Last Updated: 2002-09-03 17:04:42 -0400 (Reuters Health)

By Maggie Fox

WASHINGTON (Reuters) - A diet high in white bread, white rice and potatoes puts women at much higher risk of pancreatic cancer--especially if they are overweight and do not exercise much, researchers reported on Tuesday.

The finding, published in this week's Journal of the National Cancer Institute, adds to research that links a "junk food" diet with a higher risk of certain cancers.

Previously, the only known risk factor for pancreatic cancer, which kills 30,000 people a year in the United States, was smoking.

"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," Dr. Charles Fuchs of the Dana-Farber Cancer Institute, Brigham and Women's Hospital and the Harvard School of Public Health in Boston, who led the study, said in a statement.

"Substituting less starchy vegetables such as broccoli for potatoes and rice and snacking on fruit are some simple steps they can take to reduce this potentially serious health risk."

Fuchs and colleagues used data from the Nurse's Health Study, an ongoing study of 89,000 nurses who carefully record their diet and other habits and whose health is then watched.

They found that eating lots of unrefined starches, such as white bread and potatoes, increased the risk of pancreatic cancer by 57%--but the numbers were just on the border of being statistically significant, meaning the link is not a strong one.

However, Fuchs said some of the nurses were at a much higher risk. "If you took women who were both overweight and sedentary, their risk was 2.5 times higher," he said in a telephone interview.

SEDENTARY LIFESTYLE

There is a good reason to suspect diet may be involved in pancreatic cancer, Fuchs said. "Our presumption is that all these things--being obese, a sedentary lifestyle, a diet high in sugars--all increase insulin levels," he said. Insulin production is one of the pancreas' main functions.

"In the laboratory, insulin promotes the growth of pancreatic cancer cells. We suspect that body states that maintain high levels of insulin increase pancreatic cancer's ability to survive and grow."

Insulin is used by the body to process blood sugar.

Researchers now believe that up to a third of all cancers may be caused by diet and lifestyle. The obvious link is between smoking and lung cancer, but diets high in some fats and perhaps red meat have been associated with colon and breast cancer, for instance.

The American Institute for Cancer Research promotes eating a diet high in vegetables, fruit and whole grains to prevent cancer, as well as getting plenty of exercise.

Pancreatic cancer is an especially deadly cancer, killing all but about 5% of patients within five years.

It is difficult to study because 80% of patients have an advanced stage of the cancer when they are diagnosed. "The principle symptom of pancreatic cancer is profound weight loss--which lowers levels of the key hormones involved," Fuchs said. By then, other genes and chromosomes in the cells have become mutated and the cancer is out of control.

This finding may help people avoid developing the cancer and may eventually lead to better treatments, Fuchs said. And individuals living on typical Western diets should try to eat fewer processed grains and white potatoes anyway, he added.

"There are good reasons to avoid diets that are rich in these foods because they are not only associated in this cohort with pancreatic cancer--they are also associated with and increased risk of cardiovascular disease, heart disease and diabetes," he said

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