Nutritional Pearls: Could the Mediterranean Diet Help Prevent Breast Cancer?
Mary is a 45-year-old woman who is worried about her risk of breast cancer. The disease runs in her family, and Mary is curious if there are any simple lifestyle changes she can make to lessen her risk.
How would you advise your patient?
(Answer and discussion on next page)
Dr. Gourmet is the definitive health and nutrition web resource for both physicians and patients with evidence-based resources including special diets for coumadin users, patients with GERD/acid reflux, celiac disease, type 2 diabetes, low sodium diets (1500 mg/d), and lactose intolerance.
Timothy S. Harlan, MD, is a board-certified internist and professional chef who translates the Mediterranean diet for the American kitchen with familiar, healthy recipes. He is an assistant dean for clinical services, executive director of The Goldring Center for Culinary Medicine, associate professor of medicine at Tulane University in New Orleans, faculty chair of the all-new Certified Culinary Medicine Specialist program, and co-chair of the Cardiometabolic Risk Summit.
Now, for the first time, Dr. Gourmet is sharing nutritional pearls of wisdom with the Consultant360 audience. Sign up today to receive an update from the literature each week.
Answer: A Mediterranean diet supplemented with olive oil can significantly reduce the risk of developing breast cancer.
In 2010, a long-term, large-scale study carried out in Greece looked at the relationship between women's Mediterranean diet score and their risk of breast cancer. Postmenopausal women with a score of at least 6 (out of 9 possible points) were 41% less likely to develop breast cancer than those with scores of 3 or less.
That's pretty big news by itself, but the study's weakness is that it was a prospective study: the participants' diets and other lifestyle factors were recorded at the start of the study, then at the end of the study the diets of those who developed breast cancer were compared to those who did not. The gold standard for research is still the controlled trial, in which one (or more) groups are assigned to an intervention and are then compared to a control group.
____________________________________________________________________________________________________________________________________________________________________
RELATED CONTENT
Breast Cancer Screening: At What Age to Stop?
Could the Mediterranean Diet Decrease Breast Cancer Risk?
____________________________________________________________________________________________________________________________________________________________________
The Research
In an ongoing study out of Spain known as PREDIMED (Prevención con Dieta Mediterránea), over 8000 men and women between 55 and 80 years old who were considered to be at high risk for cardiovascular disease were randomly assigned to 1 of 3 diets: a Mediterranean diet supplemented with a daily allotment of olive oil, a Mediterranean diet supplemented with a daily allotment of mixed nuts (walnuts, hazelnuts, and almonds), or a low-fat diet (the control diet). Regular visits with a dietitian helped the participants stick with their diets, although it should be noted that they were not specifically encouraged to reduce their caloric intake or to increase their amount of exercise.
After about 6 years, the researchers ended the trial early because the evidence they had amassed regarding heart disease risk was already unmistakeable. Since then, the study authors have continued analyzing the data to see what other effects a Mediterranean diet might have on health.
The Results
Recently, their newest findings were reported in JAMA Internal Medicine.1 For this analysis they limited themselves to the nearly 4300 women in the study, whose average age was ~68. Thirty-five women were diagnosed with malignant breast cancers over the course of the 5 years included in this part of the study, with 31 cases being estrogen-receptor positive and 21 cases being progesterone-receptor positive. (Not all cases reported receptor status of either type.)
Those women who were assigned to the Mediterranean diet supplemented with olive oil were 62% less likely to develop breast cancer than those on a control (low-fat) diet. Those who were assigned to the Mediterranean diet supplemented with nuts, however, saw no statistically significant difference from those in the control group. Grouping the 2 Mediterranean diets together, however, yielded a 51% reduction in risk of breast cancer compared to those on the control diet.
Intrigued by these results, the authors looked at olive oil intake more closely and found that those women who consumed at least 15% of their daily calories from olive oil enjoyed the greatest reduction in risk of breast cancer.
What’s The “Take Home”?
For an 1,800 calorie per day diet, 15% of calories from olive oil is 270 calories, or 5-7 teaspoons of olive oil (depending on the calories in the oil). That olive oil doesn't have to be drizzled on salads—that intake includes olive oil you saute with or that appears in other foods.
Don't make the mistake of assuming that it's the olive oil alone that protects women from breast cancer—the authors themselves note that people don't consume foods or nutrients in isolation, and this study was designed to evaluate a Mediterranean diet supplemented with olive oil or nuts. Improving your Mediterranean diet score by just 2 points over the long term can reduce your risk of death from all causes by 25%.
Reference:
Toledo E, Salas-Salvado J, Donat-Vargas C, et al. Mediterranean diet and invasive breast cancer risk among women at high cardiovascular risk in the predimed trial. JAMA Intern Med. 2015 September 14 [epub ahead of print]. doi:10.1001/jamainternmed.2015.4838.