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High carbohydrate diet implicated in pancreatic cancer

A diet high in carbohydrates may increase the risk of pancreatic cancer in sedentary and overweight women, some new US research suggests. The study is the first to implicate a modifiable risk factor other than smoking in the development of pancreatic cancer (Journal of the National Cancer Institute 2002;94:1293-300)[Abstract/Free Full Text].

Led by Dr Dominique Michaud of the US National Cancer Institute, and Charles Fuchs of the Brigham and Women's Hospital and the Dana-Farber Cancer Institute in Boston, the researchers set out to determine if foods that raise glucose levels after eating were linked to the development of pancreatic cancer.

They identified 180 cases of pancreatic cancer from among 88802 women who were monitored for 18 years as part of the Nurses Health Study. This is a longitudinal health characteristics survey that started in 1976 with a cohort of 121700 registered nurses aged 30-55. Only ductal adenocarcinomas were studied.

The researchers estimated glycaemic load and glycaemic index from the results reported on a detailed food frequency questionnaire by the study participants. The glycaemic index measures how much a particular food raises glucose compared with a reference food. The glycaemic load is calculated by multiplying glycaemic index by the carbohydrate content of the food.

The average dietary glycaemic load was calculated for each participant, and non-dietary factors were assessed, including smoking, amount and type of exercise, and body mass index. Participants were also asked whether they had a history of diabetes and whether they had had a cholecystectomy.

The associations of glycaemic load and fructose intakes with risk of pancreatic cancer were most apparent among women with raised body mass index ("25). Women who were overweight and sedentary and had a high glycaemic load and high fructose intake were at greater risk of pancreatic cancer, with a relative risk of 2.67 (95% confidence interval 1.02 to 6.99).

Women of normal weight and who were physically active but had high glycaemic loads and high fructose intakes were also at greater risk (53% and 57% increase respectively) than those with low glycaemic loads and low fructose intakes. But these increases were considered insignificant (relative risk 1.53 (0.96 to 2.45) for high glycaemic loads and 1.57 (0.95 to 2.57) for high fructose intake).

The researchers speculate that impaired glucose tolerance may be to blame and that insulin may act as a growth factor for pancreatic cancer.

The study was conducted only in women, but Dr Fuchs said there was no reason to believe the results would not also apply to men. The researchers are now looking to see if there might be other modifiable dietary or behavioural risk factors, apart from smoking, for the development of the disease.

Over 30000 Americans are diagnosed with pancreatic cancer every year. The disease has a poor prognosis, with only 4% of patients surviving five years.

Deborah Josefsen, Nebraska