vitamin a. definition vitamin a is a generic term for a large number of related compounds retinol...

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&parasitedisease&parasite

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)