Vitamin A Deficiency

Breif review on chemistry, physiology, Nutritional sources, Deficiency states and toxicity of Vitamin A.....Enjoy it !

1. Nutrition Vitamin A Deficiency By Wendwesen.A . Oct 10-2016 1

2. Definition Vitamin A is the name given to a group of related compounds that include retinol , retinal , and retinoic acid Have similar biologic activities Vitamin A , in the strictest sense, refers to retinol Retinoic acid is its active form 2

3. Sources Sources of vitamin A can be classified as 1. Preformed vitamin A sources: C ontains active vit A L iver , fish, eggs, milk, and butter 3

4. 2. ß-Carotene containing sources: Called pro-vitamin A carotenoids It is important compound in the food Has provitamin A activity and efficiently converted to retinol Yellow and leafy green vegetables such as carrots, squash, and spinach Cont’d... 4

5. Absorption and Storage Vitamin A is a fat-soluble vitamin Absorption requires bile Retinol and β-carotene are absorbed in the intestine 90% of the body's vitamin A reserves are stored in the liver called ITO cells Storage lasts at least 6 months Retinol is transport form & retinol ester is the storage form 5

6. Physiologic roles of vitanim A Maintenance of normal vision Retinaldehyde is the essential form of vitamin A that is required for normal vision The visual process involves four forms of vitamin A containing pigments: Rhodopsin in the rods , the most light-sensitive pigment 3 iodopsins in cone cells  each responsive to specific colors in bright light 6

7. 2. Cell growth and differentiation Vitamin A is important in differentiation of mucus -secreting epithelium W hen deficient, the epithelium undergoes squamous metaplasia differentiating into a keratinizing epithelium Cont’d... 7

8. Cont’d... 8 3. Host resistance to infections Maintain the integrity of the epithelium of the gut Boots the immune system Vitamin A supplementation can reduce morbidity and mortality from some forms of diarrhea , and measles Infections may reduce the bioavailability of vitamin A B y inhibiting retinol binding protein synthesis in the liver

9. Dietary supplements reduce mortality by 20% to 30% Retinoids are used clinically for the treatment of skin disorders such as severe acne and certain forms of psoriasis acute promyelocytic leukemia ! Cont’d... 9

10. Deficiency C auses of vitamin A deficiency can be: Chronic dietary deficiency, or Secondary deficiencies: malabsorptions , Deficiency states include: Ocular manifestatons The most common clinical presentation Ocular manifestations f vitamin A is called Xerophthalmia Night blindness is earliest manifestation of vit A deficiency Graded accordingly by WHO 10

11. Cont’d... 11

12. Xerophthalmia referred to as dry eye Xerosis conjunctivae there is dryness of the conjunctiva as the normal lacrimal and mucus-secreting epithelium is replaced by keratinized epithelium 12 Cont’d...

13. Bitot spots build up of keratin debris in small opaque plaques Keratomalacia erosion of the roughened corneal surface with softening and destruction of the cornea 13 Cont’d...

14. 2. Respiratory tract Loss of the mucociliary epithelium of the airways predisposes to secondary pulmonary infections , 3. Urinary system D esquamation of keratin debris in the urinary tract predisposes to renal and urinary bladder stones Cont’d... 14

15. 4. Dermatologic Hyperplasia and hyperkeratinization of the epidermis Plugs the ducts of the adnexal glands may produce follicular or papular dermatosis Cont’d... 15

16. Toxicity 16 Do you know that hypervitaminosis A can mimic brain Tumor? F irst noted in Arctic explorers who ate polar bear liver 150 mg in adults or 100 mg in children can induce toxic symptoms The symptoms of acute vitamin A toxicity include: headache , dizziness, vomiting, stupor, and blurred vision