vitamin a. definition vitamin a is a generic term for a large number of related compounds retinol...
TRANSCRIPT
Vitamin A Vitamin A
DefinitionDefinition
Vitamin A is a generic term for a Vitamin A is a generic term for a large number of related compounds large number of related compounds
• Retinol (an alcohol) Retinol (an alcohol) • Retinal (an aldehyde) Retinal (an aldehyde) • Retinoic acid Retinoic acid • Carotenoids Carotenoids
FunctionFunction
VisionVision Regulation of gene expressionRegulation of gene expression Maintenance of epithelial tissueMaintenance of epithelial tissue ImmunityImmunity Growth and developmentGrowth and development Red blood cell productionRed blood cell production Prevention of cancerPrevention of cancer
Recommended Dietary Allowance (RDA) for Vitamin A as Preformed Vitamin A (Retinol)
Life Stage Age Males: mcg/day (IU/day)
Females: mcg/day (IU/day)
Infants 0-6 months 400 (1333 IU) 400 (1333 IU)
Infants 7-12 months 500 (1667 IU) 500 (1667 IU)
Children 1-3 years 300 (1000 IU) 300 (1000 IU)
Children 4-8 years 400 (1333 IU) 400 (1333 IU)
Children 9-13 years 600 (2000 IU) 600 (2000 IU)
Adolescents 14-18 years 900 (3000 IU) 700 (2333 IU)
Adults 19 years and
older 900 (3000 IU) 700 (2333 IU)
Pregnancy 18 years and
younger - 750 (2500 IU)
Pregnancy 19-years and
older- 770 (2567 IU)
Breastfeeding 18 years and
younger - 1,200 (4000 IU)
Breastfeeding 19-years and
older - 1,300 (4333 I
Good dietary sources of vitamin AGood dietary sources of vitamin A
Best sources include:Best sources include:– beef liverbeef liver– carrots (as beta-carotene)carrots (as beta-carotene)– mustard greens (as beta-carotene)mustard greens (as beta-carotene)– eggseggs– apricots (as beta-carotene)apricots (as beta-carotene)
Note that beta-carotene is much less Note that beta-carotene is much less toxic in higher doses than is the toxic in higher doses than is the preformed animal forms of vitamin Apreformed animal forms of vitamin A
Food ServingVitamin A,
RAE Vitamin A, IU Retinol, mcg Retinol, IU
Cod liver oil 1 teaspoon 1,350 mcg 4,500 IU 1,350 mcg 4,500 IU
Fortified breakfast cereals
1 serving 150-230 mcg 500-767 IU 150-230 mcg 500-767 IU
Egg 1 large 91 mcg 303 IU 89 mcg 296 IU
Butter 1 tablespoon 97 mcg 323 IU 95 mcg 317 IU
Whole milk1 cup (8 fl ounces)
68 mcg 227 IU 68 mcg 227 IU
2% fat milk (vitamin A added)
1 cup (8 fl ounces)
134 mcg 447 IU 134 mcg 447 IU
Nonfat milk (vitamin A added)
1 cup (8 fl ounces)
149 mcg 500 IU 149 mcg 500 IU
Sweet potato1/2 cup, mashed
959 mcg 3,196 IU 0 0
Carrot (raw)1/2 cup, chopped
385 mcg 1,283 IU 0 0
Cantaloupe1/2 medium melon
466 mcg 1,555 IU 0 0
Spinach1/2 cup, cooked
472 mcg 1,572 IU 0 0
Squash, butternut
1/2 cup, cooked
572 mcg 1,906 IU 0 0
Retinol activity equivalency (RAE) ratios for beta-carotene and other provitamin A carotenoids
Quantity ConsumedQuantity
Bioconverted to Retinol
RAE ratio
1 mcg of dietary or supplemental vitamin A
1 mcg of retinol* 1:1
2 mcg of supplemental beta-carotene
1 mcg of retinol 2:1
12 mcg of dietary beta-carotene
1 mcg of retinol 12:1
24 mcg of dietary alpha-carotene
1 mcg of retinol 24:1
24 mcg of dietary beta-cryptoxanthin
1 mcg of retinol 24:1
*One IU is equivalent to 0.3 mcg of retinol, and one mcg of retinol is equivalent to 3.33 IU of retinol.
vitamin A deficiencyvitamin A deficiency
SymptomsSymptoms• Dry, hard skinDry, hard skin• Dry cornea and eventual blindness Dry cornea and eventual blindness
((XerophthalmiaXerophthalmia))• Night blindnessNight blindness (insufficient retinal (insufficient retinal
for rhodopsin formation)for rhodopsin formation)• Impaired immune functionImpaired immune function• Deficiency also causes a decrease in Deficiency also causes a decrease in
appetite and poor growthappetite and poor growth
General_2000.shp0 - 1010 - 1919 - 2929 - 3838 - 48
Cause of deficiencyCause of deficiency
• Insufficent intake(poverty,low income,…)Insufficent intake(poverty,low income,…)• Lack of food sources of V.ALack of food sources of V.A• Low fat dietLow fat diet• Malabsorption(surgery,parasite,…)Malabsorption(surgery,parasite,…)• Increasedneed(pregnancy,breastfeeding,Increasedneed(pregnancy,breastfeeding,
…)…)• Insufficent Supplemental feedingInsufficent Supplemental feeding• Infectious diseaseInfectious disease
Deficiency in children:Deficiency in children:
• 250 millions preschool children have 250 millions preschool children have subclinical deficiencysubclinical deficiency
• The most incidencecause of blindness in The most incidencecause of blindness in developing countries(500000 children in developing countries(500000 children in year)year)
• If 1% children(2-6 years old)with night If 1% children(2-6 years old)with night blindness or 10% children (6 months-6 blindness or 10% children (6 months-6 years )had serum retinol below years )had serum retinol below 7%micromol/l that population had health 7%micromol/l that population had health problem.problem.
• Improve of V.A level in infant lead to Improve of V.A level in infant lead to decrease of 23% mortality decrease of 23% mortality
Control of VADDControl of VADD
1.Breastfeeding1.Breastfeeding
2.Supplementation2.Supplementation
3.Fortification3.Fortification
4.Food variety4.Food variety
5.Control of infectious 5.Control of infectious disease¶sitedisease¶site
Supplement in severeV.A.D Supplement in severeV.A.D populatinpopulatin
• Infant(<6months) 50000IUInfant(<6months) 50000IU(not fed breastmilk or their mothers not take V.A (not fed breastmilk or their mothers not take V.A
supplement)supplement)• Infant(6-12months ) 100000IUInfant(6-12months ) 100000IU(every 4-6 months)(every 4-6 months)• Children(>1 year) 200000IUChildren(>1 year) 200000IU(every 4-6 months)(every 4-6 months)• Children +1 mega dose Children +1 mega dose • (withmeaslse,diahrea,pneumonia& severe (withmeaslse,diahrea,pneumonia& severe
malnutrition)malnutrition)• Mothers +1 mega dose Mothers +1 mega dose • (during 8 week after delivery)(during 8 week after delivery)
Supplement in low V.A.D populatinSupplement in low V.A.D populatin
• Children(<2 years) 1500IU/dailyChildren(<2 years) 1500IU/daily
• Pregnancy 500IU/dailyPregnancy 500IU/daily(from4 months- delivery)(from4 months- delivery)
2500IU/weekly2500IU/weekly
ToxicityToxicity
Symptoms Symptoms • nausea, headache, fatigue, loss of nausea, headache, fatigue, loss of
appetite, dizziness, and dry skin, in appetite, dizziness, and dry skin, in pregnancy birth defects pregnancy birth defects
Signs of chronic toxicity Signs of chronic toxicity • dry itchy skin, loss of appetite, headache, dry itchy skin, loss of appetite, headache,
and bone and joint painand bone and joint pain
Severe hypervitaminosis A Severe hypervitaminosis A • liver damage, liver damage, hemorrhage, and coma , and coma
Tolerable Upper Level of Intake (UL) for Preformed Vitamin A (Retinol)
Age Group UL in mcg/day (IU/day)
Infants 0-12 months 600 (2,000 IU)
Children 1-3 years 600 (2,000 IU)
Children 4-8 years 900 (3,000 IU)
Children 9-13 years 1,700 (5,667 IU)
Adolescents 14-18 years 2,800 (9,333 IU)
Adults 19 years and older 3,000 (10,000 IU)