vitamins

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Vitamin A

Vitamins

Vitamin A

  • Found in animal foods and converted from beta-carotene in plant foods.
  • Required for vision, gene expression, reproduction, embryonic development, red blood cell production, and immune function.
  • Prescription vitamin A derivatives are used to treat skin conditions (acne) and retinitis pigmentosa (genetic eye disease).
  • Deficiency is rare in Canada, but common in developing countries due to malnutrition. It causes night blindness, dry eyes and skin, and impaired growth.
  • Drugs that deplete vitamin A: cholestyramine, colestipol, mineral oil, and neomycin.
  • Supplements should be avoided by those at risk of lung cancer (smokers) or liver toxicity (alcoholics, liver disease).
  • Doses greater than 10,000 IU daily should be avoided by pregnant women due to the risk of birth defects. Most prenatal vitamins provide 5,000 IU.
  • Doses greater than 5,000 IU may increase risk of osteoporosis.
  • Supplements of vitamin A beyond what is provided in a multivitamin are not recommended due to risk of toxicity. To avoid this risk, choose a multivitamin that contains beta-carotene, which is converted to vitamin A in the liver, but is not associated with health risks.

  • Food Sources : Liver, dairy products, and oily fi sh (Beta-carotene is found in orange and green vegetables and fruit)
  • Adequate Intake : (mcg/day)
    Men = 900
    Women = 700
    Pregnancy = 770
    Lactation = 1,300
  • Upper Limit : (mcg/day)
    Men = 3,000
    Women = 3,000
    Pregnancy = 3,000
    Lactation = 3,000
    Note: 1 mcg = 3.33 IU
  • Side Effects : Liver toxicity and birth defects (associated with vitamin A, not beta-carotene)


  • Vitamin B6 Pyridoxine
    Vitamin E
    Vitamin B12 Cobalamin
    Biotin
    Vitamin B3 Niacin
    Vitamin B2 Ribofl avin
    Folate Folic Acid
    Vitamin B5 Pantothenic Acid
    Vitamin K
    Vitamin B1 Thiamine
    Vitamin C Ascorbic Acid
    Vitamin A
    More ...

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