This article is more than 5 years old. Information may no longer be current.
Mediterranean diet plus extra virgin olive oil may reduce breast cancer risk
Click Here to Manage Email Alerts
A Mediterranean diet supplemented with extra virgin olive oil may reduce the risk for breast cancer, according to results of a randomized trial conducted in Spain.
Diet has been identified as a modifiable risk factor for breast cancer in previous studies. However, studies of diet are often observational and can be confounded by the fact individuals do not consume foods in isolation.
Miguel Angel Martinez-Gonzalez, MD, MPH, PhD, chair of the department of preventive medicine and public health at University of Navarra Medical School in Pamplona, Spain, and colleagues conducted a randomized clinical trial to assess the impact a Mediterranean diet had on breast cancer risk as part of the PREDIMED trial, which tested the effects a Mediterranean diet had on the prevention of cardiovascular disease.
The researchers analyzed the effects of two interventions with the Mediterranean diet — a diet consisting of an abundance of plant foods, fish and olive oil. One arm of the study consisted of individuals who were given one liter per week of extra virgin olive oil for their household and the other arm was given 30 grams of mixed nuts (walnuts, hazelnuts and almonds) per day. A third arm — which consisted of women who were advised to reduce dietary fat — was used as a control.
The PREDIMED trial enrolled 4,282 women aged 60 to 80 years who were at high risk for cardiovascular disease between 2003 and 2009. The incidence of breast cancer served as a secondary outcome of the trial for women without a prior history of the disease (n = 4,152).
After a median follow-up of 4.8 years, there were 35 confirmed cases of breast cancer. The rate of breast cancer was 1.1 per 1,000 person-years in the extra virgin olive oil arm compared with 1.8 per 1,000 person-years for the nuts group and 2.9 per 1,000 person-years for the control group.
Results of a multivariable analysis adjusted for factors such as study site, BMI, alcohol consumption and age at menopause, a Mediterranean diet supplemented with extra virgin olive oil significantly decreased the risk for breast cancer compared with the control population (HR = 0.32; 95% CI, 0.13-0.79). The diet supplemented with nuts also reduced the risk for breast cancer, but this association did not reach statistical significance (HR = 0.59; 95% CI, 0.26-1.35).
In analyses with yearly cumulative updated dietary exposures, the HR for breast cancer risk for each additional 5% of calories from olive oil was 0.72 (95% CI, 0.57-0.9).
“Preventive strategies represent the most sensible approach against cancer,” Martinez-Gonzalez and colleagues wrote. “The intervention paradigm implemented in the PREDIMED trial provides a useful scenario for breast cancer prevention because it is conducted in primary health care centers and also offers beneficial effects on a wide variety of health outcomes.”
Limitations for these results include the small number of outcomes, that not all women were screened for breast cancer with a mammography, women were not blinded to dietary type, and that all women were white, postmenopausal and at high risk for cardiovascular disease.
Michael H. Katz, MD, a deputy editor at JAMA Internal Medicine, the journal in which the study was published, wrote that although he and his fellow editors aren’t usually intrigued by diet-related studies, they were impressed with this study because of its randomization and high-quality structure.
“Consumption of a Mediterranean diet … is known to reduce the risk of cardiovascular disease and is safe,” Katz wrote. “It may also prevent breast cancer. We hope to see more emphasis on Mediterranean diet to reduce cancer and cardiovascular disease and improve health and well-being.” – by Anthony SanFilippo
Disclosure: Toledo and Katz report no relevant financial disclosures. Please see the full study for a list of all other researchers’ relevant financial disclosures.
Click Here to Manage Email Alerts