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Hello. My name's Susan
Fairweather-Tait.
I'm a professor of
human nutrition at
the Norwich Medical School
at University of East
Anglia in the UK.
I'm going to be
talking about calcium.
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Calcium has a structural
role in the body.
In fact, 99% of
the total body calcium is
found as calcium hydroxyapatite.
It's found in bones and teeth.
The remaining 1% of body calcium
acts as an
intracellular messenger
in cells and tissues
where it plays
a critical role in many
metabolic processes.
These include
vascular contraction
and vasodilation,
muscle contraction,
enzyme activation,
neurotransmission,
membrane transport, glandular
secretion and hormone function.
So, the 1% that's found in
the extra skeletal
compartment of the body.
Although it's small,
has a very vital role
to play in the body.
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So, there are many sources
of calcium in the diet.
Rich food sources include
dairy products and
some vegetables.
Dark green vegetables,
leafy vegetables and broccoli
are a good source of calcium.
Also, legumes such as
pulses and beans, and nuts.
Then, fish with soft
bones that you eat,
such as tinned sardines
they will be a good
source of calcium.
You can also get calcium
in fortified foods.
For example, breakfast cereals
where the calcium is added.
The most important food
group are dairy products.
However, in areas where
there's hard water,
the water itself may
contribute significantly to
the daily intake of calcium
because hard water contains
quite a lot of calcium.
1:39
There are two mechanisms
of absorption of calcium.
First, it's an active
transcellular calcium
transport, which is
saturable, and this involves
a calcium-binding protein
called calbindin.
This takes place in
the small intestine
and it's regulated
predominantly by
vitamin D. The second mode
of absorption is passive.
It's a non-saturable
paracellular uptake
where calcium passes
between the cells of
the mucosa and this happens
with higher intakes of
calcium and as intakes
increase above 500
milligrams a day,
the passive diffusion
accounts for
quite a large proportion of
calcium absorbed throughout
the intestine and there's
no apparent regulation of
this passive uptake root.
There's a dose-response
relationship
