People who drink two or more sweetened soft drinks a week have a much higher risk of pancreatic cancer, an unusual but deadly cancer, researchers reported on Monday.
People who drank mostly fruit juice instead of sodas did not have the same risk, the study of 60,000 people in Singapore found.
Sugar may be to blame but people who drink sweetened sodas regularly often have other poor health habits, said Mark Pereira of the University of Minnesota, who led the study.
"The high levels of sugar in soft drinks may be increasing the level of insulin in the body, which we think contributes to pancreatic cancer cell growth," Pereira said in a statement.
Insulin, which helps the body metabolize sugar, is made in the pancreas.
Writing in the journal Cancer Epidemiology, Biomarkers & Prevention, Pereira and colleagues said they followed 60,524 men and women in the Singapore Chinese Health Study for 14 years.
Over that time, 140 of the volunteers developed pancreatic cancer. Those who drank two or more soft drinks a week had an 87 percent higher risk of being among those who got pancreatic cancer.
Pereira said he believed the findings would apply elsewhere.
"Singapore is a wealthy country with excellent healthcare. Favorite pastimes are eating and shopping, so the findings should apply to other western countries," he said.
But Susan Mayne of the Yale Cancer Center at Yale University in Connecticut was cautious.
"Although this study found a risk, the finding was based on a relatively small number of cases and it remains unclear whether it is a causal association or not," said Mayne, who serves on the board of the journal, which is published by the American Association for Cancer Research.
"Soft drink consumption in Singapore was associated with several other adverse health behaviors such as smoking and red meat intake, which we can't accurately control for."
Other studies have linked pancreatic cancer to red meat, especially burned or charred meat.
Pancreatic cancer is one of the deadliest forms of cancer, with 230,000 cases globally. In the United States, 37,680 people are diagnosed with pancreatic cancer in a year and 34,290 die of it.
The American Cancer Society says the five-year survival rate for pancreatic cancer patients is about 5 percent.
Some researchers believe high sugar intake may fuel some forms of cancer, although the evidence has been contradictory. Tumor cells use more glucose than other cells.
One 12-ounce (355 ml) can of non-diet soda contains about 130 calories, almost all of them from sugar.