Vitamin A is an organic compound that is either obtained through the diet or synthesized in the body. It exists in two major forms: retinoids, which are fat-soluble, and carotenoids, which are water-soluble. Vitamin A deficiency can cause night blindness, dry eyes, susceptibility to infection, and even blindness or death in severe cases. It is commonly caused by diets lacking animal sources of vitamin A and breastmilk from deficient mothers. Too much vitamin A intake can also be toxic, causing nausea, headaches, and birth defects.

1. Vitamin A deficiencyVitamin A deficiency

2.  The term vitamin was historically derived
from "vitamine," a combination word
from vita and amine, meaning amine of
life, because it was suggested in 1912
that the organic micronutrient food
factors which prevented beriberi and
perhaps other similar dietary-deficiency
diseases, might be chemical amines.
Vitamin

3.  vitamin is an organic compound required as
a nutrient in tiny amounts by an organism
 In other words, an organic chemical
compound (or related set of compounds) is
called a vitamin when it cannot be
synthesized in sufficient quantities by an
organism, and must be obtained from the
diet.
Vitamin

4. Vitamins
 Vitamins are classified as either water-
soluble or fat soluble.
 In humans there are 13 vitamins:
4 fat-soluble (A, D, E and K)
9 water-soluble (8 B vitamins and vitamin C
which are dissolve easily in water,
 Because they are not readily stored,
consistent daily intake is important

5. Function
Vitamins have diverse biochemical functions.
 Some have hormone-like functions as regulators of
mineral metabolism (e.g. vitamin D)
 Regulators of cell and tissue growth and
differentiation (e.g. some forms of vitamin A)
 Others function as antioxidants e.g. vitamin E and
sometimes vitamin C
 The largest number of vitamins (e.g. B complex
vitamins) function as precursors for enzyme cofactors,
that help enzymes in their work as catalysts in
metabolism.

6. Vitamin A deficiency
 Vitamin A deficiency is a lack of vitamin A in humans.
It is common in developing countries but rarely seen in
developed countries
 Night blindness is one of the first signs of vitamin A
deficiency.
 Night blindness is the difficulty for the eyes to adjust to
dim light. Affected individuals are unable to distinguish
images in low levels of illumination. People with night
blindness have poor vision in the darkness, but see
normally when adequate light is present.

7. Vitamin A deficiency
 Xerophthalmia
Which is a medical condition in which the eye
fails to produce tears that leads to conjunctival
dryness and damage, complete blindness can
also occur since Vitamin A has a major role in
phototransduction.
 Phototransduction
Is a process by which light is converted into
electrical signals in the cells of the retina of the
eye

8. Vitamin A deficiency
 Vitamin A deficiency also diminishes the ability to fight
infections. In countries where children are not
immunized, infectious disease like measles have
higher fatality rates.
 Even mild, subclinical deficiency can also be a
problem, as it may
 Increase children's risk of developing respiratory and
diarrheal infections
 Decrease growth rate
 Slow bone development
 Decrease probability of survival from serious illness.

9. Causes of vitamin A deficiency
 The major cause is diets which include few
animal sources of pre-formed vitamin A.
 Breast milk of a lactating mother with
vitamin A deficiency contains little vitamin
A, which provides a breast-fed child with
too little vitamin A.

10. Causes of vitamin A deficiency
 In addition to dietary problems, there are other
causes of vitamin A deficiency
 Iron deficiency can affect vitamin A uptake.
 Excess alcohol consumption can deplete vitamin A
 A stressed liver may be more susceptible to vitamin
A toxicity.

11. Hypervitaminosis A
 Hypervitaminosis A refers to the effects of excessive
vitamin A) specifically retinoid) intake
 Hypervitaminosis A occurs when the maximum limit for
liver stores of retinoids is exceeded.
 The excess vitamin A enters the circulation causing
systemic toxicity.
 Betacarotene (is an organic compound which is a
strongly-coloured red-orange pigment abundant in plants
and fruits. β-Carotene is also the substance in carrots that
colours them orange) a precursor of vitamin A, is
selectively converted into retinoids, so it does not cause
toxicity.

12. Retinoids
 The retinoids are a class of chemical compounds that
are related chemically to vitamin A.
 Retinoids are used in medicine, primarily due to the way
they regulate epithelial cell growth.
 Retinoids have many important and different functions
throughout the body including
 Roles in vision
 Regulation of cell proliferation and differentiation
 Growth of bone tissue
 Immune function
 Activation of tumor suppressor genes.

13. Hypervitaminosis A
Signs of acute toxicity include
 Nausea
 Vomiting
 Headache
 Dizziness
 Blurred vision
 Loss of muscular coordination

14. Other effects
 Birth defects
 Liver problems
 Skin discoloration
 Hair loss
 Excessive skin dryness
 Angular cheilitis is an inflammatory lesion at the labial
corner of the mouth, and often occurs bilaterally. The
condition manifests as deep cracks or splits. In severe
cases, the splits can bleed when the mouth is opened and
shallow ulcers or a crust may form.
Hypervitaminosis A