Vitamin B-12, also known as cyanocobalamin, is a water soluble vitamin essential for healthy nerve and red blood cell development. It plays a role in producing DNA, the genetic information found in body cells. It also functions to convert folate, another B vitamin, to its active form. Deficiencies of vitamin B-12 are rather rare, except in older adults with poor absorption and in strict vegans and vegetarians who avoid ingesting animal products, the richest food sources of the vitamin.
Sources
Good food sources of vitamin B-12 include animal products such as meat, fish, poultry, eggs, milk and dairy products. Fortified breakfast cereals are another important source. According to Mayoclinic.com, a single day's supply of vitamin B-12 could come from eating a chicken breast and a hard-boiled egg, plus 1 cup of plain low-fat yogurt or 1 cup milk plus 1 cup of raisin bran cereal.
Functions
Vitamin B-12 maintains the protective covering surrounding nerve fibers. With insufficient intakes, nerve damage can result which leads to impaired muscle and nerve function. Numbness and tingling of the arms and legs can occur, often accompanied by difficulty walking, memory loss and mood alterations.Vitamin B-12 and folate actually depend upon each other for proper functioning. When vitamin B-12 intakes are low, folate does not assist in making new blood cells. This means large, immature red blood cells develop, which can actually be a sign of either folate or B-12 deficiency.
Intrinsic Factor
Absorption of vitamin B-12 is dependent upon a compound called intrinsic factor, which is manufactured in the stomach. Intrinsic factor binds to the available B-12, and together they are absorbed from the small intestine into the bloodstream. Normally adults over 50 years of age begin to lose the ability to make intrinsic factor, which reduces their ability to absorb vitamin B-12. Sometimes supplemental B-12 must be given by injection in order to circumvent the digestive system.
Deficiency
Vitamin B-12 deficiency is called pernicious anemia, and individuals most at risk for it include older adults and strict vegans and vegetarians. Estimated deficiency incidence in adults over 60 years old is ten to fifteen percent. Body stores are normally sufficient for five years, so overt symptoms of a poor intake will not be visible immediately. Supplementation at or below the Recommended Dietary Allowance of 2.4 mcg/day is seldom problematic, but be sure and consult your physician or registered dietitian if you are at high risk for a vitamin B-12 deficiency.
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