word "vitamin" comes from the Latin word
vita, means "life".
are chemicals found in very small
amounts in foods.
“Vitamins have been defined as organic
compounds which are required in minute
amounts to maintain normal health of
Retinal (vitamin A aldehyde) :
• This is an aldehyde form obtained by the
oxidation of retinol.
• Retinal and retinol are interconvertible.
Retinoic acid (vitamin A acid) :
• produced by the oxidation of retinal.
• However, retinoic acid cannot give rise to the
formation of retinal or retinol.
Beta-Carotene (provitamin A) :
• Found in plant foods.
• lt is cleaved in the intestine to produce two
moles of retinal.
• ln humans, this conversion is inefficient, hence
beta-carotene possesses about one-sixth
vitamin A activity compared to that of retinol.
• Absorption: with help of bile salt in intestine
• Transport: via lymph with help of chylomicron
• Storage : liver in form of Retinyl palmitate
• Free retinol is highly active but toxic & therefore
transported in blood stream in combination with retinol
• Rhodopsin is congucated protein, light sensitive
pigment within rod and cone cells of the retina.
Rods are involved in dim light vision
Cones are responsible for bright light & colour vision
The colour vision is governed by colour sensitive
pigments porphyropsin (red), iodopsin
(green) and cyanopsin (blue).
Dietary Sources of Vitamin A
Cod liver oil
Men and women – 750-1000 μg.
Pregnancy and lactation – 1000 μg.
Infants – 350 μg.
Children – 400-600 μg.
Preschool children with decreased intake
Liver disease (limits storage)
The signs of vitamin A deficiency
Effect on reproductive
Effect on bone
Lack of vitamin A causes night blindness or inability to see
in dim light as a result of inadequate pigment in the retina.
• Conjunctiva become dry, thick and wrinkled
• Grayish white triangular spots in conjunctiva
• Infection leads to corneal ulceration and total
Skin and Epithelial cells:
Keratinization of GI, respiratory tracts
Degeneration of germinal epithelium- infertility
Symptoms and signs:
•Tenderness of long bones