Researchers have found the first conclusive evidence in humans that many people's favorite beverage is a carcinogen. The discovery comes 30 years after scientists had found a link between alcohol consumption and certain types of cancer.

The University of Minnesota's Silvia Bilbao, a research associate in noted cancer expert Steven Hecht's laboratory, presented her findings at the 244th National Meeting and Exposition of the American Chemical Society.

The human body breaks down the alcohol in wine, beer and hard liquor. After breaking it down, one of the chemicals formed is acetaldehyde, a compound with a backbone that resembles formaldehyde. Formaldehyde has long been identified as a carcinogen in humans. Scientists also have known for a long time that acetaldehyde can trigger damage to DNA, cause chromosomal mutations in cell cultures and is a carcinogen in animals.

But the research from Bilbao and her team was notable because it was the first one to have studied the effect that acetaldehyde has on humans. They found that drinking alcohol changed DNA drastically. Acetaldehyde attaches to DNA in humans and increases with its activity so as to put humans at increased risk of cancer. That attachment is called a 'DNA adduct.'

The team gave study volunteers increasing amounts of vodka once a week over the course of three weeks. The doses were equivalent to one, two, and then three shots of vodka. They found that levels of a key DNA adduct rose by 100 times in the participants' oral cells. Adduct levels in blood cells also rose.

In most people, the body has an effective way of repairing the damage caused by DNA adducts, so they are unlikely to develop cancer as a result of social drinking. Most people also can easily convert acetaldehyde to acetate, a harmless substance.

But some people lack that ability. For example, 30 percent of people of Asian descent, about 1.6 billion people, lack the ability to properly metabolize alcohol to acetate, putting them at an elevated risk for the development of esophageal cancer. Native Americans and native Alaskans also often are deficient in that capability.

The study was hampered by its short duration of time, but subsequent studies on the matter will surely be longer.