Vitamin A

Question 1

What is vitamin A?

Answer 1

A group of fat-soluble retinoids, including retinol, retinal, retinoic acid, and retinyl esters.

Question 2

What are the two groups of vitamin A in the diet?

Answer 2

Preformed vitamin A (retinoids) and provitamin A carotenoids.

Question 3

What is the most potent precursor of vitamin A?

Answer 3

β-Carotene.

Question 4

Name two other provitamin A carotenoids.

Answer 4

• α-Carotene
• β-Cryptoxanthin

Question 5

What is required for vitamin A absorption in the body?

Answer 5

Bile salts.

Question 6

What is the absorption percentage of retinol and β-carotene from dietary sources?

Answer 6

• Retinol: 70-90%
• β-Carotene: 20-50%

Question 7

Where is most vitamin A stored in the body?

Answer 7

Approximately 90% is stored in the liver, primarily in stellate cells as retinyl esters.

Question 8

How is vitamin A transported in the body?

Answer 8

It is released into circulation bound to prealbumin (transthyretin) and retinol-binding protein (RBP).

Question 9

What happens when the body’s vitamin A stores are depleted?

Answer 9

Vitamin A deficiency occurs, impairing physiological functions even before clinical eye signs appear.

Question 10

What is the recommended daily intake of vitamin A for adults?

Answer 10

• Males (>18 years): 900 μg RAE/day
• Females (>18 years): 700 μg RAE/day
• Pregnant women: 770 μg RAE/day
• Lactating women: 1300 μg RAE/day

Question 11

What is Retinol Activity Equivalent (RAE)?

Answer 11

The amount of vitamin A providing activity equivalent to:
* 1 μg all-trans-retinol
* 6 μg β-carotene
* 12 μg other provitamin A carotenoids

Question 12

What are rich food sources of vitamin A?

Answer 12

• Plant: Carrots, dark green leafy vegetables.
• Animal: Liver, cod liver oil.

Question 13

What is the leading cause of preventable childhood blindness?

Answer 13

Vitamin A deficiency (VAD).

Question 14

How does VAD affect pregnant women?

Answer 14

It increases all-cause mortality and adversely affects pregnancy outcomes.

Question 15

What percentage of women of childbearing age in the UAE have vitamin A deficiency?

Answer 15

3%, indicating a mild public health problem.

Question 16

Which age group is most vulnerable to VAD?

Answer 16

Preschool-age children.

Question 17

Why are preschool children more vulnerable to VAD?

Answer 17

• High requirements for rapid growth
• Transition from breastfeeding to other diets
• Increased frequency of infections

Question 18

Which gender is more affected by night blindness and Bitot’s spots?

Answer 18

Males (1.2-10 times more than females).

Question 19

Why is VAD common in rice-dependent communities?

Answer 19

Rice is low in vitamin A, and such communities have limited dietary diversity.

Question 20

What physiological stages increase the risk of VAD in women?

Answer 20

• Pregnancy (especially last trimester)
• Lactation

Question 21

Name some conditions associated with secondary vitamin A deficiency.

Answer 21

• Liver diseases
• Protein-energy malnutrition (PEM)
• Malabsorption (e.g., cystic fibrosis, chronic diarrhea, bile duct obstruction)

Question 22

What are the early manifestations of VAD?

Answer 22

Increased rates of infections due to compromised epithelial barriers and immune system.

Question 23

What is xerophthalmia?

Answer 23

A term that includes all ocular manifestations of vitamin A deficiency.

Question 24

List the stages of xerophthalmia.

Answer 24

• Night blindness
• Conjunctival xerosis
• Bitot’s spots
• Corneal xerosis
• Corneal ulcers and keratomalacia

Question 25

How can early stages of xerophthalmia be treated?

Answer 25

Vitamin A supplementation can lead to complete recovery.

Question 26

What are the risk factors for VAD?

Answer 26

* Age (preschool children) * Gender (more common in males) * Pregnancy and lactation * Poor diet and breastfeeding practices * Infections and intestinal parasites * Low socio-economic status

Question 27

How does VAD interact with infectious diseases?

Answer 27

VAD increases infection severity, and infections reduce vitamin A intake and accelerate its loss, worsening deficiency.

Question 28

What is the relationship between VAD and protein-energy malnutrition (PEM)?

Answer 28

VAD often coexists with PEM and delays recovery from corneal xerophthalmia.

Question 29

How does seasonality affect VAD?

Answer 29

Vitamin A and carotene availability fluctuate, with deficiencies emerging during summer diarrhea seasons.

Question 30

How can xerophthalmia be prevented?

Answer 30

Through adequate maternal vitamin A storage, prolonged breastfeeding, and improved dietary intake.

Question 31

Which form of vitamin A is predominantly stored in the liver?

Answer 31

Retinyl esters.

Question 32

What percentage of vitamin A in the liver is stored in stellate cells?

Answer 32

90-95%.

Question 33

Which protein helps vitamin A circulate in the body?

Answer 33

Retinol-binding protein (RBP).

Question 34

What is the conversion factor of IU Retinol to RAE?

Answer 34

0.3 μg RAE.

Question 35

What is the most common cause of primary vitamin A deficiency?

Answer 35

Dietary inadequacy.

Question 36

Which disorder interferes with vitamin A absorption by impairing bile acid production?

Answer 36

Bile acid insufficiency.

Question 37

What is the term for white plaques on the conjunctiva due to VAD?

Answer 37

Bitot’s spots.

Question 38

In which country is VAD considered a mild public health issue based on serum retinol levels?

Answer 38

UAE.

Question 39

Which physiological condition has the highest demand for vitamin A?

Answer 39

Lactation.

Question 40

Which organ, apart from the liver, stores small amounts of vitamin A?

Answer 40

Kidney.

Question 41

What is the prevalence of VAD-related night blindness in preschool-age children globally?

Answer 41

45 countries.

Question 42

Which intestinal parasite increases the risk of vitamin A deficiency?

Answer 42

Giardiasis.

Question 43

What stage of xerophthalmia is characterized by granular dryness of the cornea?

Answer 43

Corneal xerosis.

Question 44

What is the primary risk factor for xerophthalmia in children?

Answer 44

Early cessation of breastfeeding.

Question 45

Which communities are most prone to VAD due to dietary practices?

Answer 45

Rice-dependent communities.

Question 46

Which carotenoid has the highest vitamin A activity?

Answer 46

β-Carotene.

Question 47

What is the estimated absorption percentage of β-carotene from dietary sources?

Answer 47

20-50%.

Question 48

What conditions involves fat-soluble vitamin malabsorption, including vitamin A?

Answer 48

Pancreatic insufficiency, cystic fibrosis, diarrhea, bile duct obstruction, giardiasis, cirrhosis, sprue

Question 49

What term is used to describe all ocular manifestations of vitamin A deficiency?

Answer 49

Xerophthalmia.

Question 50

Which vitamin A deficiency stage causes reduced ability to see in dim light?

Answer 50

Night blindness.

Question 51

What percentage of vitamin A is stored in fat depots, lungs, and kidneys?

Answer 51

10%.

Question 52

What is the primary dietary source of preformed vitamin A?

Answer 52

Animal foods.

Question 53

Which socio-economic factor correlates closely with VAD?

Answer 53

Economic deprivation.

Question 54

What is the primary factor responsible for vitamin A deficiency in 'rice-dependent' communities?

Answer 54

Low dietary diversity.

Question 55

What is the primary impact of VAD on epithelial barriers?

Answer 55

Compromised integrity leading to increased infection rates.