June 26, 2009 -- New research shows that people who eat a high-fat diet may be more likely to develop pancreatic cancer, especially if their dietary fat comes from animal foods, such as meat and dairy products.
That finding appears in the July 15 edition of the Journal of the National Cancer Institute.
"Our study demonstrated a positive association between dietary intake of total fat, particularly fat from animal sources," researcher Rachael Stolzenberg-Solomon, PhD, RD, tells WebMD. "The strongest associations we observed were from meat and dairy products."
Stolzenberg-Solomon, who is a nutritional epidemiologist at the National Cancer Institute, says previous studies have shown mixed results on whether dietary fat is associated with pancreatic cancer risk.
The new study included more than half a million U.S. adults. When the study started, none of them had pancreatic cancer.
Participants completed surveys about their diets over the previous year, which showed fat intake ranging from 20% to 40% of calories. People who ate a lot of fat were "regular eaters of fat from animals," Stolzenberg-Solomon said.
Participants were followed for six years, on average. During that time, 865 of the men and 472 of the women were diagnosed with pancreatic cancer.
Compared to people with the lowest total fat intake, people with the highest fat intake were 23% more likely to be diagnosed with pancreatic cancer. And people with the highest intake of saturated fats were 36% more likely to be diagnosed with pancreatic cancer.
The study doesn't prove that dietary fat was responsible for that, or that meat or dairy products were particularly to blame. Observational studies like this one show associations, but they don't prove cause and effect.
Still, the findings held regardless of other risk factors for pancreatic cancer, including obesity, smoking, and history of diabetes.
"Our study is in line with the USDA [U.S. Department of Agriculture] guidelines to be prudent and limit fat intake to between 20% and 35% of total calories," says Stolzenberg-Solomon, noting that those USDA guidelines were developed to prevent other diseases.
Stolzenberg-Solomon says other studies are needed to confirm the findings.
Experts Weigh In
The American Cancer Society provided a statement about the study.
"This study is large and well designed, and provides important evidence that a diet high in animal fat may increase risk of one of the leading causes of cancer death. While further confirmatory research about animal fat and pancreatic cancer is still needed, results of this study support the American Cancer Society's recommendations to limit red meat and emphasize plant foods to help reduce risk of a variety of cancer," says Eric Jacobs, PhD, strategic director of pharmacoepidemiology at the American Cancer Society.
Pancreatic cancer researcher Donghui Li, PhD, who is a professor in the department of gastrointestinal medical oncology at the University of Texas M.D. Anderson Cancer Center, also praised the study and said it's still not clear how dietary fat may affect pancreatic cancer risk.
"The study really offers some convincing evidence for the association of dietary fats and pancreatic cancer," says Li, who was part of another team of researchers that published a study this week showing that overweight and obese young adults are more likely than their leaner peers to develop pancreatic cancer later in life.
An editorial published with the study notes that there isn't enough evidence 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."
"Nevertheless, sufficient evidence already suggests health benefits from limiting meat and saturated fat intake, and the current study provides additional support for these recommendations," write the editorialists, who included Brian Wolpin, MD, MPH, of the Dana Farber Cancer Institute in Boston.