RESEARCHERS believe they have discovered two genes which allow people to hold their drink.
Carriers of one or both genes can process alcohol through the body quickly.
One effect is that it halves the chance of developing mouth, throat and oesophageal cancer.
However, only a minority of people in the UK have the genes. They belong to
the ADH range, which everyone has two of – one inherited from each parent – but just 15% to 20% have ADH7, while 5% have ADH8, which both combat the detrimental health effects of drinking.
The study of 9,000 people in the UK, including residents of Edinburgh, has been published in the journal Nature Genetics.
Professor Martin Wiseman, medical and scientific adviser to the World Cancer Research Fund, which helped to finance the study, said: "We don't know how the protection occurs, but we do now know that these genes have that effect and that could be hugely useful in giving us a much broader understanding of cancer processes in general."
Alcohol is a major cause of cancer and is estimated to be responsible for about 5% of the 285,000 new cases diagnosed in the UK every year.
Health expects have welcomed the findings but warned against them being seen as a green light to drink heavily.
Professor Martin Wiseman said: "This shouldn't have any direct effect on people's drinking behaviour.
"Those people with one or both of these rare gene variants are lucky in that they are lesser risk of developing these cancers. Having up to half the risk is significant.
"But they still face some risk. So the advice to them wouldn't be, 'Go away and drink.'"
People are not able to find out if they carry the genes, as family doctors would not know, and there is no reliable test that can be easily accessed.
Dr Paul Brennan, the researcher who led the study at the International Agency for Research on Cancer in France, said:
"Those 20% to 25% of people who have one or both are gene variants – if they drink alcohol, their risk of getting these head and neck cancers is reduced by about half."
