Alcohol and cancer have a complicated relationship. While medical organizations have concluded that alcohol consumption is a risk factor for some forms of cancer, it isn't clear exactly why. A new study published in the international science journal Nature last month offers more clues.
Researchers from the University of Cambridge injected diluted ethanol (the alcohol in beverages) into lab mice, and used DNA sequencing and chromosome analysis to assess the damage done to the animals' blood stem cells. They found that acetaldehyde, a harmful chemical produced when the body processes alcohol, can split and damage DNA within the stem cells, causing mutations that may lead to a higher cancer risk.
"Some cancers develop due to DNA damage in stem cells," said Dr. Ketan Patel, lead author of the study and scientist at the Medical Research Council Laboratory of Molecular Biology. "While some damage occurs by chance, our findings suggest that drinking alcohol can increase the risk of this damage."
The human body has a two-tier defense mechanism to protect against acetaldehyde's effects. The first tier is an enzyme called aldehyde dehydrogenase 2 (ALDH2), which essentially clears the toxic acetaldehyde out of the body.
Some humans, particularly those of Southeast Asian descent, struggle to produce ALDH2. To test just how effective ALDH2 is, the researchers genetically modified a group of mice so their bodies could not produce ALDH2, and then gave them the same dose of alcohol as the non-modified mice. "We can show that one dose of alcohol is enough to induce four times more DNA damage than in normal mice," Patel told Wine Spectator.
But even those who lack the critical enzyme still have the second tier of defense: DNA repair functions, which deal with DNA that's already been damaged. This is not a fail-safe plan, however. "The majority of cells that carry the snapped DNA are killed, but some of the cells put it back together, [and some] put it together the wrong way," Patel explained. This can result in a potentially cancer-causing mutation.
In terms of what types of cancer these mutations may cause, we know that alcohol consumption has been associated with a higher risk of certain cancers, most notably breast cancer. But blood cancer isn't one of these. So why did the researchers choose to test on blood stem cells?
"We used blood in this instance because it's an easy population to experiment with and manipulate and study, whereas stem cells in other organs—where cancer is known to occur if you expose yourself to alcohol—are more difficult to study," Patel explained. "Because alcohol can damage the genome of a blood stem cell, it's likely to damage the stem cells that contribute to [other parts of the body] as well."
It's important to note that those with both defense mechanisms intact have a lot less to worry about than those who do not. Fortunately, it's fairly easy to detect an ALDH2 deficiency. First, and most noticeably, those lacking ALDH2 get extremely red skin when they drink. Another way to find out is with an ethanol patch test, in which skin is put into contact with alcohol to test for reddening. The most conclusive method is a DNA test.
A self-described wine connoisseur, Patel says he is interested in seeing if low doses of alcohol could actually help the body clear out acetaldehyde. But for now, he is just concerned with the facts: "As a scientist, my primary job is to provide evidence; [as wine drinkers], it's up to us what choices we make with it."
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