Vitamin B-12

Cyanocobalamin

Functions

  • Red blood cell formation
  • Involved in synthesis of nucleic acids
  • Fatty acid catabolism
  • Nervous system myelination (covering over nerves)
  • Reduction of glutathione

Deficiency

  • Pernicious anemia
  • Unsteady gait and dizziness
  • Chronic fatigue or drowsiness
  • Constipation
  • Depression, Irritability, or mood swings
  • Digestive disturbances
  • Liver enlargement
  • Hallucinations
  • Headaches
  • Nerve disorders
  • Spinal cord degeneration
  • Inflammation of tongue
  • Palpitations
  • Tinnitus

Characteristics

  • soluble in water or alcohol
  • unstable in hot alkaline or acid solutions

Good Sources

Vitamin B-12

Natural

  • beef, pork, chicken
  • liver, kidney
  • milk and dairy products
  • eggs
  • clams, oysters, king crab, herring, salmon, tuna
  • most of vitamin required by humans is synthesized by intestinal bacteria
Food Quantity mcg
Beef, lean braised flank 3 oz 2.81
Chicken 1/2 breast 0.29
Milk, non-fat 1 cup 0.93
Egg 1 large 0.50

Artificial

  • fortified cereals and soy products

Recommended Daily Allowances (RDA)

  • Males (11 yrs. and older)
    • 2.4 mcg
    • 3 mcg
  • Females (11 yrs. and older)
    • 2.4 mcg
    • 3 mcg
  • Pregnant females
    • 4 mcg
  • Lactating females
    • 5 mcg
  • Children
    • 2-5 mcg
  • Infants
    • 1-2 mcg
  • Varied values reflect different references

Tolerable Upper Intake Levels (UL)

  • Adults (19 to 50 yrs)
    • not yet determined
  • Generally considered non-toxic
  • Intakes above UL may lead to negative health consequences
    • Eg: Oversupply of B-12 works against Vitamin C concentrations in tissues

Supplementation

  • Not usually necessary
  • People who are on strict vegetarian diets may need supplementation.
    • some recommend 25-500 mcg daily
  • Some elderly people and those with certain food intolerances may be deficient in Vitamin B-12 because they lose their ability to absorb B-12 from foods.
    • In which case, parenteral vitamin B-12 can be prescribed by a health care professional.
  • Not required to be taken with other nutrients

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