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0:00
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 about cobalt.
0:14
Cobalt is an essential
component of vitamin B12
and it plays an
important role in
the formation of the
myelin sheath in
nerve cells and the formation
of amino acids and
some proteins.
So, cobalt itself
is not essential,
but vitamin B12 is.
Dorothy Hodgkin in 1955 and
her colleagues published
the final structure
of vitamin B12,
which they obtained by
X-ray crystallography.
She was awarded
the Nobel Prize in
chemistry in 1964 for this work.
You can see the structure of
vitamin B12 with cobalt at
the center of it on the
right-hand side of the slide.
0:51
If we look at cobalt intakes,
the average intake ranges
from 5-8 micrograms per day,
which is a very small amount and
it's often called a
trace element and
vitamin B12, although
it contains cobalt,
it's only about 4%
of the molecule.
So, it's not considered to be
a dietary supply of cobalt,
but cobalt is widely
distributed in the diet.
It's mainly present in
the form of arsenide,
oxide, and sulphide,
but the content of plants
and animal foods will
depend on the concentration
of the soil and
water from where the
food originates.
So, it's very much affected
by the environment.
The foods we know have
a high content of
cobalt include: yeast
products and yeast,
coffee, nuts, seeds and grains,
cereals, and chocolate
and condiments.
1:38
So, cobalt can enter into
the body by several
different routes.
First is the oral intake,
which is what I'm going to
concentrate on today
because that's nutrition,
but you can get cobalt
through the air,
through your lungs, and
also through your skin.
Then, cobalt-chromium implants
such as those used for hip
and knee replacements,
these will also introduce
some cobalt into the body.
The absorption of the diet
averages something from 57-97%.
It's quite variable and
these figures are found
from balance studies.
So, they're not
terribly accurate,
but we can see it's quite
a big range in absorption.
The duodenum and
the upper intestine
are the primary sites for
cobalt ion absorption.
Now, the absorption is affected
by a number of things.
The chemical form of cobalt
will affect how
well it's absorbed;
the dose; the formation of
complexes with organic ions.
This will happen in
the lumen of the gut.
Also, the age and
the nutritional status of
the individual will
have a great effect.
For example, if somebody
is iron deficient
because iron is transported
on the same
transporter as cobalt,
which is divalent
metal transporter
(DMT-1 in the gut).
If you're iron deficient,
you will produce
a greater amount
of DMT-1 because you're
trying to acquire iron.
You require it. You will
at the same time have
more protein transport ready
to take cobalt into the body.
So, if you're iron deficient,
you will absorb cobalt to
a much greater extent than if
you have a normal iron status.
