Evolution may have given certain East
Asian populations a genetic defense
against alcoholism, new research
suggests.
Scientists have long known that many
Asian people carry a particular variant
in a gene called ADH1B, which causes
people to become flushed, uncomfortable
or even nauseated after drinking a small
amount of alcohol - making it unlikely
that they'll become alcoholics.
In the new study, however, Yale
University researchers found that only
certain groups in East Asia have a very
high prevalence of the protective gene
variant, while it is less common in
others. The findings suggest that some
environmental factor in the relatively
recent past made the gene variant
advantageous for certain Asian
populations.
The findings are published in the online
journal PLoS One.
The ADH1B gene is one of a set of
related genes that govern certain
enzymes that metabolise alcohol.
A variant of the gene called ADH1B*47His
causes the body to convert ethanol
(alcohol) to the hangover-producing
chemical acetaldehyde more rapidly than
normal.
This, in turn, appears to protect
against alcoholism by making people ill
from even a modest indulgence.
The gene variant is highly prevalent in
East Asia, fairly common in West Asia
and North Africa, and rare elsewhere in
the world.
In the current investigation,
researchers led by Dr Kenneth Kidd, a
professor of genetics at Yale, studied
the prevalence of the protective gene
variant among different East Asian
linguistic groups.
They found that the gene was most common
in two of these groups - those with
Hmong and Altaic languages, which are
scattered widely across Asia.
The fact that the gene variant was
prevalent in these particular groups
suggests that, at some point in the past
few thousand years, something in the
groups' environment caused the gene to
become advantageous - allowing carriers
to survive at higher rates than
non-carriers.
It's not known what that "something"
was. However, it's not likely to be the
anti-alcoholism effect, Kidd said, since
that would not have offered an important
survival advantage.
In fact, he noted, it is only in fairly
recent times that people have been
consuming highly concentrated forms of
alcohol.
One theory, Kidd explained, is that the
gene variant protected certain Asian
groups against a toxin that was present
in their traditional foods, but not
present in the diets of other Asian
groups.
If that protected them from getting
sick, or allowed them to be better
nourished, then that could be a survival
advantage, Kidd said.
Another
theory
is
that
the
gene
variant
offered
protection
against
parasitic
infection,
as
high
levels
of
acetaldehyde
in
the
blood
may
have
proved
fatal
to
certain
parasites.
Historically,
alcoholism
rates
have
been
quite
low
in
certain
Asian
populations,
particularly
in
China.
This
research,
Kidd
said,
aids
in
understanding
why
that
is.
Even
so,
along
with
the
genetics,
there
is
probably
also
a
cultural
component
to
the
low
alcoholism
rates.
Kidd
noted
that
if
it
is
common
for
people
in a
particular
culture
to
get
sick
from
alcohol,
then
alcohol
will
probably
not
turn
up
in
many
social
situations.
Reuters
Health
MiNDFOOD
©
2008