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)