Canadian and international cancer experts recommend limiting intake of red meat. (CBC)

People who ate a high-fat diet full of red meat and dairy showed an increased risk of pancreatic cancer, a study suggests.

Pancreatic cancer has the worst relative survival ratios of cancers, with only six per cent of patients living five years after diagnosis, according to the Canadian Cancer Society.

In Friday's online issue of the Journal of the National Cancer Institute, researchers reported men and women who consumed the most saturated fats were 1.36 times more likely to be diagnosed with pancreatic cancer over the six years of followup, compared to people who consumed the least amount of saturated fat.

"[W]e observed positive associations between pancreatic cancer and intakes of total, saturated and monounsaturated fat overall, particularly from red meat and dairy food sources. We did not observe any consistent association with polyunsaturated or fat from plant food sources," Rachael Stolzenberg-Solomon of the Division of Cancer Epidemiology and Genetics at the National Cancer Institute in Bethesda, Md., and her colleagues wrote.

"Altogether, these results suggest a role for animal fat in pancreatic carcinogenesis."

Limit meat intake

In comparison, smoking remains the largest modifiable risk factor for pancreatic cancer, increasing the risk by two- to three-fold, according to an editorial accompanying the study.

In 2007, an international panel of experts recommended that consumers limit their intake of cooked red meat to about 500 grams per week (roughly 700 to 750 grams of uncooked meat.)

The Canadian Cancer Society recommends the same limits on beef and pork consumption for adults, and suggests limiting processed meat like ham to just occasionally, such as a holiday dinner.

The researchers in the latest study collected data on more than a half-million people — 308,736 men and 216,737 women — who participated in the U.S. National Institutes of Health-AARP Diet and Health Study. All participants completed a 124-item food questionnaire in 1995 and 1996.

Over the average of 6.3 years of followup, 1,337 people — 865 men and 472 women — were diagnosed with pancreatic cancer.

The association between red meat and pancreatic cancer was seen in men only, while the association for saturated fat overall and dairy was the same in men and women.

The pancreas secretes enzymes such as lipase to digest fat. The study's authors speculated that fat intake may increase the size and number of cells in the pancreas, making the organ more susceptible to carcinogens.

Obesity, Type 2 diabetes and insulin resistance are also thought to increase pancreatic cancer risk.

Previous studies of diet and pancreatic cancer generated mixed results.

Detailed diet questionnaire praised

But earlier studies were hampered by using less reliable proxy information recalled by next of kin, and difficulty in interpreting blood testing results since the malignancy itself causes changes in patients' nutritional status, Dr. Brian Wolpin of the Dana Farber Cancer Institute in Boston and Dr. Meir Stampfer of the Harvard School of Public Health in Boston said in their editorial.

In contrast, Wolpin and Stampfer praised Stolzenberg-Soloman's study for its large population base, prospective design that limited the need for proxy information, and detailed food questionnaires that included diverse foods, such as low fat options.

"However, the available epidemiological and laboratory evidence are insufficient to confirm the importance of animal fats, per se, or even that meat is the important factor, as opposed to other dietary or lifestyle preferences associated with meat consumption," the pair wrote.

"Nonetheless, sufficient evidence already suggests health benefits from limiting meat and saturated intake, and the current study provides additional support for these recommendations."

They suggested researchers collaborate to increase the number of participants in studies and turn to banked plasma, sperm and tumour tissue samples to advance understanding of the development of pancreatic cancer.

The study was funded by the U.S. National Cancer Institute.