PhDFruit
and
vegetable-‐rich
diets
reduce
blood
pressure
and
risk
of
ischaemic
stroke
and
ischaemic
heart
disease.
Whilst
the
cardioprotective
effects
of
a
fruit
and
vegetable-‐rich
diet
are
unequivocal,
the
exact
mechanisms
of
this
effect
remain
uncertain.
Recent
evidence
has
highlighted
the
possibility
that
dietary
nitrate,
an
inorganic
anion
found
in
large
quantities
in
vegetables
(particularly
green
leafy
vegetables),
might
have
a
role
to
play.
This
beneficial
activity
lies
in
the
processing
in
vivo
of
nitrate
to
nitrite
(a
process
that
has
been
traditionally
viewed
as
detrimental)
and
thence
to
the
pleiotropic
molecule
nitric
oxide.
Ingestion
of
dietary
(inorganic)
nitrate
elevates
circulating
and
tissue
levels
of
nitrite
via
bioconversion
in
the
entero-‐salivary
circulation.
In
addition,
nitrite
is
a
potent
vasodilator
in
humans;
an
effect
thought
to
underlie
the
blood
pressure
lowering
effects
of
dietary
nitrate
ingestion.
In
a
series
of
randomized,
cross-‐over,
placebo
controlled
studies
in
healthy
and
hypertensive
subjects
(n=6-‐20),
I
show
that
single-‐dose
supplementation
with
either
inorganic
nitrate
capsules
(4-‐24
mmol
KNO3)
or
dietary
nitrate
(as
beetroot
juice,
3.3-‐5.5
mmol
nitrate)
elevated
plasma
nitrite
levels
and
reduced
blood
pressure
in
a
dose-‐dependent
manner.
In
a
separate
study,
interruption
of
the
entero-‐salivary
circulation
with
antiseptic
mouthwash
use
for
7
days
reduced
plasma
nitrite
levels
and
elevated
blood
pressure
significantly.
Stratification
of
results
by
sex
revealed
important
differences
in
the
entero-‐salivary
circulation
of
nitrate
to
nitrite
that
had
consequences
on
resting
blood
pressure
and
response
to
nitrate
supplementation.
6
In
conclusion,
these
studies
challenge
the
current
dogma
that
inorganic
nitrate
is
only
detrimental,
and
on
the
contrary
suggests
that
dietary
nitrate
is
important
for
cardiovascular
health.
It
may
be
that
sufficient
supply
of
nitrate
through
the
diet
together
with
functioning,
oral
microflora
is
essential
for
normal
cardiovascular
homeostasis
and
may
be
a
contributing
factor
to
the
lower
blood
pressure
and
vasoprotective
phenotype
of
pre-‐menopausal
women.
Lastly,
the
importance
of
the
oral
microflora
to
maintain
plasma
nitrite
levels
intimates
that
oral
hygiene
treatments
may
disturb
nitrite/nitric
oxide
homeostasis
with
potential
deleterious
effects.British Heart Foundatio
