06.08.2016
Large prospective study finds higher risk of gallbladder cancer

by Parker Brown
Staff Writer, MedPage Today

People who reported daily consumption of sugar-sweetened drinks had a higher incidence of biliary tract cancer and gallbladder cancer, according to a new study.

Researchers in Sweden studied nearly 71,00 adults and found that those who reported drinking two or more servings of soda or other sugary drinks per day had a greater risk of extrahepatic biliary tract cancer (hazard ratio 1.79, 95% CI 1.02-3.13) and of gallbladder cancer (HR 2.24, 95% CI 1.02-4.89) than did those who drank no soda at all after about 13 years.

But consuming sugary drinks was not linked to significantly higher risk of intrahepatic biliary tract cancer, found the authors, who were led by Susanna Larsson, PhD, and the Karolinska Institutet in Stockholm, Sweden. Larsson and colleagues published their findings in the Journal of the National Cancer Institute on Wednesday.

Larsson and colleagues wrote that the evidence supports the hypothesis that consumption of the drinks are associated with an increased risk of biliary tract cancer, but that more research is needed.

“Further studies of the relation between sweetened beverage consumption, preferably separately for sugar-sweetened and artificially sweetened drinks, and risk of biliary tract cancer and gallbladder cancer specifically are warranted,” they wrote.

Excess body weight and type 2 diabetes have both been linked to biliary tract cancers, wrote the authors, and it’s possible that sugary drinks up the risk of those cancers by causing diabetes and weight gain. But only one study previous to this one has examined the issue, they added, and it included more than 475,00 adults and found no link between gallbladder cancer and consumption of both diet drinks — which contain no sugar and artificial sweeteners — and sugar-sweetened beverages.

Other studies have examined the risk of other types of cancer in the same cohort; consumption has been linked to pancreatic cancer but not to colon cancer or endometrial cancer, the authors noted. “Thus, it does not appear to be a general, nonspecific relation between sweetened beverage consumption and other cancers,” they wrote.

Data for women were drawn from the Swedish Mammography Cohort and for men from the Cohort of Swedish Men. Women completed a questionnaire about their diet, lifestyles, and other risk factors for cancer in 1997. Consumption of sugary drinks was assessed with a food frequency questionnaire that had 96 items. A serving size was 200 milliliters, or about 7 ounces; a can of soda in the U.S. is 12 ounces.

The term “sweetened beverages” on the questionnaire did not include fruit juices, sports drinks, or sweetened coffee, tea, or milk, even though these drinks can have significant amounts of sugar. Compared with those who didn’t consume any soda, those who had more than two servings a day were less likely to have a post-secondary education, were more likely to be overweight, and had higher intakes of total energy, carbohydrates, and sucrose. They also had lower intakes of protein and fat on average.

A possible mechanism is that blood glucose and insulin concentrations affected by consumption could then affect risk of biliary tract cancer. “The biological mechanisms that may link elevated blood glucose concentration to gallbladder cancer risk are unclear, but growth-promoting effects of insulin and insulin-like growth factors are possible mechanisms,” they wrote. Another mechanism could be through gallstone disease.

A significant limitation is the study’s observational design and the reliance on food frequency questionnaires, which can often be inaccurate. In addition, all participants were middle-age adults living in central Sweden, so the results may not be generalizable.

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