Nearly 30,000 men and women in the United States are diagnosed with pancreatic cancer each year, and an equal number die from it. Five-year survival rate is only about four percent.

"Our findings add to the growing body of evidence that suggests that insulin may have a role in the development of pancreatic cancer," explains senior author Charles Fuchs, M.D. "Further research is needed, however, to track the connection in more detail."

"Historically, cigarette smoking had been the only proven risk factor for developing pancreatic cancer," says the study's lead author, Dominique Michaud, Sc.D. "We're working to determine whether there are dietary or behavioral risk factors -- ones that can be modified. At the same time, we hope to learn more about the basic biology of the disease."

The researchers reasoned that if insulin fuels growth of pancreatic cancer cells, then foods that stimulate production of large amounts of insulin should be associated with a higher incidence rate. Data came from the Nurses' Health Study, a project that tracks health information on female nurses across the United States. The researchers reviewed dietary records of nearly 89,000 nurses to measure intake of sucrose, fructose, and carbohydrates.

The researchers calculated the amount of glucose-stimulating food (the glycemic load) of each study participant. The ability of carbohydrate-containing foods to boost glucose -- and thereby insulin -- levels is known as the glycemic index. Starchy foods such as potatoes, white rice, and white or rye bread -- all staples of the American diet -- have high glycemic indexes.

The researchers found that women who were significantly overweight and physically inactive (and whose levels of glucose and insulin were therefore already above normal) were more than two-and-a-half times more likely to develop pancreatic cancer if they had a high glycemic load than if they had a low load. Interestingly, a high glycemic load did not increase pancreatic cancer risk among women who were lean and physically fit.

An analysis of pancreatic cancer rates in all women in the study showed that women who had high glycemic loads were 53 percent more likely to develop pancreatic cancer than those with low loads. Women who consumed large amounts of fructose had a 57 percent greater risk of pancreatic cancer. The researchers note that neither of these trends reached statistical significance due to the limited number of cancer cases in each category.

Although the study involved only women, the researchers point out that is no reason to think that the findings do not apply equally to men.

"The take-home message for women who are overweight and sedentary is that a diet high in starchy foods may increase their risk of pancreatic cancer," says Fuchs. "Substituting less starchy vegetables such as broccoli for potatoes and rice and snacking on fruit are some simple steps that they can take to reduce this potentially serious health risk."