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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 about folate,
one of the B vitamins,
sometimes referred
to as vitamin B9.
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Folate functions as a
cofactor or co-substrate in
numerous one-carbon
transfer reactions that
are important for the
synthesis of RNA and DNA,
amino acid interconversions, and
the process of methylation.
In summary, folate
is required for
the production of
RNA and DNA for
red blood cell formation and for
the healthy function of the
brain and nervous system.
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Foods which are rich
sources of folate include
dark green leafy
vegetables, legumes,
oranges, peanuts and almonds,
liver and kidney, fortified
breakfast cereals
to which it's added,
and baker's yeast.
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Folate is a generic term
that covers all forms of folate.
In food, naturally
occurring folate is
a mixture of reduced mono and
polyglutamates,
whereas folic acid is
the monoglutamate,
and it's only found
in fortified foods
and food supplements.
The bioavailability of folic
acid is quite high at 85%
whereas, food folates
are around 50%.
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The food polyglutamates
are converted to
monoglutamates by glutamate
carboxypeptidase,
and they're absorbed in the
proximal small intestine by
the protein-coupled
folate transporter
or the reduced folate carrier.
High doses of folate are also
absorbed by passive
diffusion in the ileum.
In the enterocyte,
the reduced folates
are converted into
tetrahydrofolate
and transported to
the portal vein by
multidrug resistance-associated
protein three.
Once it's been absorbed,
