As nutrition advice keeps pushing Americans toward unsaturated fats, new cancer research is drawing a sharper line between which ones may help and which ones may harm. This week, researchers reported that olive oil was linked to lower risk for several obesity-related cancers, while a separate study found linoleic acid, a common omega-6 fat in seed oils, may promote growth in triple-negative breast cancer. Together, the findings add new detail to a broad public health conversation that has often grouped “healthy fats” into one category.
One study linked linoleic acid to tumor growth
Researchers at Weill Cornell Medicine reported on July 23, 2025, that linoleic acid appears to help triple-negative breast cancer cells grow by activating a major growth pathway. The team said the fat binds to a protein called FABP5, which is found at high levels in triple-negative tumors, and that interaction can switch on mTORC1 signaling.
The study focused on triple-negative breast cancer, which accounts for about 15% of breast cancer cases, according to the researchers. In mouse experiments and blood sample analysis from patients, the team found higher linoleic acid levels were associated with tumor growth in this cancer subtype, but not in hormone-sensitive breast cancers.
The researchers said the findings do not show that seed oils broadly cause breast cancer. They stated that the effect appears tied to a specific disease subtype and a specific molecular mechanism, and they said more work is needed before any diet advice changes for the general public.
Another study found olive oil linked to lower cancer risk
In a separate report presented in July 2025, researchers analyzing data from more than 200,000 U.S. adults found that people with the highest olive oil intake had a lower risk of obesity-related cancers. The analysis tracked participants for more than 30 years and included repeated dietary questionnaires, according to the study team.
The reported benefit was strongest when olive oil replaced butter, margarine, or mayonnaise. Researchers said that swap was associated with lower risk of cancers tied to obesity, a group that includes postmenopausal breast, colorectal, liver, and pancreatic cancers.
This was an observational study, which means it found an association rather than proving cause and effect. Even so, the size of the cohort and the long follow-up period gave researchers a large data set to compare long-term eating patterns with later cancer outcomes.
What the findings mean for everyday diets
The two studies point to a more nuanced message than the standard advice to simply eat more unsaturated fat. The July 2025 lab study looked at one omega-6 fat, linoleic acid, in one aggressive cancer subtype, while the olive oil study examined long-term diet patterns across a much broader U.S. population.
What is confirmed is that these fats were not interchangeable in the research results. What is not yet known is whether reducing linoleic acid intake would change cancer outcomes in people, because the tumor-growth findings still need clinical testing in humans.
For consumers, the practical takeaway is still limited to what the researchers directly reported. Olive oil intake was associated with lower cancer risk in a large U.S. cohort, and linoleic acid showed a tumor-supporting mechanism in triple-negative breast cancer research, but neither study announced new national dietary guidelines as of July 23, 2025.
