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Hello. My name is 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 zinc.
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Zinc is involved in many
aspects of cellular metabolism,
and it's required for
the catalytic activity
of hundreds of enzymes.
It's involved in enhancing
immune function,
in wound healing, protein
and DNA synthesis,
cell signalling and division.
Zinc supports healthy growth and
development during
pregnancy, infancy,
childhood, and adolescence,
and it's also involved
in the sense of taste.
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Rich dietary sources
of zinc are meat,
for example, beef, which
contains 4 mg per serving,
an egg contains 0.6 mg of zinc.
Fish is variable:
0.5-1 mg per serving,
except for oysters, which are
an extremely high
source of zinc.
They filter the seawater,
and they acquire a lot of zinc.
So a serving of oysters
would be 30 mg.
Then legumes, grains, and nuts,
all contain high levels of zinc,
from about 0.5 to
1 mg per serving.
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Most zinc is absorbed in
the upper small intestine by
a carrier-mediated process,
and the efficiency of
absorption varies from 20-40%.
It depends on the availability
of zinc for uptake
by the mucosal transporter ZIP4.
Now, the factor that affects
the availability of zinc,
the most important
factor, is phytate.
This is inositol hexaphosphate,
which is a storage
form of phosphorus,
and it's found mainly in the
bran and germ of cereals,
and also in legumes.
Phytate will bind zinc
and prevent absorption.
So one molecule of
phytate can bind
up to six atoms of zinc,
and it makes it unavailable for
uptake by the zinc transporter.
