Vitamin A

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Vitamin A
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Three Active Forms

• Retinol an alcohol, from animal tissues
• Retinal an aldehyde, the active form for vision
  and can be converted from retinol
• Retinoic Acid cannot be utilized in the body
  where alcohol or aldehyde form is required, it is
  used by epithelial cells.

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Vitamin A

• Readily undergoes oxidation when exposed to air.
• Vitamin E helps prevent this oxidation

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Carotenoid Pigments

• Present in yellow, red, orange and green
  vegetables
• Contained in some vegetable oils
• Animal meats contain A
• Fish liver oil best source.

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Retinols

• Stored in liver
• Transported on a binding protein
• Functions of Vitamin A are clear only in regards
  to vision.
• Other important functions still need to be
  elucidated

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Functions

• Visual cycle alcohol and aldehyde forms only
• Growth
• Reproduction
• Maintain epithelial cells

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Deficiency

• Night blindness is earliest sign of Vitamin A
  deficiency.
• Question patients how they do in a dark room,
  i.e. when going to a movie, if you enter after it
  has started, can you quickly find a seat or
  must you wait until your eyes adjust? Wait
  amount of deficiency.

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Toxicity

• Toxicity is very overrated.
• Many more people die from deficiency.
• Still, it is toxic in large amounts, and
  especially in pregnancy and for young children.
• lt 5000 I.U. for children
• lt10,000 I.U. for adults

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Storage

• Typically there is about a 9 month store of
  Vitamin A in the liver.
• Prolonged deficiency leads to an irreversible
  loss in the number of rods and cones.
• Prolonged deficiency results in xeropthalmia (a
  dryness and unwettability of the bulbar
  conjunctiva).
• Ultimately causes blindness

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• Xeropthalmia is the leading cause of blindness in
  third world countries

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Extraocular

• Occurs in epithelium where columnar epithelia is
  replaced with thick layers of dry stratified
  epithelium.
• All external and internal skin surfaces are
  affected (skin, lungs, stomach, intestines,
  respiratory passages, urinary tract)

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Early Skin Sign

• A heaping up of hyperkeratinized skin around hair
  follicles, especially on the outer aspects of the
  upper arms and thighs.
• This is actually a very common finding,
  especially in young women.
• Essential fatty acid deficiency plays into this
  as well.

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Bone Growth

• Vitamin A has a role in bone growth. A helps
  remodeling of old bone into longer and bigger
  bones in children.
• In the jaw, Vitamin A aids in normal tooth spacing

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Toxicity

• Can happen only with over supplementation, or
  drinking carrot juice in large quantities.
• Deaths have been due to eating polar bear liver.
  Wild animals will NOT eat the liver of the polar
  bear

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Hypercarotenosis

• Excessive supplementation or drinking too much
  carrot juice will cause carotenemia.
• Yellow or orange discoloration of skin first
  noticed in the nasolabial folks, forehead,
  axillae, groin, palms and soles.
• As opposed to jaundice the sclera is NOT
  involved.

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Beta Carotene

• Supplemental forms should include some Vitamin A
  and some beta carotene. Beta carotene is the
  natural precursor to A and body will not
  convert it if not needed.
• This measure will help reduce toxicity, but large
  amounts of beta carotene eventually will cause
  carotenemia as well.

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Improvements Noted In

• Numbers of and severity of URIs
• Numbers of and severity of UTIs
• Symptoms of IBS
• Vaginal dryness
• Various skin disorders
• (If the skin or a mucous membrane is involved
  Vitamin A can help)