More bad news for soda-drinkers: A University of Minnesota study suggests that drinking two or more soft drinks a week nearly doubles the risk of developing pancreatic cancer.

Mark Pereira, an associate professor at the School of Public Health, and his research team studied the dietary habits of more than 60,000 adults in Singapore for 14 years. They found that those who drank high amounts of sugar-sweetened carbonated beverages were 87 percent more likely to develop pancreatic cancer than those who did not, according to a study released Monday.

Overall, the risk was still relatively small: Only 140 of the study subjects developed pancreatic cancer.

But the disease is so deadly -- with just a 5 percent survival rate after five years -- that scientists are eager to find any way to reduce that risk, said Pereira, who specializes in the dietary causes of illness.

"It's a silent disease," he said, "You don't know you have it until you are sick, and then you are dying from it."

How could a few soft drinks a week lead to cancer? Pereira said it could reflect the drinks' effect on insulin, the hormone produced in the pancreas.

"When you drink soft drinks, you get a burst of blood sugar," he said. "What the pancreas does in response almost immediately is secrete insulin to bring the blood sugar down."

The theory, he said, is that high levels of insulin in the pancreas could promote the growth of cancer cells.

Pereira didn't study diet soda, but he said he believes it would not have the same effect.

Previous studies have suggested a link between sugar-laden drinks and pancreatic cancer, Pereira said. He said portion size may play a role, noting that soft drinks "are [often] served up in ridiculously large portion sizes."

Interestingly, the study did not find the same effect with fruit juices. "Fruit juice has some nutrients, a lower sugar concentration, and is generally served in smaller portions," Pereira said.

Pereira's findings did not convince all observers.

"The low number of cases makes any even tentative statements about cause-effect worthless," said Dr. Gil Ross, medical director of the American Council on Science and Health, a New York group partly funded by the food and soft-drink industry.

"Prior studies in general have found no significant effect of soda or sugary drinks" on pancreatic cancer, he noted.

Pereira acknowledges that more study is needed. "There are limitations to observational research," he said.

The study is being published in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.

Megan Hanson is a University of Minnesota student reporter on assignment for the Star Tribune.