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Hello. My name's Susan
Fairweather-Tait.
I'm a professor of
human nutrition in
the Norwich Medical School at
the University of East
Anglia in the UK.
I'm going to be talking
to you about vitamin A.
Vitamin A is a term
that comprises retinol
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and the family of naturally
occurring molecules
associated with the biological
activity of retinol,
such as retinal, retinoic
acid, and retinyl esters.
It also includes the
provitamin A carotenoids,
that are dietary
precursors of retinal.
Now vitamin A is involved
in vision as retinal,
which plays a central role in
the mechanisms of
phototransduction.
It's also involved in
the maintenance of
growth and integrity of cells in
body tissues through the
action of retinoic acid,
which acts as a regulator
of genomic expression,
and it has an important
role in immune function.
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Vitamin A has a number of
functions in the body.
As I've already explained,
it has an important
role in vision.
It's also involved in cell
growth and differentiation,
and the carotenoids
act as antioxidants.
It also, as I said before,
is important for
the immune system,
and it plays a role in
developmental processes
such as the central
nervous system and bones.
Vitamin A is very important for
embryogenesis and reproduction,
and it also maintains
epithelium integrity.
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Amongst sources in the diet,
preformed vitamin A,
mainly as retinyl esters,
is only found in foods
of animal origin.
It's found to a very high
extent in the liver,
which is offal and
in other meats.
It's found in butter
and margarines
that are fortified
with vitamin A.
It's found in dairy
products and in eggs.
The provitamin A carotenoids
are found in
vegetables and fruits.
Mainly the orange and yellow
colored fruits and vegetables.
It's found in sweet
potatoes, carrots, pumpkins,
is also found in dark
green leafy vegetables,
red peppers,
mangoes, and melons.
