Drinking soda linked to pancreatic cancer: study

Drinking two or more soft drinks a week may nearly double a person's risk of developing pancreatic cancer, researchers are warning.

Cancer of the pancreas, the disease that killed actor Patrick Swayze last year, is one of the most rapidly fatal tumours in adults; only six per cent of people are alive five years after a diagnosis.

The pancreas makes insulin, and scientists believe high concentrations of insulin can drive the growth of pancreatic cancer cells.

Eating too much sugar increases insulin levels in the body, and one of the leading sources of added sugar in our diets are soft drinks.

The new study, by researchers from the University of Minnesota, was based on more than 60,000 men and women in the Singapore Chinese Health Study who were followed for 14 years. During that time, 140 people developed invasive pancreatic cancer. At the start of the study, as part of a food frequency questionnaire, people were asked to report how often they drank one glass of pop. A glass was considered 237 millilitres, or about the equivalent of one cup.

Those who reported drinking two or more soft drinks per week had an 87 per cent increased risk of pancreatic cancer compared to those who didn't drink soft drinks. The pop drinkers were averaging five drinks per week.

The finding held after researchers took smoking, obesity, diabetes, red meat intake, coffee consumption and a "whole myriad" of other nutritional factors into account, said lead author Noel Mueller, now a research associate at the Georgetown University Medical Center in Washington.

There was no significant association between juice consumption and risk of pancreatic cancer.

The study did not distinguish between regular pop and drinks sweetened with a sugar substitute, as "diet soft drinks did not constitute a significant part of the Singaporean beverage intake at the time the questionnaire was developed," Mueller said.

Other studies have looked at the association between pop and pancreatic cancer, but the results haven't been consistent. One of the strengths of the new study is its size.

However, there were only 140 cases of pancreatic cancer, so the finding was based on a relatively small number of cases.

Mueller also said caution needs to be taken when extrapolating the findings from the Singapore Chinese study to a western population. But other studies in American and European populations have found similar associations.

A study of 88,794 U.S. nurses and 49,364 male health professionals found that women who consumed three or more sugar-sweetened drinks a week had a 57 per cent greater risk of pancreatic cancer than did women who drank no more than one soft drink per month. In that study, there was no association between sweetened soft drinks and pancreatic cancer among men. But a Swedish study involving nearly 78,000 women and men reported in 2006 that high consumption of sugar and high-sugar foods — including soft drinks — was associated with a greater risk of pancreatic cancer in both sexes.

An estimated 3,900 Canadians were diagnosed with pancreatic cancer last year.

The pancreas is a large gland that sits behind the stomach, deep in the upper part of the abdomen. Pancreatic cancer is difficult to detect, because symptoms — such as nausea, vomiting, pain in the upper abdomen or upper back — often only develop in the late stages, and once the disease has begun to spread, "which is often the canary in the mine shaft," Mueller said.

"By the time you do detect this type of cancer, it has often spread to different parts of the body, making it difficult to treat."

Known risk factors include smoking, diabetes and obesity, said Gillian Bromfield, senior manager of cancer control policy at the Canadian Cancer Society.

"There's a lot about pancreatic cancer risk factors that are so unexplained. It's really important to be doing research in this area."

The new study is published this week in the journal Cancer Epidemiology, Biomarkers & Prevention.