Beer, bugs, DNA linked to stomach cancer
Genetic variant, low-grade infection and guzzling can add up to trouble
By Nathan Seppa
ORLANDO, Fla. — Swilling at least three beers a day over several years can increase a person’s risk of stomach cancer if combined with two other unseen risk factors, researchers have found. But oddly, wine and liquor didn’t show the same danger level for this malignancy, the team reported April 4 at a meeting of the American Association for Cancer Research.
The triple threat includes carrying two copies of rs1230025, a gene variant located amid a cluster of genes associated with degrading alcohol in the body. The third risk factor is an infection with Helicobacter pylori, a well-known bacterium that causes stomach cancer and ulcers. H. pylori infection is uncommon in the United States, but roughly half the world’s population carries the microbe.
Eric Duell, an epidemiologist at the Catalan Institute of Oncology in Barcelona, and his colleagues analyzed data on health status and alcohol intake among thousands of adults participating in a European study between 1992 and 1998. The researchers found a broad link between stomach cancer and drinking three or more beers daily, but no clear association for similar amounts of wine or liquor.
The researchers then focused on 364 people who had been diagnosed with stomach cancer and 1,272 others without cancer to test the combined effects of beer intake and having the variant gene. People who drank three beers or more daily showed a slight increase in stomach cancer risk if they carried one copy of the gene variant, compared with similar drinkers without the variant. Also, very modest drinkers who carried two copies of the variant had a slightly increased risk over similar drinkers without it.
But those with high beer intake who also carried two copies of the variant gene had a 3- to 22-fold increase in stomach cancer risk compared with heavy drinkers who didn’t carry a variant copy. Nearly all people with stomach cancer had H. pylori infections, which the researchers took into account in calculating risk differences.
The three risk factors all appear necessary for the heightened risk, but the direct cancer-causing event is probably inflammation, Duell says. Many lines of research have linked inflammation with increased cancer risk, and the triple whammy cited in the new study would boost chronic gastritis, or stomach inflammation, he says.
“It all makes physiological sense,” says George Kim, a gastrointestinal oncologist at the Mayo Clinic Florida in Jacksonville who wasn’t part of this study. “If you cut off the enzymes that break down alcohol, then that causes problems over time. Throw in H. pylori and that’s another hit,” he says.
About 20 percent of people carry at least one copy of the variant form of the gene, Duell says.
Meanwhile, it remains unclear which compounds found in beer might account for the different risk found between it and other alcoholic beverages, he says.
The United States has low rates of stomach cancer because of its dearth of H. pylori, Kim says. But the disease remains the second-leading cause of cancer death worldwide after lung cancer, suggesting genetic screening would have value, he says.
