Scientists think they know how alcohol damages DNA and increases the risk of cancer.

Researchers in England conducted the study in mice, however, experts say that the mechanisms linking alcohol to DNA damage are the same in mice and men. Indeed, earlier studies have shown strong links between alcohol and certain cancers in humans; in addition, the International Agency for Cancer Research classifies alcohol consumption as “carcinogenic to humans.”

What wasn’t clear, however, was how alcohol did its damage. [7 Ways Alcohol Affects Your Health]

The study, which was published Jan. 3 in the journal Nature, took a precise look at how exposure to alcohol, and the compounds that result when the body breaks down alcohol, cause damage to chromosomes in blood stem cells. These stem cells are crucial for replenishing cells lost throughout the life span, but once they are damaged, they can spread the damage further. (Stem cells can divide and replenish cells for long periods of time.)

In the study, the researchers gave mice doses of alcohol that would be equivalent to an adult human drinking one bottle of whiskey in a short period of time. Some of the mice were genetically engineered to remove two crucial mechanisms that protect against the harmful side effects of alcohol metabolism, leaving the mice vulnerable.

“When the body processes alcohol, it converts it into a highly reactive toxin called acetaldehyde, which damages DNA,” said lead study author Dr. KJ Patel, a tenured principal investigator at MRC Laboratory of Molecular Biology in Cambridge, England.

Patel’s previous work has shown that there are two mechanisms that protect the cells from acetaldehyde. “The first is an enzyme that detoxifies and removes the acetaldehyde,” Patel said. The second mechanism springs into action after the damage is done and is comprised of “DNA repair systems that fix the damage when it occurs,” he said.