What Is the Purpose of B-12 in Your Body?

Clams are among the richest sources of vitamin B-12.

Clams are among the richest sources of vitamin B-12.

Vitamins help maintain normal function of your organs and tissues, and the eight vitamins of the B complex are no exception. One of these, vitamin B-12, is especially important in helping your nervous system function properly and in supporting many critical cellular reactions that ensure your survival. Consuming appropriate amounts of vitamin B-12 may also help you avoid several potentially serious diseases.


Vitamin B-12 is the largest and most complex of all vitamins, according to the Linus Pauling Institute. Also called cobalamin, it is the only vitamin that contains a metal, cobalt. Like all B vitamins, vitamin B-12 helps your body convert carbohydrate nutrients into glucose, a critical energy source which travels in your blood to reach your cells. Your body also uses the vitamin to produce red blood cells that carry oxygen to your tissues and to manufacture DNA and RNA, the genetic material in your cells. Vitamin B-12 also cooperates with vitamins B-6 and B-9 to lower blood levels of an amino acid called homocysteine, a potentially harmful compound.

Disease Prevention

Vitamin B-12 may help you avoid several disorders, including cardiovascular disease and cancer. A high blood level of homocysteine is a risk factor for heart disease, according to the Linus Pauling Institute, and research suggests that vitamin B-12 helps reduce homocysteine levels. A study published in "Lancet" showed that in human subjects with normal levels of vitamin B-9, which also affects homocysteine, vitamin B-12 was the most important factor in keeping homocysteine low. The authors suggested that both vitamins are potentially important in reducing the risk of cardiovascular disease. Other studies suggest that vitamin B-12 helps reduce cancer risk. In a study in "Cancer Epidemiology, Biomarkers and Prevention," breast cancer risk was more than 60 percent lower in women with high a intake of vitamin B-12 compared to women who consumed little of the vitamin.


In addition to potentially raising your risk of heart disease and cancer, a deficiency in vitamin B-12 can cause serious problems in your body. Because the vitamin is needed by your nervous system, a deficiency might cause you to experience neurological symptoms, such as tingling of your hands or feet, poor memory, mental confusion or difficulty maintaining your balance. A severe deficiency in vitamin B-12 may lead to a serious disorder called pernicious anemia, which occurs when your body is unable to absorb the vitamin from your food. Symptoms of the condition include fatigue, weakness, loss of appetite, constipation and weight loss. In infants and children, a vitamin B-12 deficiency can cause poor growth, problems with movement and a general delay in development.

Recommendation and Sources

According to the Office of Dietary Supplements, the recommended dietary allowance for vitamin B-12 is 2.4 micrograms for adults, with slightly more for pregnant or breast-feeding women. Children need between 0.5 and 1.8 micrograms, depending on age. Vitamin B-12 is found in fish, animal-based foods and dairy products but not in plant-based foods. Clams are especially good sources, with 84 micrograms in 3 ounces, as are most types of fish, with 3 to 5 micrograms per serving, and beef, with about 1 microgram per serving. Foods such as breakfast cereals are often fortified with vitamin B-12. Check labels to determine the amount. Vitamin B-12 supplements are also available in various formulations. Check with your doctor to decide if these supplements might be helpful for you.

About the Author

Joanne Marie began writing professionally in 1981. Her work has appeared in health, medical and scientific publications such as Endocrinology and Journal of Cell Biology. She has also published in hobbyist offerings such as The Hobstarand The Bagpiper. Marie is a certified master gardener and has a Ph.D. in anatomy from Temple University School of Medicine.

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