Olive oil consumption and risk of breast cancer: Prospective results from the Moli-sani Study, and a

Olive oil consumption and risk of breast cancer: Prospective results from the Moli-sani Study, and a systematic review of observational studies and randomized clinical trials

Emilia Ruggiero∙ Sukshma Sharma∙ Augusto Di Castelnuovo∙ Simona Costanzo∙ Teresa Panzera∙ Simona Esposito∙ Chiara Cerletti∙ Maria Benedetta Donati∙ Giovanni de Gaetano∙ Licia Iacoviello∙ Marialaura Bonaccio∙

Originally published in the European Journal of Cancer
DOI: 10.1016/j.ejca.2025.115520

Highlights

• Higher olive oil intake was linked to lower risk of hormone receptor-negative BC.

• No clear association found between olive oil and overall breast cancer risk.

• Risk of ER-negative breast cancer was reduced with increased olive oil consumption.

• A systematic review found mixed results across study types and designs.

• Case-control studies and one RCT suggested olive oil may offer protection.

Abstract

Background

Breast cancer (BC) is the leading cause of cancer-related death among women worldwide. Olive oil, rich in monounsaturated fats and polyphenols, has been linked to a reduced BC risk, but epidemiological evidence remains limited. This study examined the association between olive oil consumption and BC risk in a large cohort of adult Italian women and conducted a systematic review on this association.

Methods

Longitudinal analyses were performed on 11,442 women (mean age 54.7 ± 11.6 years) enrolled in the Moli-sani Study (2005–2010). Cox proportional hazard models were used to estimate BC risk in relation to olive oil consumption. A systematic review was conducted by searching Scopus, EMBASE, PubMed, and MEDLINE databases up to October 2024 for observational studies and RCTs.

Results

Compared with lower olive oil consumption (≤2 tbsp./day), multivariable-adjusted HRs associated with highest intake (>3 tbsp./d) for overall, premenopausal, and postmenopausal BC were 0.71(95 %CI 0.48–1.05), 0.80 (95 %CI 0.28–2.28), and 0.70 (95 %CI 0.46–1.08), respectively.

An increase of 1-tbsp./d of olive oil was associated with a lower risk of ER and PR breast cancers (HR=0.32; 95 %CI 0.13–0.77), particularly ER cases (HR=0.32; 95 %CI 0.15–0.69); additionally, a lowered hazard of HER2– BC incidence was observed at highest consumption of olive oil compared to the bottom category (HR=0.54; 95 %CI 0.31–0.96).

The systematic review included 13 observational studies (11 case-control and 2 prospective) and 1 RCT. While case-control studies and the RCT suggested a protective effect associated with olive oil consumption, longitudinal studies reported no association.

Conclusions

Findings from the Moli-sani Study suggest an inverse association between olive oil consumption and the risk of hormone receptor-negative breast cancers, particularly ER subtype, while results were inconclusive for overall BC risk. The systematic review revealed that case-control studies more frequently reported a protective association, whereas prospective studies did not consistently support this finding.