Vitamin B12 (Cobalamin)

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 helps prevent anemia that makes people tired and weak. Involved in the metabolism of single-carbon fragments. Essential for biosynthesis of nucleic acids and nucleoproteins. Role in metabolism of nervous tissue. Involved with folate metabolism. Related to growth.

Vitamin B12 is synthesized by bacteria, but the vitamin produced from the microflora in the colon is not absorbed. Food of plant origin contain the vitamin only through contamination or bacterial synthesis. 

Slowly destroyed by acid, light and oxidation.

Dietary reference intakes of Vitamin B12

Infants 0.4-0.5 mcg/day

Children 0.9-1.8 mcg/day

Adolescents 2.4 mcg/day

Adults 2.4 mcg/day

Pregnant 2.6 mcg/day

Lactating 2.8 mcg/day

Vitamin B12 content of selected foods

Liver, beef, 3.5 oz (71 mcg)

Clams, canned, 3 oz (84 mcg)

Oysters, raw, 6 medium (16.6 mcg)

Crab, raw, 3 oz (10 mcg)

Tuna, canned in water, 3 oz (2.5 mcg)

Halibut, baked, ½ filet (2.2 mcg)

Cottage cheese, 1 cup (1.6 mcg)

Yogurt, 8 oz (1.1 mcg)

Symptoms of Vitamin B12 deficiency


Progressive neuropathy (numbness, tingling and burning of the feet, stiffness and generalized weakness of the legs)

A lemon-yellow tint to the skin

A smooth, beefy, red tongue

Neurologic disorders.

The best way to get the daily requirement of essential vitamins is to eat a balanced diet that contains a variety of foods.

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