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Hello. My name is Susan
Fairweather-Tait.
I'm Professor of
Human Nutrition at
the Norwich Medical School in
the University of East
Anglia in the UK.
I'm going to be talking
to you about iodine.
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Iodine is an obligatory
constituent of
thyroid hormones and the
thyroid hormones are T4,
which is thyroxine and
T3 triiodothyronine.
These are needed
for reproduction,
for metabolic regulation,
for fetal growth and
for brain development.
Their mechanism of action
involves binding to
nuclear receptors.
These are throughout
the body and they alter
the gene expression in
various cells such
as the pituitary,
the liver, the heart,
the kidney and the brain.
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Most iodine is found in
the oceans and iodine ions
and seawater are oxidized
elemental iodine.
This volatilizes in
the atmosphere and
then it's returned to
the soil by rain that
contributes the iodine
cycle if you like.
There's a large variation in
the iodine content
in drinking water.
It's influenced by how far
the country is away from
the sea when the
water is extracted.
The soil content varies
by geographical location.
Iodine deficient soils are
found inland and in
mountainous regions
and areas where there's
frequent flooding because
that leeches out the
iodine from the soil.
The soil pH and the amount of
organic content will affect
the mobilization of iodine
into the food chain.
The iodine content of
foods grown on that soil
will vary depending on pH
and organic composition.
The richest food sources will be
marine products obviously
from the seawater,
fish, shellfish,
mollusks and seaweed.
Also eggs and milk because
the iodine content is
affected by feeding
and hygiene practices.
For example, iodine is added to
animal feeds and
iodophors are used
as a disinfectant in
the dairy industry and that will
affect the amount of
iodine in milk and eggs.
Another source of
iodine is iodized salt.
This is mandatory in many
countries that salt has to be
iodized where they know there's
a public health problem
of iodine deficiency.
There are legislation
to add iodine to salt.
Once iodine has been ingested
foods containing iodine,
