Researchers explain link between alcohol, cancer risk

Almost 30 years after discovery of a link between alcohol consumption and certain forms of cancer, scientists are reporting the first evidence from research on people explaining how the popular beverage may be carcinogenic.

The findings were reported August 22 during the American Chemical Society annual meeting in Philadelphia.

The human body metabolizes the alcohol in beer, wine, and hard liquor into several substances, including acetaldehyde, a substance with a chemical backbone that resembles formaldehyde -- a known human carcinogen, according to lead author Silvia Balbo, PhD, a research associate at the University of Minnesota.

"We now have the first evidence from living human volunteers that acetaldehyde formed after alcohol consumption damages DNA dramatically," Balbo stated in a press release. "Acetaldehyde attaches to DNA in humans in a way that results in the formation of a 'DNA adduct.' It's acetaldehyde that latches onto DNA and interferes with DNA activity in a way linked to an increased risk of cancer."

To test the hypothesis that acetaldehyde causes DNA adducts to form in humans, Balbo and colleagues gave 10 volunteers increasing doses of vodka (comparable to one, two, and three drinks) once a week for three weeks. They found that levels of a key DNA adduct increased up to 100-fold in the subjects' oral cells within hours after each dose, then declined about 24 hours later. Adduct levels in blood cells also rose.

"These findings tell us that alcohol, a lifestyle carcinogen, is metabolized into acetaldehyde in the mouth, and acetaldehyde is forming DNA adducts, which are known major players in carcinogenesis," Balbo said.

People have a highly effective natural repair mechanism for correcting the damage from DNA adducts, so most are unlikely to develop cancer from social drinking, she added. In addition, most people have an enzyme called alcohol dehydrogenase that quickly converts acetaldehyde to acetate, a relatively harmless substance.

However, about 30% of people of Asian descent have a variant of the alcohol dehydrogenase gene and are unable to metabolize alcohol to acetate, resulting in an elevated risk of esophageal cancer from alcohol drinking, the researchers noted. Native Americans and native Alaskans have a deficiency in the production of that same enzyme.

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