People used to think that eating less fat would lower the chance of getting cancer. New studies say the story is more complex.
Researchers looked at pancreatic cancer, a very deadly disease. They found that the kind of fat matters more than the total amount.
Olive‑Oil Fat May Speed Up Tumors
The team discovered a surprising link between oleic acid – the main fat in olive oil – and faster tumor growth. Olive‑oil fat is usually called “good” for the heart, but it seemed to help pancreatic tumors grow in mice.
Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer. Only about 13 % of patients survive five years after diagnosis.
Testing Many Fat Types
To see how each fat works, scientists made twelve high‑fat diets. All diets had the same calories; only the fat source changed. The diets reflected what many Americans eat today.
Older experiments often gave mice one single fat, like lard, at very high levels. That does not match real‑world eating habits, so it was hard to know which fats mattered.
Bad Fat vs. Good Fat
Mice with a gene that causes cancer grew tumors faster when their diet was rich in oleic acid. Oleic acid is a monounsaturated fat (MUFA) found in olive oil, certain sunflower oils, peanuts, and lard.
When the diet was high in polyunsaturated fats (PUFAs), especially omega‑3s from fish oil, tumor growth slowed. Mice fed fish‑oil diets had about half the disease compared with those on a regular fat diet.
Why Some Fats Help Cancer Cells
Scientists studied a process called ferroptosis – a way cells die when their fats get oxidized. PUFAs are easy to oxidize, so they make cancer cells more likely to die. MUFAs resist oxidation, protecting cancer cells from ferroptosis.
When the researchers increased the MUFA‑to‑PUFA ratio, cancer got worse. Lowering that ratio improved outcomes.
Sex Differences in Mice
The harmful effect of oleic acid showed up mainly in male mice. Female mice did not show the same increase. Both sexes benefited from PUFA‑rich diets.
What This Could Mean for People
Human studies are still needed, but the findings could matter for people at high risk of pancreatic cancer – such as those with chronic pancreatitis, obesity, late‑onset diabetes, or a family history.
Doctors often get asked, “What can I change in my diet to lower cancer risk?” This research gives a clue: the type of fat you eat might be a key factor.
Future work will test if changing fat types can help patients who already have pancreatic cancer and whether blood levels of MUFAs and PUFAs could predict risk.