New research suggests that red wine may prevent cancer despite alcohol use being a major risk factor for head and neck cancer.

Researchers from the University of Colorado Denver found that the chemical resveratrol, found in grapes skins and in red wine, blocks the cancer-causing effect of alcohol.

"Alcohol bombards your genes. Your body has ways to repair this damage, but with enough alcohol eventually some damage  isn't fixed. That's why excessive alcohol use is a factor in head and neck cancer. Now, resveratrol challenges these cells -- the ones with unrepaired DNA damage are killed, so they can't go on to cause cancer. Alcohol damages cells and resveratrol kills damaged cells," Robert Sclafani, investigator at the University of Colorado Cancer Center and professor of biochemistry and molecular genetics, said in a statement.

Some of what is known about the ability of alcohol to cause cancer comes from the study of another disease, Fanconi anemia, a rare genetic disorder that affects about 1 in every 350,000 babies. DNA naturally accumulates tangles called "cross links" and healthy genes can repair and disentangle cross-linked DNA. In Fanconi anemia, people are born without the ability to repair DNA cross links and so DNA damage accumulates. Accordingly, patients with Fanconi anemia are at greatly increased risk of developing cancers including leukemias and also head and neck cancer.

"We learn a lot from genetic disorders because you can put a finger on a gene and say, hey, we know what that does!" Sclafani said.

A genetic accelerator of cancer in Fanconi anemia is the same as the cancer-causing mechanism of alcohol. In both cases, the cause is partially metabolized alcohol. The body metabolizes alcohol by converting it first to acetyl aldehyde and then the body uses aldehyde dehydrogenase (ALDH) to further convert it to acetic acid, which is excreted. The partially processed state of alcohol, acetyl aldehyde, is a carcinogen and produces "cross links" in DNA.

Because Fanconi anemia patients cannot repair the DNA damage produced by acetyl aldehyde, they are at even higher risk for cancer if they also lack ALDH.

"With enough alcohol, the body can get behind and end up with a backlog of acetyl aldehyde," Sclafani said. "Increased exposure to alcohol, loss of the ALDH gene that helps the body process alcohol, and loss of the ability to repair DNA cross links all result in increased cancer risk."

With hard alcohol that's the end of the story: increased risk for head and neck cancer due to increased production of acetyl aldehyde.

The resveratrol in red wine isn't a "magic bullet" that can completely undo the cancer-causing effects of alcohol, but by killing the most dangerous cells it may decrease the probability that alcohol use will cause cancer, Sclafani explained.

The findings are detailed in the journal Advances in Experimental Medicine and Biology.