NOTA SLAID

Vitamin A: plant sources

• Vitamin A also exist in the forms of provitamin

• e.g. ß-carotene (in plant)

• The yellow-orange-red provitamin carotenoids can yield
retinoids when metabolized in the body

• Although several hundred carotenoids exist in
foods naturally as antioxidants only few have
significant vitamin A activity

– Most important is ß-carotene (most active form)

• Provitamin cannot be synthesize by animal but
can convert it to vitamin A

• The amount of vitamin A available from
dietary carotenoids depends on how well
they are absorbed and how efficient they are
converted to retinol

– The conversion occurs in the intestinal mucosa cell



• Before preformed
vitamin A & carotenoids
can be absorbed

– proteases in stomach &
small intestine must
hydrolyzed proteins
which complexed with
these compounds

Retinol Equivalent (RE)

• According to FAO/WHO:

1 μg retinol = 1 RE
1 μg β-carotene = 0.167 μg RE, (1/6 μg )
1 μg other pro-vitamin A carotenoids = 0.084 μg RE, (1/12 μg)

RNI for Malaysia (2017)

Age group 0 – 5 months μg RE/day
Infant 6 – 11 months 375
400
Children 1 – 3 years 400
4 – 6 years 450
≥10 years 7 – 9 years 500
Pregnancy 600
Lactation 800
850

Food Sources (per 100 g)

Meat/ Poultry/Fish Vitamin A (μg RE/100g)
Chicken liver 16,000
Ox/ Beef liver 9,000
304
Hen egg, whole 208
Duck egg, whole 69
50
Duck, thigh 8
Chicken, thigh 8
Mackarel, Indian (kembong)
Mackarel, Spanish (Tenggiri)

Fruits Vitamin A (μg RE/100g)
Mango 214
Papaya 193
Watermelon 68
Kundang (kemoir) 55

Vegetables Vitamin A (μg RE/100g)
Cekur Manis (sweet leaf) 1620
1510
Red Capsicum 1210
Kesum (laksa leaf) 960
Maman (cleome gynandra) 835
700
Carrot
Tomato

Processed Foods Vitamin A (μg RE/100g)
Cornflakes 812
767
Malted milk powder 400
Full cream milk powder 200
117
Butter
Cheddar Cheese

Functions

• Main function

• required for vision

• Second main function

• In the maintenance of growth and epithelial cellular integrity and immune
function in the body

Role of Vitamin A in Vision

• Retinol plays an important part in the formation of rhodopsin,

• an important visual pigment, particularly for dim-light vision

• All-trans retinol is converted to retinaldehyde, summarized to the 11-
cis form and bound to opsin to form rhodopsin

• When there is insufficient
amount of retinol available,

• rhodopsin synthesis is
affected, and night blindness
may result

The Visual Cycle

Role in the maintenance of growth and epithelial
cellular integrity and immune function

• In vitamin A deficiency,

• the number of goblet cells are reduced in epithelial tissues,
• resulting in a reduction in mucous secretions with their antimicrobial

components.

• Cells lining protective tissue surfaces flatten and accumulate keratin
because they fail to regenerate and differentiate.

• All these changes result in

• diminished resistance to invasion by potentially pathogenic organisms.

• The immune system is also adversely affected by direct interference
with production of some types of protective secretion and cells.

Deficiency

• Most susceptible populations:

– Preschool children with low intake
– Urban poor
– Older adults
– Alcoholism
– Liver disease (limits storage)
– Fat malabsorption

Consequences of Deficiency

• Night blindness (Nyctalopia)

– due to functional failure of the retina in
regenerating rhodopsin

• Xerophthalmia

– Dryness of the conjunctiva

Xerophthalmia

• Followed by the build-up of keratin debris in
small opaque plaques (Bitot's spots)

Bitot’s spot Bitot’s spot

• And, eventually, erosion of the roughened
corneal surface with softening and destruction
of the cornea (keratomalacia) and leading
tototal blindness

Keratomalacia

• Infection

– loss of mucous membrane lead to increases
susceptibility to bacterial, viral or parasitic
infections

• Hyperkeratinization
of skin

– changes in skin
texture

– skin becomes dry,
scaly & rough

• Growth retardation

Diagnosis for Deficiency

Impaired dark Normal plasma level
adaptation time 20 to 80 µg/100ml

Decreased vitamin
A in plasma

Decreased
RBP in plasma

Tolerable Upper Intake

Age group 1 – 3 years μg/day of preformed
4 – 8 years vitamin A
Infant 9 – 13 years 600
Children 14 – 18 years 600
900
Adolescents 1700
≥ 19 years 2800
Pregnancy & lactation 3000
2800

Toxicity

• Upper Level for Vitamin A

– 3000 μg retinol
– Hypervitaminosis A

• results from long-term supplement use (2 – 4 x
recommended intake)

• bone pain & fragility, vomiting (infant & children), dry,
fissured skin, hair loss (alopecia), anorexia, irritability, fatigue

– Toxicity, fatal dose (12 g)

• Acute toxicity

– short-term megadose (100 x recommended intake)

– symptoms disappear when intake stops
– GI effects, headaches, blurred vision, poor muscle

coordination

• Chronic toxicity

– long-term megadose

– possible permanent damage
– Bone and muscle pain, loss of appetite, skin

disorders, headache, dry skin, hair loss, increased
liver size, vomiting

Health Effects of Vitamin A

Toxicity of Carotenoids

• Hypercarotenemia

– High amounts of carotenoids in the bloodstream
– Excessive consumption of carrots/squash/beta-

carotene supplements
– Skin turns to yellow-orange color

VITAMIN D

Vitamin D

• Steroid vitamin
• A group of fat-soluble pro-hormones
• Which encourages the absorption and

metabolism of calcium and phosphorus

• Not strictly required from diet:

– People who are exposed to normal quantities of
sunlight do not need vitamin D supplements

– Because sunlight promotes sufficient vitamin D
synthesis in the skin

5 forms of vitamin D have been discovered:

D1 D2 D3
D4 D5

2 most important are:

D2 D3
ergocalciferol cholecalciferol

D2 ergocalciferol

• Produced by invertebrates fungus and plants
in response to sunlight (UV irradiation)

D3 cholecalciferol

• Is made in the skin when 7-
dehydrocholesterol reacts with UV light at
270-300 nm wavelengths

• Peak vitamin D3 production occurs between
295-297 nm.

• Vit D2 & D3 require further metabolism to yield
1,25-hydroxyvitamin D (calcitriol), the active
form

• Calcitriol mediates its biological effects by
binding to vitamin D receptor (VDR)

RNI for Malaysia (2017)

Age group 0 – 11 months μg/day
Infant 10
15
1 – 65 years 20
>65 years 15

Pregnancy &
lactation

Food Sources (per 100 g)

Meat/ Poultry/Fish Vitamin D (μg/100g)
Fish, salmon, pink 10.9
7.3
Fish, mackerel, cooked 4.8
Fish, sardines, cooked 2.0
1.2
Egg, whole 0.2
Beef, liver 0.1
Fish, catfish, farmed 0.1
Beef, Meat 0.1
Chicken, Meat
Lamb, meat

Dairy Vitamin D (μg/100g)
Milk, cow fortified, low fat 1.3
Yogurt, fortified, low fat 1.2
1.0
Cheese, cheddar
Vitamin D (μg/100g)
Vegetables 0.7
Mushroom, oyster 0.3
Potatoes, mashed

• Not many foods contain vitamin D
• Fish sources:

– Salmon (447 IU per serving)
– Tuna (154 IU per serving)
– Mackerel (388 IU per serving)
– Fish liver oils (1360 IU per tablespoon)

• Vitamin D is also present in beef liver, cheese
and egg yolks

– Most of these are Vitamin D3

• Some mushrooms provide variable amounts
of vitamin D2 (per 100g):

– Shiitake (raw): Vitamin D2: 0.4 μg (18 IU)
– Portabella (raw): Vitamin D2: 0.3 μg (10 IU)

Functions

Absorption & metabolism of Bones

calcium &
phosphorus

Immune
function

Role - Ca, P & Bone

• Remember

• – Calcitriol mediates its biological effectsby
• binding to VDR - VDR is activated

• VDR activation in the
intestine, bone, kidney, &
parathyroid gland

– leads to the maintenance
Ca & P levels in blood

• with the assistance of
parathyroid hormone
and calcitonin hormone

– and to the maintenance
of bone content

Role in Immune Function

• It is noteworthy that the VDR is
present in activated T cells of the
immune systemin, in antigen-
presenting cells, in macrophages
and monocytes