For years, the common assumption has been simple: eating less fat may help lower cancer risk. However, new research suggests the picture is much more complicated.

Scientists have discovered that when it comes to pancreatic cancer, the specific type of fat in the diet may be more important than the total amount consumed.

The findings, published in Cancer Discovery, a journal of the American Association for Cancer Research, indicate that different fats can have dramatically different effects on cancer development.

According to Christian Felipe Ruiz, PhD, an associate research scientist in Yale School of Medicine’s Department of Genetics and lead author of the study, ‘It’s really the type of fat that you’re consuming, not just total fat content.’ Depending on the type of fat consumed, it can go completely different ways.

The study found that some fats promote cancer, as expected, while other fats are really good at suppressing cancer.

One Fatty Acid May Encourage Tumor Growth

One of the study’s most unexpected findings involved oleic acid, the primary fatty acid found in olive oil.

Researchers found evidence that oleic acid may encourage tumor growth in pancreatic cancer, a result that surprised the team because of the fatty acid’s long-standing reputation as a heart-healthy dietary fat.

It’s traditionally been considered a healthy type of fat for cardiovascular health, Ruiz says.

Cancer-Associated Fatty Acid

The cancer examined in the study was pancreatic ductal adenocarcinoma (PDAC), the most common form of pancreatic cancer and one of the deadliest cancers overall.

Only about 13% of people diagnosed with PDAC survive for five years.

More than 65,000 people are expected to be diagnosed with PDAC in the U.S. this year, with over 50,000 deaths.

At the moment, effective treatment options are limited, especially for advanced disease. Therefore, prevention strategies are sorely needed to move the needle on PDAC mortality.

Comparing Different Types of Dietary Fat

To isolate the effects of specific fats, the researchers created 12 different high-fat diets.

Each diet contained the same number of calories, with the only difference being the source of fat.

The diets were designed to reflect common patterns of fat consumption in the modern American diet.

According to Ruiz, many earlier studies relied on a simpler approach.

For decades, researchers commonly ‘gave mice very high levels of fat in their diet, often using a single fat source.’ In many cases, those diets derived 60% of calories from lard, which does not accurately reflect typical human eating habits and makes it difficult to determine the effects of individual fatty acids.

Exactly what components of dietary fat cause cancer has remained a mystery, Ruiz adds.

Implications for Cancer Prevention

The research has not yet been replicated in humans, but the findings may be especially relevant for people at elevated risk of pancreatic cancer.

Those at risk include individuals with chronic pancreatitis, obesity, late-onset diabetes, or a family history of the disease.

According to Ruiz, the study begins to shed light on how we might address the question of what changes in diet can help prevent cancer.

Looking ahead, the researchers plan to investigate whether adjusting dietary fat composition could improve outcomes for people who already have pancreatic cancer.

They also want to explore whether the ratio of MUFAs to PUFAs in the bloodstream could serve as an early warning marker for pancreatic cancer risk.