Diets rich in fat from red meat and dairy products can increase a person's risk of contracting cancer of the pancreas, researchers are warning.

Scientists at the National Cancer Institute in the United States asked more than half a million people to provide precise details of their diet over six years. The team found that those who consumed most animal fat had a higher risk of developing the cancer.

Pancreatic cancer is the 11th most common cancer in Britain. Around 7,600 people are diagnosed with it every year. For most, the prognosis is poor: only 2% to 3% survive for five years or more.

Smoking is rated as the biggest risk factor. While researchers have argued that diet is also involved, past studies have produced inconclusive results. However, Rachael Z. Stolzenberg-Solomon, leader of the institute's pancreatic cancer project, said the new study had revealed a clear association between pancreatic cancer risk and diet, in particular high levels of animal fat. "Reducing fat may reduce the risk of pancreatic cancer," she said.

The researchers collected data on 308,736 men and 216,737 women. Each completed a 124-item food questionnaire in 1995 and 1996.

During an average of six years of follow-up, 1,337 people were diagnosed with pancreatic cancer. Men who consumed the most fat from animal sources had a 53% increased risk of developing pancreatic cancer and women had a 23% increased risk, compared with men and women who ate the least fat, the study found.

In addition, it was discovered that people who ate high amounts of saturated fats had 36% higher rates of pancreatic cancer than did those who ate low amounts.

In a paper published by the Journal of the National Cancer Institute, Stolzenberg-Solomon said the researchers had observed positive associations between pancreatic cancer and intakes of total, saturated, and mono-unsaturated fat, particularly from red meat and dairy food sources.

"We did not observe any consistent association with poly-unsaturated or fat from plant food sources," she said. "Altogether, these results suggest a role for animal fat in pancreatic carcinogenesis."

The importance of the US study was underlined by Josephine Querido, senior science information officer for Cancer Research UK. "This large study adds to the evidence that pancreatic cancer is more common in people who eat too much fat, particularly saturated fat.

"Understanding ways of reducing the risk of pancreatic cancer is very important, because it can be very difficult to treat.

"Apart from stopping smoking, the best way to reduce your risk of cancer is to eat plenty of fruit, vegetables and fibre and to cut down on fatty foods, red and processed meat and limit your intake of alcohol."