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By Susan
Hickman
 When
Brian Foster
gulped down
an
eight-ounce
glass of
cranberry
juice one
morning, he
had no idea
what was in
store. A few
hours later,
as he walked
down the
halls of the
University
of Ottawa’s
Faculty of
Medicine
where he
teaches, his
blood
pressure
dropped
suddenly and
he began to
stumble.
The episode
soon passed,
but Foster
realized his
“overdose”
of cranberry
juice had
interfered
with his
medication,
metoprolol,
a
beta-blocker
used to
treat high
blood
pressure.
“The
reaction was
my own
fault,” says
Foster, who
studies
common foods
such as
cranberry
juice and
other
natural
health
products
from
Canadian
sources.
Foster’s a
senior
science
advisor and
a member of
the
digestive
diseases
research
group in
Health
Canada’s
science
laboratory.
For nearly a
decade, he’s
been
examining
the effects
some natural
and herbal
products may
have on the
way patients
metabolize
prescription
drugs.
About nine
years ago,
he learned
garlic could
interfere
with the
AIDS drug
Ritonavir. A
doctor in
Manitoba had
discovered a
link between
garlic and
two of his
AIDS
patients
when they
developed
severe
reactions.
One had
eaten a
whole garlic
bulb a day.
The other
was taking
three times
the
recommended
dose of
garlic
tablets.
Foster began
to look at
other
alternative
medicines
and natural
health
products
such as
evening
primrose
oil, Earl
Grey tea,
Echinacea,
St. John’s
wort, and
even red
wine.
Although red
wine is
often
promoted as
“heart
smart,” in
fact, Foster
and his team
have found
that eight
red wines
have a very
high
potential to
interfere
with drug
metabolism.
“I’ve been
keeping away
from red
wine,” says
Foster, who
has a heart
condition.
“There are
many heart
patients out
there who
could suffer
a negative
effect from
red wine.”
Add a plate
of
exotically
spiced curry
– perhaps
with ginger,
cumin,
turmeric or
even
cinnamon –
and the
combination
could be
even more
threatening.
“All
chemicals
carry a risk
for most
people,”
warns
Foster. “The
risk is very
low, but
there are
some people
who are at
higher risk.
And those
who are on
drugs for
AIDS or
cancer,
immuno-suppressives
for
transplants,
or some
antibiotics
for cystic
fibrosis
face the
risk of
something
happening.”
Health
Canada, says
Foster, is
trying to
get this
message out
in a
“user-friendly
way,” and
making sure
drugs carry
the
appropriate
warnings.
“Don’t stay
away from
foods you
like,”
Foster
advises,
“but be
cautious. We
suggest
people
follow a
balanced
diet in
moderation.
We find that
when people
have eaten
large
amounts of
one thing,
together
with their
drugs,
that’s when
these things
seem to
happen.”
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