Emerging research continues to spotlight the potential role of diet in cancer prevention, with olive oil—a cornerstone of the Mediterranean diet—at the forefront of interest. A recent study published in the European Journal of Cancer drew from the well-regarded Moli-sani cohort and explored the relationship between olive oil intake and breast cancer (BC) risk.
Olive oil is rich in bioactive compounds, most notably monounsaturated fats (MUFAs) like oleic acid, and phenolic compounds such as hydroxytyrosol, tyrosol, and oleuropein. These components have demonstrated significant anti-inflammatory, antioxidant, and anti-proliferative properties in experimental studies. Oleic acid, which makes up the bulk of olive oil’s fat content, has been shown to reduce inflammation, lower cholesterol, and regulate blood pressure. More importantly, it may inhibit cancer-promoting signaling pathways and suppress tumor growth.
Phenolic compounds in olive oil further enhance its protective profile. Hydroxytyrosol and oleuropein, for instance, have shown antitumor activity in both in vitro and in vivo models. These polyphenols can influence gene expression related to cell proliferation, apoptosis (programmed cell death), DNA repair, and oxidative stress—all of which are critical in cancer prevention and progression.
Breast cancer is a heterogeneous disease, and its risk factors—and response to diet—can vary depending on tumor subtype. Hormone receptor-positive (ER+/PR+) cancers are heavily influenced by estrogen, which may dampen the measurable impact of dietary factors. In contrast, hormone receptor-negative (ER–, HER2–) tumors may be more responsive to environmental and nutritional influences, given the absence of strong hormonal drivers. The study noted a particularly interesting inverse association between olive oil consumption and ER– and HER2– breast cancers. These subtypes are often more aggressive and harder to treat, making any potential preventive strategy especially valuable. One compound, oleuropein aglycone, has been shown to suppress HER2 gene expression in human breast cancer cells, offering a mechanistic explanation for the observed protective effects.
Additionally, while literature on progesterone receptor-positive (PR+) tumors remains limited, this study found a reduced risk associated with olive oil consumption in women with PR+ breast cancer. This novel finding suggests new avenues for research, especially given the lack of existing data on PR+ tumors independently.
Despite promising findings, the study is not without limitations. The Moli-sani cohort study is observational, which precludes any firm conclusions about causality. Dietary intake data were self-reported, introducing potential for recall and measurement bias. Furthermore, the number of cases for specific tumor subtypes was limited, reducing statistical power. The systematic review component, although comprehensive, also included case-control studies that may suffer from post-diagnosis recall bias. Additionally, the findings may not be universally applicable due to geographical and lifestyle differences, including varying baseline diets, genetic factors, and health behaviors.
Given the strong biological plausibility and initial epidemiological support, future research must build on these findings with well-designed randomized controlled trials (RCTs) and large-scale cohort studies. These should focus on dose-response relationships, account for hormone receptor status, and utilize standardized tools to measure olive oil intake across diverse populations.
If confirmed, the protective association between olive oil and hormone receptor–negative breast cancer could have significant public health implications. Olive oil, as part of a balanced diet, may become a strategic component in dietary recommendations aimed at cancer prevention—not only in Mediterranean countries, but globally.
Sources: European Journal of Cancer
