Vitamin B12, also known as cobalamin, is a water-soluble nutrient that occurs naturally in foods such as meat, fish and milk products. The Institute of Medicine of the National Academies (IOM) hasn't established a tolerable upper intake level for vitamin B12 because it has little potential to be toxic when consumed through dietary sources or supplementation. However, the overconsumption of vitamin B12 isn't necessarily safe. Always talk to your treating physician before taking vitamin B12 supplements to address your health concerns.
Vitamin B12 Information
Vitamin B12 and other B vitamins are essential for a healthy metabolism; they convert carbohydrates into glucose, which your body uses for energy. Vitamin B12 encourages healthy nerve functioning and helps you produce RNA and DNA. Vitamin B12 and vitamin B9, or folate, act in concert to form healthy red blood cells and help your body use iron, states the University of Maryland Medical Center. Vitamin B12 supplements are primarily used to address a deficiency in this nutrient. Supplemental vitamin B12 is used to treat pernicious anemia and megaloblastic anemia. Other populations may benefit from increased amounts of vitamin B12. The IOM indicates that between 10 and 30 percent of older adults have difficulty absorbing vitamin B12. Supplemental vitamin B12 may also benefit vegans and vegetarians, any person who has had surgery on his digestive tract and those with digestive disorders that prevent vitamin B12 absorption, such as Crohn's disease and celiac disease.
Supplement Dosages
Tufts Medical Center indicates that vitamin B12 is delivered in high dosages when used therapeutically, typically between 100 and 2,000 mcg daily. Dietary sources supply far less vitamin B12; for example, a slice of beef liver gives you 48 mcg of vitamin B12, or 800 percent of your daily value based on a 2,000-calorie diet. Vitamin B12 appears to be very safe, even when consumed or taken in large amounts. However, supplemental vitamin B12 may have the potential to cause negative side effects. For example, Tufts indicates that large dosages of vitamin B12 may make acne worse.
Vitamin B12 Cautions
Although large doses of vitamin B12 either from food or supplements aren't usually associated with adverse effects, talk to your treating physician before taking supplemental vitamin B12 to address your health concerns. Avoid taking vitamin B12 supplements if you have Leber's disease; this may lead to blindness. MedlinePlus indicates that although there's sufficient evidence to support its use for vitamin B12 deficiency, anemia and low levels of vitamin B12 caused by certain diseases, there's less evidence to suggest that it's definitively helpful for other purposes, such as hyperhomocysteinemia, macular degeneration, stroke prevention, Alzheimer's disease, chronic fatigue syndrome and cancer prevention. Several medications can affect how well you absorb vitamin B12, including anticonvulsants, chemotherapy drugs, proton pump inhibitors and certain medications used to treat gout, diabetes and high cholesterol.
Recommended Amounts
According to the U.S. Office of Dietary Supplements, most Americans get enough vitamin B12 from dietary sources. The recommended dietary allowance for vitamin B12 for males and females age 14 and older is 2.4 mcg a day. Pregnant and nursing women have an RDA of 2.6 and 2.8 mcg of vitamin B12, respectively. Food sources of vitamin B12 include beef liver, clams, fortified breakfast cereals, rainbow trout, haddock, tuna, ground beef, steak, yogurt, cheese, milk, ham, eggs and chicken.
References
- Tufts Medical Center: Vitamin B12; August 2011
- Linus Pauling Institute at Oregon State University: Vitamin B12; J. Higdon, Ph.D.; March 2003
- U.S. Office of Dietary Supplements: Vitamin B12
- University of Maryland Medical Center: Vitamin B12 (Cobalamin); June 2009
- Institute of Medicine: Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline; June 2000
- MedlinePlus Medical Encyclopedia: Vitamin B12; February 2011
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