natural approaches.

2) Heart Disease

Taking vitamin B12 may lower your levels of homocysteine (an amino acid thought to increase heart disease risk when it is present in elevated levels). According to a 2000 report from Seminars in Thrombosis and Hemostasis, daily supplementation with both .5 to 5 mg of folic acid and about .5 mg of vitamin B12 may significantly reduce homocysteine levels.

For other ways to prevent heart disease naturally, see Natural Remedies for Heart Disease Prevention.

3) Cancer

Early research indicates that vitamin B12 may protect against some forms of cancer. In a 2003 study from Cancer Causes & Control, for instance, scientists examined the dietary habits of 214 women with cervical dysplasia. (A condition marked by abnormal changes in the cells on the surface of the cervix, cervical dysplasia can lead to cervical cancer if not treated.) Analyzing their findings, the study's authors determined that women who use vitamin B12 supplements and have a high intake of folate, riboflavin, and thiamin may be less likely to develop cervical cancer.

Related: Other Remedies for Cancer

More Research

According to the National Institutes of Health, vitamin B12 may not be effective for sleep disorders and stroke prevention.

Why Do People Take Vitamin B12?

People use vitamin B12 for a wide variety of health purposes, including prevention and/or treatment of the following conditions:

Vitamin B12 is also used to enhance mood, increase energy, improve memory, stimulate the immune system, promote healthy sleep, and slow the aging process.

Signs of Deficiency

Vitamin B12 deficiency is most common among adults over age 50, vegetarians, vegans, people who have undergone gastrointestinal surgery, and people with digestive disorders (such as celiac disease and Crohn's disease).

Signs of vitamin B12 deficiency include:

  • anemia
  • loss of balance
  • numbness or tingling in the arms and legs
  • weakness

Foods with Vitamin B12

To meet the recommended dietary allowance (RDA) for vitamin B12, include the following foods in your diet:

  • fortified cereal (1.5 to 6 mcg per serving)
  • wild rainbow trout (5.4 mcg per 3-ounce serving)
  • sockeye salmon (4.8 mcg per 3-ounce serving)
  • plain yogurt (1.4 mcg per cup)
  • white tuna (1 mcg per 3-ounce serving)
  • milk (.9 mcg per cup)
  • eggs (.6 mcg per egg)
  • roasted chicken (.3 mcg per half-breast)

The RDA for vitamin B12 is 2.4 mcg/day for all people ages 14 and older. If you're concerned that you're not getting enough vitamin B12 from food, talk to your doctor about using vitamin B12 supplements.

Side Effects

Although vitamin B12 is likely safe for most people, it may cause certain side effects (including diarrhea, blood clots, itching, and severe allergic reactions). In addition, combining vitamin B12 with chloramphenicol (an antibiotic medication) may produce harmful effects.

Vitamin B12 should be avoided by people with Leber's disease (a type of eye disease). When taken by people with Leber's disease, vitamin B12 can damage the optic nerve and possibly contribute to blindness.

Should You Take Vitamin B6 with Vitamin B12?

Some research suggests that taking vitamin B12 in combination with other B vitamins may be helpful for some conditions. For instance, taking vitamin B12, vitamin B6, and folic acid together may help treat hyperhomocysteinemia (a condition linked to heart disease). There's also evidence that taking vitamin B12 with vitamin B6 and folic acid might help prevent age-related macular degeneration.

Vitamin B12 Injections

Vitamin B12 injections are typically used to treat vitamin B12 deficiency in people who have trouble absorbing the vitamin (such as individuals with digestive disorders). Although some proponents suggest that vitamin B12 injections can also help promote weight loss, there's no evidence to support this claim.

Sources:

Christen WG, Glynn RJ, Chew EY, Albert CM, Manson JE. "Folic acid, pyridoxine, and cyanocobalamin combination treatment and age-related macular degeneration in women: the Women's Antioxidant and Folic Acid Cardiovascular Study." Arch Intern Med. 2009 Feb 23;169(4):335-41.

Clarke R, Armitage J. "Vitamin supplements and cardiovascular risk: review of the randomized trials of homocysteine-lowering vitamin supplements." Semin Thromb Hemost. 2000;26(3):341-8.

National Institutes of Health. "Vitamin B12: MedlinePlus Medical Encyclopedia". August 2011.

National Institutes of Health. "Vitamin B12: MedlinePlus Supplements". August 2011.

Office of Dietary Supplements. "Dietary Supplement Fact Sheet: Vitamin B12". Last accessed August 2011.

Stücker M, Pieck C, Stoerb C, Niedner R, Hartung J, Altmeyer P. "Topical vitamin B12--a new therapeutic approach in atopic dermatitis-evaluation of efficacy and tolerability in a randomized placebo-controlled multicentre clinical trial." Br J Dermatol. 2004 May;150(5):977-83.

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