Vitamin A Importance
11:19 AMVitamins
Vitamins
are essential nutrients for the human body growth and development although
these are required in small amount, but have important and specific functions
such as promoting growth, reproduction and the maintenance of health. As they
cannot be synthesized by the body in large enough amount to support the
biological functions performed by our body.
Vitamins
are classified into two groups based on their chemical composition are:
1. Fat soluble vitamins
(Hydrophobic)- Vitamin A,Vitamin D, Vitamin E & Vitamin K found in
oils and fats.
2. Water-soluble vitamins (hydrophilic)-
Vitamin B complex & Vitamin C found in watery part of the food.
Note:- Vitamins do
not give you energy.
Vitamin A
What is
Vitamin A?
Vitamin A is a fat soluble vitamin. There
are different forms of vitamin A including retinol, retinal, retinoic acid, and
retinyl ester which are collectively
referred to
as
retinoids. The most common form of Vitamin A is retinol.
Occur in the precursor form as beta
carotene.
What are the functions of Vitamin A?
Vitamin A having very important
functions for our body are:
1. VisionCell
2. Differentiation of epithelial cells
3. Immunity and growth.
1. VisionCell
2. Differentiation of epithelial cells
3. Immunity and growth.
Function of Vitamin A As Vision
Vitamin A is required for the
production of rhodopsin (A light sensitive material in the rods of retina.)
-
Retinal
turns visual light into nerve signals in retina of eye
-
Retinoic
acid required for structural components of eye
Function of Vitamin A : Cell
Differentiation
Retinoic acid is necessary for
cellular differentiation
Retinoic acid influences production,
structure and functions of epithelial cells that line the outside (skin) and
external passages (mucous forming cells) with in the body.
Function of Vitamin A : Immunity and
growth
Vitamin A is important for embryo
development, gene expression
Deficiency leads to decreased
resistance to infections
Breast cancer – studies have found a
link between
high dietary intake of vitamin A and
a reduced risk of
breast cancer among pre-menopausal
women with a
family history of breast cancer.
Deficiency of vitamin A causes :
- Night Blindness
- Dry skin, dry mucous membrane
- Decreased epithelial cell growth
- Xerophalmia (Have difficuilty in
producing tears)
- Anaemia
- Hypovitaminosis A
Too much intake of vitamin a may
cause :
-
headache
, Vomitting, nausea, Abnormal vision, loss of hair
Vitamin A poisoning : A bizarre case of extreme
vitamin A poisoning was reported by artic explorers who killed and ate a polar
bear. Those who ate the liver become very ill and three of them lost patches of
skin, later scientists discovered that 0.25 lb of the liver contains 2.5 yrs
worth vitamin A for humans.
Fat soluble Vitamins VS water
soluble vitamins
Too much water soluble vitamins that
is too much intake of vitamin B and Vitamin C is alright as it comes out in the
urine but in case of,
Fat soluble vitamins that is
vitamin- A, D, E & K , it cause sickness because it doesn’t dissolve in
your urine readily and get stored in your body
That’s why large intake of vitamin A
can cause harm and toxic to your body.
What are the sources of vitamin A?
The
best dietary sources of vitamin A include eggs, milk, butter, meat, animal
liver and fish liver oils example cod and halibut (the liver stores retinol –
vitamin A).
Milk-
Fortified milk
Carrots etc.
How
do we get vitamin A ?
2
chemicals : retinoid and cortenocoids
-
Retinoid : Body can use right away
- Cortenocoid : Body can change it
into retinoid.hich
Conversion of carotenoids to retinoids
Enzymatic conversion of carotenoids
occus in liver or intestinal cells, forming retinal and retinoic acid
Provitamin A cartenoids
-
Beta
–carotene
-
Alpha-carotene
-
Beta-
carotene
Other cartenoids
Lutein, Lycopene, zeaxanthin.
Absorption of vitamin A ?
In retinoids when retinyl ester
broken down to free in small intestine require bile, digestive enzyme,
itegration into micelles.
Once absorbed m retinyl esters
reformed in intestinal cells. 90% of retinoids can be absorbed
Carotenoids : Absorbed intact ,
absorption rate is much lower in this case.
Intestinal cells can convert
carotenoids to retinoids.
Where does the Vitamin A is
transported and stores ?
Liver stores the 90% of vitamin A in
the body and reserves in adequate for several months
Transported via chylomicrons from Intestinal
cells to the liver and then from liver it transported to the target tissue as
retinol via retinol-binding protein, which is bound to transthyretin.
Where does these retnoids protein
present ?
Target cells contains cellular
retinoids binding proteins
Directs retinoids to functional site
within the cells
Protect retinoids from degradation
Vitamins
Vitamins
are essential nutrients for the human body growth and development although
these are required in small amount, but have important and specific functions
such as promoting growth, reproduction and the maintenance of health. As they
cannot be synthesized by the body in large enough amount to support the
biological functions performed by our body.
Vitamins
are classified into two groups based on their chemical composition are:
1. Fat soluble vitamins
(Hydrophobic)- Vitamin A,Vitamin D, Vitamin E & Vitamin K found in
oils and fats.
2. Water-soluble vitamins (hydrophilic)-
Vitamin B complex & Vitamin C found in watery part of the food.
Note:- Vitamins do
not give you energy.
Vitamin A
What is
Vitamin A?
Vitamin A is a fat soluble vitamin. There
are different forms of vitamin A including retinol, retinal, retinoic acid, and
retinyl ester which are collectively
referred to
as
retinoids. The most common form of Vitamin A is retinol.
Occur in the precursor form as beta
carotene.
What are the functions of Vitamin A?
Vitamin A having very important
functions for our body are:
1. VisionCell
2. Differentiation of epithelial cells
3. Immunity and growth.
1. VisionCell
2. Differentiation of epithelial cells
3. Immunity and growth.
Function of Vitamin A As Vision
Vitamin A is required for the
production of rhodopsin (A light sensitive material in the rods of retina.)
-
Retinal
turns visual light into nerve signals in retina of eye
-
Retinoic
acid required for structural components of eye
Function of Vitamin A : Cell
Differentiation
Retinoic acid is necessary for
cellular differentiation
Retinoic acid influences production,
structure and functions of epithelial cells that line the outside (skin) and
external passages (mucous forming cells) with in the body.
Function of Vitamin A : Immunity and
growth
Vitamin A is important for embryo
development, gene expression
Deficiency leads to decreased
resistance to infections
Breast cancer – studies have found a
link between
high dietary intake of vitamin A and
a reduced risk of
breast cancer among pre-menopausal
women with a
family history of breast cancer.
Deficiency of vitamin A causes :
- Night Blindness
- Dry skin, dry mucous membrane
- Decreased epithelial cell growth
- Xerophalmia (Have difficuilty in
producing tears)
- Anaemia
- Hypovitaminosis A
Too much intake of vitamin a may
cause :
-
headache
, Vomitting, nausea, Abnormal vision, loss of hair
Vitamin A poisoning : A bizarre case of extreme
vitamin A poisoning was reported by artic explorers who killed and ate a polar
bear. Those who ate the liver become very ill and three of them lost patches of
skin, later scientists discovered that 0.25 lb of the liver contains 2.5 yrs
worth vitamin A for humans.
Fat soluble Vitamins VS water
soluble vitamins
Too much water soluble vitamins that
is too much intake of vitamin B and Vitamin C is alright as it comes out in the
urine but in case of,
Fat soluble vitamins that is
vitamin- A, D, E & K , it cause sickness because it doesn’t dissolve in
your urine readily and get stored in your body
That’s why large intake of vitamin A
can cause harm and toxic to your body.
What are the sources of vitamin A?
The
best dietary sources of vitamin A include eggs, milk, butter, meat, animal
liver and fish liver oils example cod and halibut (the liver stores retinol –
vitamin A).
Milk-
Fortified milk
Carrots etc.
How
do we get vitamin A ?
2
chemicals : retinoid and cortenocoids
-
Retinoid : Body can use right away
- Cortenocoid : Body can change it
into retinoid.hich
Conversion of carotenoids to retinoids
Enzymatic conversion of carotenoids
occus in liver or intestinal cells, forming retinal and retinoic acid
Provitamin A cartenoids
-
Beta
–carotene
-
Alpha-carotene
-
Beta-
carotene
Other cartenoids
Lutein, Lycopene, zeaxanthin.
Absorption of vitamin A ?
In retinoids when retinyl ester
broken down to free in small intestine require bile, digestive enzyme,
itegration into micelles.
Once absorbed m retinyl esters
reformed in intestinal cells. 90% of retinoids can be absorbed
Carotenoids : Absorbed intact ,
absorption rate is much lower in this case.
Intestinal cells can convert
carotenoids to retinoids.
Where does the Vitamin A is
transported and stores ?
Liver stores the 90% of vitamin A in
the body and reserves in adequate for several months
Transported via chylomicrons from Intestinal
cells to the liver and then from liver it transported to the target tissue as
retinol via retinol-binding protein, which is bound to transthyretin.
Where does these retnoids protein
present ?
Target cells contains cellular
retinoids binding proteins
Directs retinoids to functional site
within the cells
Protect retinoids from degradation