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Mediterranean Diet & Breast Cancer

Association with reduced invasive BC risk

Publish date:: February 9, 2016

There were beneficial effects of a Mediterranean diet supplemented with extra-virgin olive oil in the primary prevention of breast cancer in an evaluation of the effects of 2 interventions with Mediterranean diet vs the advice to follow a low-fat diet. In this study, 4,282 women aged 60 to 80 years and at high cardiovascular disease risk were randomized 1:1:1 to a Mediterranean diet supplemented with extra-virgin olive oil, a Mediterranean diet supplemented with mixed nuts, or a control diet (advice to reduce dietary fat). Breast cancer incidence was a prespecified second outcome for 4,152 women without a prior history of breast cancer. After a median follow-up of 4.8 years, researchers found:

• There were 35 confirmed incident cases of breast cancer.

• Observed rates (per 1,000 person-years) were 1.1 for the Mediterranean diet with extra-virgin olive oil group, 1.8 for the Mediterranean diet with nuts group, and 2.9 for the control group.

• The multivariable adjusted hazard ratios vs the control group were 0.32 for the Mediterranean diet with extra-virgin olive oil group and 0.59 for the Mediterranean diet with nuts group.

Citation: Toledo E. Salas-Salvadó, Donat-Vargas C, et al. Mediterranean diet and invasive breast cancer risk among women at high cardiovascular risk in the PREIMED Trial: A randomized clinical trial. JAMA Intern Med. 2015;175(11):1752-1760. doi: 10.1001/jamainternmed.2015.4838.

Commentary: Lifestyle, specifically diet and exercise, can have profound effects upon the development of cancer. It is estimated that one-third of the more than 572,000 cancer deaths that occur in the US each year can be attributed to diet and physical activity habits.¹ Individuals with high levels of physical activity have approximately 30% less breast cancer than women with low levels of exercise. Epidemiologic studies have shown that breast cancer incidence is lower in Mediterranean countries than in other European countries, raising the possibility of the influence of the Mediterranean diet. The physiologic rationale for an influence of extra-virgin olive oil on cancer is that this oil has anti-inflammatory and antioxidant polyphenols, whereas refined olive oil does not.² Earlier, smaller studies have shown a decrease in breast cancer with use of the Mediterranean diet, and this study further supports this relationship. An emerging approach to the primary prevention of breast cancer is following a Mediterranean diet with extra-virgin olive oil and regular exercise. —Neil Skolnik, MD

1. Kushi LH, Doyle C, McCullough M, et al. American cancer society guidelines on nutrition and physical activity for cancer prevention: reducing the risk of cancer with healthy food choices and physical activity. CA Cancer J Clin 2012;62(1):30–67. doi: 10.3322/caac.20140.

2. Moreno-Luna R, Muñoz-Hernandez R, Miranda ML, et al. Olive oil polyphenols decrease blood pressure and improve endothelial function in young women with mild hypertension. Am J Hypertens. 2012;25(12):1299-1304. doi: 10.1038/ajh.2012.128.

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