How Diet Could Affect Breast Cancer Risk

Mediterranean diet high in olive oil linked to breast cancer risk reduction

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) The Mediterranean diet has long been promoted as a heart-healthy way of eating. But, for women, there may now be another good reason to adopt this diet.

A new study from Spain found that a Mediterranean diet with extra olive oil may decrease the risk of breast cancer in women.

In an editorial about this study, Deputy Editor of JAMA Internal Medicine Mitchell H. Katz. MD, wrote, "[The] consumption of a Mediterranean diet, which is based on plant foods, fish and extra virgin olive oil, is known to reduce the risk of cardiovascular disease and is safe. It may also prevent breast cancer."

While olives and olive oil are likely healthy, Raynelle Shelley, RD, LDN, a dietitian at Baylor Scott & White in Round Rock, TX, urged caution in interpreting these findings.

"I think it would be very misleading for the public to think that one single oil can single-handedly prevent cancer — it takes a well-rounded diet full of other nutrients and antioxidants to complement it," Shelley told dailyRx News. "We can consume all the olive oil we want but if we are still going through a drive-through twice a day or filling our grocery carts with 85 percent processed foods, then olive oil doesn't have a chance as a component of cancer prevention."

The Mediterranean diet is based on the traditional foods and drinks of the countries surrounding the Mediterranean Sea. It emphasizes plant-based foods, healthy fats like olive oil, herbs and spices to flavor food instead of salt, fish instead of red meat and red wine (in moderation).

For this study, a team of researchers led by Miguel A. Martínez-González, MD, an epidemiologist and nutrition researcher at the University of Navarra in Spain, looked at the potential effects of the Mediterranean diet on breast cancer risk.

These researchers drew data from the PREDIMED study, a long-term nutritional study that looked at the effects of the Mediterranean diet on heart disease.

Dr. Martínez-González and team divided 4,282 women with an average age of 68 into three groups.

The women in the first group ate a Mediterranean diet with extra olive oil. The women in the second group ate a Mediterranean diet with extra nuts. The women in the third group ate their regular diets, but were advised to reduce their fat intake.

Most of the women had gone through menopause before age 55. Less than 3 percent had used hormone therapy, which is known to increase breast cancer risk.

Because the PREDIMED study focused on heart disease, the women also had risk factors for heart disease, such as smoking or weight problems.

The women were followed from 2003 to 2009.

Those who ate the Mediterranean diet with extra olive oil had a 68 percent lower risk of breast cancer than those on the low-fat diet.

Those who ate the Mediterranean diet with nuts, however, only had a slightly lower risk of breast cancer compared to the low-fat group.

The study and editorial were published Sept. 14 in the journal JAMA Internal Medicine.

The National Institutes of Health, the Fondo de Investigación Sanitaria–Fondo Europeo de Desarrollo Regional and the Instituto de Salud Carlos III funded this research.

Olive oil and nuts were donated by Patrimonio Comunal Olivarero, Hojiblanca, the California Walnut Commission and La Morella Nuts.

Review Date: 
September 11, 2015
Last Updated:
September 18, 2015