Vitamin Deficiency Disorders
By:Abdelaziz Elamin, MD, PhD, FRCPCH
Professor of Child Health, College of Medicine
Sultan Qaboos University, Muscat, Oman
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
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).
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.
FUNCTIONS
* Vision: integrity of eye & formation of rodopsin necessary for dark adaptation.
* Regulation of gene expression: vital to cell differentiation & physiologic processes
* Growth & development
* Immunity: important for activation of T lymphocyte, maturation of WBC & integrity of physiological barrier.
Nutrient Interactions
* Zinc deficiency interfere with vitamin A metabolism in several ways:
o It decreases the synthesis of retinol binding protein, which transports retinol to tissues.
o It decreases the activity of the enzyme retinyl palmitate, which is necessary for release of retinol from the liver.
o Zn is needed for the enzyme that convert retinol into retinal.
* Iron & vitamin A.
o Vitamin A deficiency may exacerbate IDF
o Vitamin A supplementation improves iron status among children & pregnant women.
o Combining vitamin A with iron controls IDA more quickly & effectively than using iron alone.
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.
Recommended Allowance
Papaya
Fish & meet
Apricot
Milk & cheese
Spinach
Butter
Cantaloupe
Egg
Carrots
Liver & kidney
Sweet potato
Cod liver oil
Plant Foods
Animal Foods
RICH DIETARY SOURCES
Vitamin A deficiency
* Deficiency of vitamin A leads to:
o Night blindness & xerophthalmia
o Growth retardation
o Acquired immune deficiency
o Keritinization of epithelia in RT, GIT & UT with increased risk of RTI, malabsorption & UTI.
THERAPEUTIC USES
* Vitamin A deficiency
* Boosting immunity of infants
* Skin disorders
* Acute promyelotic leukemia
* Cancer prevention (lung & breast)
TOXICITY
* Vitamin A in excess leads to:
o Dermatitis with xanthosis cutis
o Hepatosplenomegaly
o Bone pain & increased risk of fracture
o Pseudotumor Cerebri
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.
* 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.
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.
Vitamin D deficiency
* Deficiency of vitamin D leads to:
o Rickets in small children.
o Osteomalacia
o Osteoporosis
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
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
THERAPEUTIC USES
* Rickets & Osteomalacia
* Osteoporosis
* Psoriasis
* Cancer prevention (prostate & colorectal)
* Autoimmune diseases
TOXICITY
* Hypervitaminosis D
causes hypercalcemia, which manifest as:
o Nausea & vomiting
o Excessive thirst & polyuria
o Severe itching
o Joint & muscle pains
o Disorientation & coma.
RICKETS
Vitamin Deficiency Disorders.ppt
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