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JAMA Intern Med. 2015 Nov;175(11):1752-60. doi: 10.1001/jamainternmed.2015.4838.

Mediterranean Diet and Invasive Breast Cancer Risk Among Women at High Cardiovascular Risk in the PREDIMED Trial: A Randomized Clinical Trial.

Author information

1
Department of Preventive Medicine and Public Health, University of Navarra-School of Medicine, Pamplona, Navarra, Spain2Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain.
2
Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain3Human Nutrition Unit, Faculty of Medicine and Health Sciences, Biochemistry Biotechnology Department, Universitat Rovira i Vir.
3
Servicio Navarro de Salud-Osasunbidea, Pamplona, Navarra, Spain5IdiSNA, Navarra Institute for Health Research, Pamplona, Navarra, Spain.
4
Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain6Department of Internal Medicine, Institut d'Investigacions Biomèdiques August Pi I Sunyer, Hospital Clinic, University of Barc.
5
Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain7Lipid Clinic, Department of Endocrinology and Nutrition, Institut d'Investigacions Biomèdiques August Pi I Sunyer, Hospital Cl.
6
Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain8Department of Preventive Medicine, University of Valencia, Valencia, Spain.
7
Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain9Cardiovascular and Nutrition Research Group, Institut de Recerca Hospital del Mar, Barcelona, Spain.
8
Departments of Nutrition and Epidemiology, Harvard School of Public Health, Boston, Massachusetts11Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts.
9
Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain12University Hospital of Alava, Vitoria, Basque Country, Spain.
10
Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain13Department of Preventive Medicine, University of Malaga, Malaga, Spain.
11
Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain14Instituto de Investigación Sanitaria de Palma (IdISPa), Hospital Universitario Son Espases, Palma de Mallorca, Spain.
12
Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain15Department of Family Medicine, Primary Care Division of Sevilla, Sevilla, Spain.
13
Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain16Research Institute of Biomedical and Health Sciences, University of Las Palmas de Gran Canaria, Las Palmas, Spain.
14
Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain17Lipids and Vascular Risk Unit, Internal Medicine, Hospital Universitario de Bellvitge-IDIBELL-UB, Hospitalet de Llobregat, Ba.
15
Primary Care Division of Barcelona, Institut Català de la Salut and IDiap-Jordi Gol, Barcelona, Spain19Centro de Investigación Biomédica en Red Epidemiología y Salud Pública, Instituto de Salud Carlos III, Madrid, Spain.
16
Centro de Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain5IdiSNA, Navarra Institute for Health Research, Pamplona, Navarra, Spain.

Abstract

IMPORTANCE:

Breast cancer is the leading cause of female cancer burden, and its incidence has increased by more than 20% worldwide since 2008. Some observational studies have suggested that the Mediterranean diet may reduce the risk of breast cancer.

OBJECTIVE:

To evaluate the effect of 2 interventions with Mediterranean diet vs the advice to follow a low-fat diet (control) on breast cancer incidence.

DESIGN, SETTING, AND PARTICIPANTS:

The PREDIMED study is a 1:1:1 randomized, single-blind, controlled field trial conducted at primary health care centers in Spain. From 2003 to 2009, 4282 women aged 60 to 80 years and at high cardiovascular disease risk were recruited after invitation by their primary care physicians.

INTERVENTIONS:

Participants were randomly allocated 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).

MAIN OUTCOMES AND MEASURES:

Breast cancer incidence was a prespecified secondary outcome of the trial for women without a prior history of breast cancer (n = 4152).

RESULTS:

After a median follow-up of 4.8 years, we identified 35 confirmed incident cases of breast cancer. Observed rates (per 1000 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 (95% CI, 0.13-0.79) for the Mediterranean diet with extra-virgin olive oil group and 0.59 (95% CI, 0.26-1.35) for the Mediterranean diet with nuts group. In analyses with yearly cumulative updated dietary exposures, the hazard ratio for each additional 5% of calories from extra-virgin olive oil was 0.72 (95% CI, 0.57-0.90).

CONCLUSIONS AND RELEVANCE:

This is the first randomized trial finding an effect of a long-term dietary intervention on breast cancer incidence. Our results suggest a beneficial effect of a Mediterranean diet supplemented with extra-virgin olive oil in the primary prevention of breast cancer. These results come from a secondary analysis of a previous trial and are based on few incident cases and, therefore, need to be confirmed in longer-term and larger studies.

TRIAL REGISTRATION:

ISRCTN.org Identifier: ISRCTN35739639.

PMID:
26365989
DOI:
10.1001/jamainternmed.2015.4838
[Indexed for MEDLINE]
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