Binge drinking can cause permanent genetic damage especially to the unborn children of women in the earliest stage of pregnancy, according to a study which shows for the first time how alcohol destroys DNA.
Scientists have identified the precise molecular mechanism leading to the breakdown of the body's natural defences that protect DNA against damage from excessive alcohol in the bloodstream. They believe the results demonstrate that binge drinking causes a build-up of toxins within the body, causing irreversible genetic damage, which may explain the phenomenon known as foetal-alcohol syndrome, when babies of mothers who drink during pregnancy are born with congenital learning problems.
The study was based on genetically-modified mice, but the scientists involved said the findings are applicable to humans and represent a sea-change in the understanding of how alcohol causes long-term physical damage to the body.
"We have long suspected that alcohol causes DNA damage but there has not until now been any direct evidence to support this. This is the first direct evidence that alcohol can cause DNA mutations," said Ketan Patel, who led the research at the Medical Research Council's Laboratory of Molecular Biology in Cambridge.
"This explains why alcohol is toxic to cells and we really needed that explanation. It almost certainly explains why cancer is linked with excessive alcohol consumption, because you cannot get cancer without altering key genes and with alcohol you are essentially drinking a mutagen [mutation-causing substance]," said Dr Patel.
The study, published in the journal Nature, found that a breakdown product of alcohol, called acetaldehyde, is the toxin that damages the DNA molecule within the cells if it is not effectively neutralised by two natural defence mechanisms. The first layer removes acetaldehyde with specialised enzymes while the second repairs the DNA damage that the toxin causes.
"The findings show how critically reliant we are on both these control systems to prevent alcohol from causing irreversible mutations to DNA, both in the foetus and in our own cells," Dr Patel said.
Laboratory mice generated to lack both of these defence mechanisms were highly vulnerable to the effects of alcohol. After being given a dose of alcohol equivalent to a single episode of binge drinking, the foetuses of pregnant mice suffered catastrophic damage.
"The effects of alcohol in the modified pregnant mice resembled foetal alcohol syndrome, where excessive drinking by pregnant women causes permanent damage to the unborn child, leading to birth defects and learning difficulties" Dr Patel said.
"Our work suggests that binge drinking could generate enough acetaldehyde to overwhelm the body's two natural defence mechanisms. This new knowledge transforms our view of precisely how excess alcohol causes damage – ultimately changing our DNA," he said.