2. Thirteen vitamins are necessary for health
Vitamins A, D, E, and K are fat-soluble, and
all others are water-soluble
3. The distinction between fat- and water-
soluble vitamins is important.
Fat-soluble vitamins are more readily
stored in the body, but they may be poorly
absorbed in fat malabsorption disorders
4. A deficiency of vitamins may be
primary (dietary in origin) or
secondary because of disturbances in
intestinal absorption, transport in the blood,
tissue storage, or metabolic conversion
5. Vitamin A
Vitamin A is the name given to a group of
related compounds
retinol (vitamin A alcohol),
retinal (vitamin A aldehyde),
retinoic acid (vitamin A acid)
The generic term retinoids encompasses
vitamin A in its various forms and both
natural and synthetic chemicals that are
structurally related to vitamin A
6.
7. Functions of vitamin A
Maintenance of normal vision
Cell growth and differentiation
Metabolic effects of retinoids
Host resistance to infections
8. Vitamin A Deficiency
Earliest manifestations of vitamin A
deficiency is impaired vision, particularly in
reduced light (night blindness).
Persistent deficiency gives rise to a series
of changes involving epithelial metaplasia
and keratinization.
9. The most devastating changes occur in the
eyes and are referred to as xerophthalmia
(dry eye).
First, xerosis conjunctivae
Buildup of keratin debris in small opaque
plaques (Bitot spots) and, eventually,
Erosion of the roughened corneal surface with
softening and destruction of the cornea
(keratomalacia) and total blindness.
10. Epithelium lining the upper respiratory
passage and urinary tract is replaced by
keratinizing squamous cells (squamous
metaplasia)
Another very serious consequence is
immune deficiency
11.
12. Vitamin A Toxicity
Acute
Chronic
Well-established teratogenic effects of
retinoids – contraindicated in pregnancy
13. Vitamin D
Major function of the fat-soluble vitamin D
is the maintenance of adequate plasma
levels of calcium and phosphorus
Metabolic functions,
Bone mineralization, and
Neuromuscular transmission
14. Rickets (in children whose epiphyses have
not already closed)
Osteomalacia (in adults), and
Hypocalcemic tetany [Extracellular
concentration of ionized calcium, which is
required for normal neural excitation and
the relaxation of muscles]
15.
16.
17. Normal reference range for circulating 25-
(OH)-D is 20 to 100 ng/mL;
concentrations of less than 20 ng/mL
constitute vitamin D deficiency
Causes
Diet deficiency
Limited exposure to sunlight
Renal disorder
19. Rickets
Most common during the first year of life.
The gross skeletal changes depend on
the severity and duration of the process
the stresses to which individual bones are
subjected.
20. During the nonambulatory stage of infancy,
the head and chest sustain the greatest
stresses.
Craniotabes
Frontal bossing and a squared appearance
to the head
Rachitic rosary
Pigeon breast deformity
21.
22. Ambulating child deformities are
likely to affect the spine, pelvis,
and tibia
lumbar lordosis and bowing of the
legs
23. In adults, the lack of vitamin D deranges
the normal bone remodeling that occurs
throughout life.
Production the excess of persistent
osteoid that is characteristic of
osteomalacia.
Bone is weak and vulnerable to gross
fractures or microfractures, which are most
likely to affect vertebral bodies and femoral
necks.
24. Non-Skeletal Effects of Vitamin
D
Effective against infection by
Mycobacterium tuberculosis (stimulates
the synthesis of cathelicidin, an
antimicrobial peptide from the defensin
family)
Innate and adaptive immunity
Gene expression (>200 genes)
Ca colon, prostrate, breast
25. Vitamin C (Ascorbic Acid)
Scurvy, characterized principally by
bone disease in growing children and
by hemorrhages and healing defects in both
children and adults
Vitamin C is present in milk and some
animal products (liver, fish) and is
abundant in a variety of fruits and
vegetables
26. Function
Best-established function of vitamin C is
the activation of prolyl and lysyl
hydroxylases from inactive precursors,
providing for hydroxylation of procollagen
Collagen, which normally has the highest
content, of hydroxyproline, particularly in
blood vessels, accounts for the
predisposition to hemorrhages in scurvy
27. Antioxidant properties
scavenge free radicals directly and
Act indirectly by regenerating the antioxidant
form of vitamin E