 Zinc may cut alcohol's effect on babies
Source: Dani Cooper ABC Date: 2/3/09
Exposure to alcohol during the early stages of pregnancy is known to increase the risk of fetal abnormalties
The use of dietary zinc supplements during pregnancy could reduce some
alcohol-related birth defects, an animal study shows.
The findings are published today in the online edition of Alcoholism: Clinical & Experimental Research.
Co-author
Associate Professor Peter Coyle, of the Hanson Institute, says drinking
during the first trimester is the greatest period of risk for birth
defects.
He says animal studies have shown fetal abnormalities can occur after just a single "binge-drinking" session.
"This
is particularly relevant as binge drinking is a common pattern of
drinking among women of childbearing age and its prevalence is
increasing," says Coyle in the paper.
He
says earlier studies have shown that fetal zinc deficiency may explain
some of the damage caused by alcohol exposure in early pregnancy.
This
is because zinc is critical to the performance of more than 1000
enzymes and proteins that regulate fetal growth and development, the
paper says.
Coyle
says alcohol causes fetal zinc deficiency because it induces a
zinc-binding protein in the liver known as metallothionein, which
drags the zinc out of the mother's blood into the liver.
Metallothionein
increases zinc levels in the liver, Coyle says, while plasma zinc
concentrations can remain significantly lower than normal for more than
16 hours after exposure to alcohol.
'Extreme caution'
In the latest study, Coyle and his colleagues demonstrate that a zinc-supplemented diet can counteract this process.
Professor
Euan Wallace, clinical director at the Centre for Women's Health
Research at the Monash Institute of Medical Research, says the work by
Coyle's group is very good.
"As
always one must extrapolate animal models (mice) to humans with extreme
caution," says Wallace. "Nonetheless his findings do appear to have
real potential significance for human pregnancy."
For
the study the team made pregnant mice "binge drink" by injecting them
with ethanol on their eighth day of pregnancy, equivalent to weeks
three to eight in a human pregnancy.
The mice were fed from conception with either a regular diet or one that was supplemented with zinc.
Coyle
says in the mice that had been given ethanol, but no zinc, each litter
averaged 26% abnormal fetuses compared with 12% for those mice who
"drank" but also took zinc.
This compared with a control group that had no ethanol or zinc, which averaged 10% abnormalities per litter.
The study also shows zinc supplements prevent postnatal deaths, Coyle says.
Double the deaths
In
a separate cohort of mice the number of postnatal deaths in those mice
that were not treated with zinc, but given ethanol, was double the
number of deaths in any other group.
"If you give zinc early on or at the same time [as alcohol intake is likely to occur] you can get protection," Coyle says.
But
he says the findings would need to be replicated in animals such as
pigs or sheep before any recommendations for humans could be made from
the findings.
Coyle
says they have yet to determine whether zinc protects against all the
possible negative outcomes for alcohol exposure in pregnancy.
"[But]
we believe zinc supplements may be as important as folic acid and
similarly taken as a simple pill in the future," he says.
Folic acid deficiency has been linked with low birth weight and an increased risk of neural disease such as spina bifida.
In Australia, folic acid supplements are recommended for women wanting to become pregnant.
Coyle's
group is now looking at whether stress and infection play a similar
role in causing fetal zinc deficiencies by inducing metallothionein in
the liver.
Tags: diet-and-nutrition, pregnancy-and-childbirth, alcohol
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