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Vitamin A
Chief functions
 Generates pigments necessary for proper working of the retina to maintain good vision,
especially in dim light
 Enhances integrity of immune system
 Is essential in reproduction (during pregnancy and lactation for hormone synthesis)
 Helps form and maintain healthy:
– Skin
– Cornea
– Mucous membranes
– Skeletal and soft tissues
 Develops and maintains:
– Epithelial tissue
– Reproduction, digestion, and urinary tracts
– Lining of lungs
 Development and maintenance of the body’s barriers to infection:
– Skin
– Lungs
– Lining of mouth and throat
 Helps promote normal bone development
 Influences tooth formation
Possible benefits
 Functions as an antioxidant
 Anticancer:
– May reduce the risk of developing cancer of breast, stomach, cervix, and lungs by
maintaining healthy epithelial tissues or discouraging formation of abnormal cells (research
is mixed)
 Immunity:
– May increase resistance to infection in children
Deficiency symptoms
 Keratinization of tissues:
– Skin
– Cornea
– Respiratory lining
– Gastrointestinal tract lining
 Frequent infections of the:
– Respiratory and digestive system
– Bladder
– Vagina
 Xerophthalmia, leading to blindness and night blindness
 Kidney stones
 Microcytic anemia
 Impaired bone growth
Toxicity symptoms
 Diplopia
 Alopecia
 Bone abnormalities
 Joint pain
 Growth retardation
 Dry skin
 Rashes
 Dryness of mucous membranes
 Desquamation
 Skin may turn yellow
 Abnormal development of fetus in pregnant woman
 High incidence of spontaneous abortions and birth defects
 Nausea and vomiting
 Loss of appetite
 Headaches
 Abdominal discomfort
 Liver damage
 Liver and spleen enlargement
Stability
 Can withstand normal cooking temperatures
 Can withstand freezing and canning
 Rapidly deteriorates when foods dry out
 Rancidity destroys vitamin
 Destroyed by ultraviolet light and drying
Nutrient-nutrient reactions and absorption
 Vitamin A function is enhanced by the amount of vitamin E in the body
 An adequate intake of zinc is necessary for the proper use and transportation of vitamin A in
the body
 Retinol (active form of vitamin A) is more efficiently absorbed than most carotenoids
(precursors to vitamin A), 79% to 90% vs 20% to 50%
 As the amount of beta-carotene ingested increases, the efficiency of absorption decreases:
– The body stops converting beta-carotene into active vitamin A to avoid toxicity
 A small amount of dietary fat in the intestine is required for absorption:
– Any intestinal disorder that alters dietary absorption also will alter the absorption of
vitamin A
DRI
0-0.5 year
0.5-1 year
1-3 years
4-8 years
mcg
400
500
300
400
IU
2000
2500
1500
2000
Tolerable Upper Limits
600 mcg
600 mcg
600 mcg
900 mcg
9-13 years
600
3000
1700 mcg
Men >14 years
900
4500
3000 mcg
Women >14 years 700
3500
3000 mcg
Pregnancy
770
3850
3000 mcg
Lactating
1300 6500
3000 mcg
DRI=Dietary Reference Intakes, mcg=microgram, IU=international unit
Dietary sources of retinol (active form of vitamin A)
 Butter and margarine
 Cheese
 Cream
 Eggs
 Fish-liver oil
 Fortified milk
 Liver
Dietary sources of beta-carotene (precursor to vitamin A, converted in the
body)
 Apricots
 Broccoli
 Cantaloupe
 Carrots
 Dark-green leafy vegetables
 Deep-orange fruits and vegetables
 Pumpkin
 Spinach
 Sweet potatoes
 Winter squash
Groups at highest risk for deficiency
 Individuals with an inadequate intake of vitamin A
 Infants and young children in developing countries
 People who have cystic fibrosis
 Pregnant women in developing countries
 Premature infants
Other facts
 Vitamin A is the name of a group of fat-soluble retinoids, including:
– Retinol
– Retinal
– Retinoic acid
– Retinyl esters
 The most common precursor to vitamin A is beta-carotene (orange in color)
 The most active form of vitamin A is retinol (yellow)
 Beta-carotene is one of many carotenoids (other carotenoids have one-half the vitamin A
activity of beta-carotene)
 Carotenoids are not efficiently absorbed when taken in high doses, so they cannot become
toxic
 Toxicity occurs with large doses of retinol
 The vitamin A content of foods is measured as retinol activity equivalents (RAEs)
 1 RAE=3.33 IU of vitamin A
 1 RAE=12 mcg of beta-carotene from food
 1 RAE=1 mcg of retinol
 Example of conversions from IU RAE and retinol: 5000 IU vitamin A=1500 mcg retinol
 Guidelines are based on 1 RAE=5 IU, because it is assumed that more than one-half of vitamin
A intake will come from beta-carotene
 The need for vitamin A will increase with increasing body size and weight
 Children should not take a supplement, unless authorized by a doctor
 No DRI exists for beta-carotene:
– The best recommended amount is 5 to 6 milligrams
References and recommended readings
Dietary Reference Intakes: vitamins. Institute of Medicine of the National Academies Web site.
http://www.iom.edu/Global/News%20Announcements/~/media/474B28C39EA34C43A60A6D4
2CCE07427.ashx. Accessed October 8, 2013.
Dietary supplement fact sheet: vitamin A. National Institutes of Health, Office of Dietary
Supplements Web site. http://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/. Accessed
February 5, 2013.
Mahan LK, Escott-Stump S, Raymond JL. Krause’s Food and the Nutrition Care Process. 13th
ed. St Louis, MO: Elsevier Saunders; 2012.
Review Date 10/13
G-0755