NUTR100 Lecture Notes - Lecture 13: Vitamin A Deficiency, Alpha-Carotene, Retinoid
13 Jun 2018
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Chapter 9: Fat Soluble Vitamins
- Vitamins ADEK
- require bile and dietary fat for absorption
- once absorbed, they are transported with fats through the lymphatic system in
chylomicrons
- can be stored in body fat, intakes can vary without a risk of deficiency as long as there is
average intakes over time
- they are not easily secreted, increases risk of toxicity with high intakes from
supplements
- still see Vit A and D deficiencies in developing world
- Vitamin A
o Preformed Vit A
▪ From animal products and supplements
▪ Retinoids (retinol, retinal, retinoic acid)
▪ Efficiently abosorbed
o Precursor form from some plants
▪ Carotenoids (beta-carotene(most potent, dark orange fruits and
vegetables) alpha carotene(carrots), beta crytoxanthin)
▪ Less efficient absorption
▪ Some converted to retinoids in intestinal cells
o Plays key role in vision, especially night,
o Gene expression to control cell, differentiation/growth, maintenance of
epithelial tissue, skin lining of eyes, lungs etc
o Light strikes rhodopsin(opsin and retinal), after cycle vitamin A combines with
retinal to form rhodopsin again
▪ Night blindness: first and most curable form of Vit A deficiency
o Vitamin A and gene expression
▪ Vitamin A combine with protein receptor, goes to regulatory region,
combines with mRNA transcription
• Turning on or off of gene expression can increase or decrease
protein creation b
o Plant and animal foods good form of Vitamin A
o Vitamin A deficiency
▪ Affects where protein and fat intake is low
▪ Epithelial tissues become keratinized
▪ Hard dry surface promotes infection
▪ Reduces immune function
▪ Poor child growth
• Lack of development of heart, circulatory, nervous, respiratory,
and skeletal systems
• Crooked teeth and poor dental health
o Toxicity: impossible to develop when ingested through food
▪ Carotenoidosis(orange skin) is not toxicity
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