Researchers have long known that binge drinking — even only once — during the early stages of pregnancy can cause numerous and serious problems for the fetus, even early postnatal death. Now findings from rodent studies are the first to show that zinc dietary supplements throughout a woman's pregnancy can reduce some alcohol-related birth defects.
The results will be published in the April issue of Alcoholism: Clinical & Experimental Research and are currently available here.
"Alcohol's damage to the fetus depends not only on the amount and duration of alcohol exposure, but also on the timing of the exposure relative to the development stage of the cells and tissues involved," Peter Coyle, associate professor at the Hanson Institute in Adelaide, Australia, and corresponding author for the study, was quoted in a release. He said the this latest work combined with earlier studies had shown that a mother's alcohol use could create a zinc deficiency in fetuses and birth defects related to a protein (metallothionein) binding with zinc in the liver.
On the eighth day of gestation, Coyle and his colleagues injected pregnant mice with either saline or a 25-percent solution of alcohol; all mice were on either a regular or zinc-supplemented diet through the first 18 days of pregnancy. On the 18th day, fetuses from all four groups - saline, saline plus zinc, alcohol, alcohol plus zinc - were assessed for external birth abnormalities. In addition, from birth to day 60, researchers monitored the growth of survivors from all four groups.
"There were three key findings," said Coyle. "One, fetal abnormalities caused by acute alcohol exposure in early pregnancy can be prevented by dietary zinc supplementation. Two, dietary zinc supplementation throughout pregnancy can protect against post-natal death caused by acute alcohol exposure in early pregnancy. Three, dietary zinc supplementation increases the mother's blood zinc to overwhelm the transient drop in zinc caused by alcohol, which we believe prevents the fetal zinc deficiency and subsequent fetal damage."
The rodents' eighth day of gestation is the equivalent of weeks three to eight during a human pregnancy, Coyle noted. "This encompasses a period when the mother is often unaware of her pregnancy and may not have changed her drinking habits," he said. "Moreover, up to 60 percent of pregnancies are unplanned. This latter point is of concern when noting that binge drinking is common in the community and more likely to occur in the first trimester than later."
However, Coyle emphasized, his team is not suggesting that it is safe to drink while taking zinc during pregnancy.
"We have not determined whether zinc protects against all of the possible negative outcomes from alcohol exposure in pregnancy," he said. "Nor would we recommend that makers of alcoholic beverages include zinc in their product so that women can drink while pregnant. Indeed, we take the conservative stand of a ‘no alcohol policy' during pregnancy. What our studies do indicate is that dietary zinc supplementation could be as important as folic acid and applied as a simple prophylactic treatment in the human setting to prevent the effects of a range of insults in pregnancy."
Although zinc tablets can easily be found in herbal shops and many people use the supplements regularly, Coyle cautioned that zinc can also affect the absorption of other trace elements and cause anemia if taken in excess.
"So one must be wary of taking zinc supplements without professional oversight, and this is particularly so in pregnancy."