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Vitamin Deficiency Disorders

Abdelaziz Elamin MD, PhD, FRCPCH Professor of Child Health College of Medicine Sultan Qaboos University Muscat, Oman azizmin@hotmail.com. Vitamin Deficiency Disorders. BACKGROUND. Vitamins are organic substances that are essential for several enzymatic functions in human metabolism.

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Vitamin Deficiency Disorders

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  1. Abdelaziz Elamin MD, PhD, FRCPCH Professor of Child Health College of Medicine Sultan Qaboos University Muscat, Oman azizmin@hotmail.com Vitamin Deficiency Disorders

  2. BACKGROUND • Vitamins are organic substances that are essential for several enzymatic functions in human metabolism • Thiamine was discovered in 1912 & was thought to be a vital amine compound & thus the term vitamin was invented

  3. VITAMINS • Vitamins are classified according to solubility into fat soluble & water soluble. • 13 vitamins are known, 4 fat soluble (KEDA) & 9 water soluble (C, Folate & the B group).

  4. VITAMIN A • Vitamin A is a generic term for many related compounds. • Retinol (alcohol), Retinal (aldehyde) are often called preformed vitamin A. Retinal can be converted by the body to retinoic acid which is known to affect gene transcription. • Body can convert b-carotene to retinol, thus called provitamin A.

  5. FUNCTIONS • Vision:integrity of eye & formation of rodopsin necessary for dark adaptation. • Regulation of gene expression: vital to cell differentiation & physiologic processes • Immunity: important for activation of T lymphocyte, maturation of WBC & integrity of physiological barrier. • Growth & development

  6. Nutrient Interactions • Zinc deficiency interfere with vitamin A metabolism in several ways: • It decreases the synthesis of retinol binding protein, which transports retinol to tissues. • It decreases the activity of the enzyme retinyl palmitate, which is necessary for release of retinol from the liver. • Zn is needed for the enzyme that convert retinol into retinal.

  7. Nutrient Interactions/2 • Iron & vitamin A. • Vitamin A deficiency may exacerbate IDF • Vitamin A supplementation improves iron status among children & pregnant women. • Combining vitamin A with iron controls IDA more quickly & effectively than using iron alone.

  8. VITAMIN A UNITS • 1 mg of retinol = 6 mg of b-carotene. • 3 mg of retinol = 10 international units of vitamin A. • 100 mg carrots contain 10 mg of b-carotene.

  9. Recommended Allowance

  10. RICH DIETARY SOURCES

  11. Vitamin A deficiency • Deficiency of vitamin A leads to: • Night blindness & xerophthalmia • Growth retardation • Acquired immune deficiency • Keritinization of epithelia in RT, GIT & UT with increased risk of RTI, malabsorption & UTI.

  12. THERAPEUTIC USES • Vitamin A deficiency • Boosting immunity of infants • Skin disorders • Acute promyelotic leukemia • Cancer prevention (lung & breast)

  13. TOXICITY • Vitamin A in excess leads to: • Dermatitis with xanthosis cutis • Hepatosplenomegaly • Bone pain & increased risk of fracture • Pseudotumor Cerebri

  14. VITAMIN D • Vitamin D comprises a group of sterols; the most important of which are cholecalciferol (vitamin D3) & ergosterol (vitamin D2). • Humans & animal utilize only vitamin D3 & they can produce it inside their bodies from cholesterol. • Cholesterol is converted to 7-dehydro-cholesterol (7DC), which is a precursor of vitamin D3.

  15. VITAMIN D • Exposure to the ultraviolet rays in the sunlight convert 7DC to cholecalciferol. • Vitamin D3 is metabolically inactive until it is hydroxylated in the kidney & the liver to the active form 1,25 Dihydroxycholecalciferol. • 1,25 DHC acts as a hormone rather than a vitamin endocrine & paracrine properties.

  16. FUNCTIONS • Calcium metabolism: vitamin D enhances ca absorption in the gut & renal tubules. • Cell differentiation: particularly of collagen & skin epithelium • Immunity: important for Cell Mediated Immunity & coordination of the immune response.

  17. Vitamin D deficiency • Deficiency of vitamin D leads to: • Rickets in small children. • Osteomalacia • Osteoporosis

  18. GROUPS AT RISK • Infants • Elderly • Dark skinned • Covered women • Kidney failure patients • Patients with chronic liver disease • Fat malabsorption disorders • Genetic types of rickets • Patients on anticonvulsant drugs

  19. Sources of Vitamin D • Sunlight is the most important source • Fish liver oil • Fish & sea food (herring & salmon) • Eggs • Plants do not contain vitamin D3

  20. THERAPEUTIC USES • Rickets & Osteomalacia • Osteoporosis • Psoriasis • Cancer prevention (prostate & colorectal) • Autoimmune diseases

  21. TOXICITY • Hypervitaminosis D • causes hypercalcemia,which manifest as: • Nausea & vomiting • Excessive thirst & polyuria • Severe itching • Joint & muscle pains • Disorientation & coma.

  22. RICKETS

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