title: Dietary protein sources in early adulthood and breast cancer incidence: prospective cohort study.
abstract: OBJECTIVE
  To investigate the association between dietary protein sources in early adulthood and risk of breast cancer.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  Health professionals in the United States.
  
  
  METHODS
  88,803 premenopausal women from the Nurses' Health Study II who completed a questionnaire on diet in 1991.
  
  
  METHODS
  Incident cases of invasive breast carcinoma, identified through self report and confirmed by pathology report.
  
  
  RESULTS
  We documented 2830 cases of breast cancer during 20 years of follow-up. Higher intake of total red meat was associated with an increased risk of breast cancer overall (relative risk 1.22, 95% confidence interval 1.06 to 1.40; P(trend) = 0.01, for highest fifth v lowest fifth of intake). However, higher intakes of poultry, fish, eggs, legumes, and nuts were not related to breast cancer overall. When the association was evaluated by menopausal status, higher intake of poultry was associated with a lower risk of breast cancer in postmenopausal women (0.73, 0.58 to 0.91; P(trend) =0.02, for highest fifth v lowest fifth of intake) but not in premenopausal women (0.93, 0.78 to 1.11; P(trend) = 0.60, for highest fifth v lowest fifth of intake). In estimating the effects of exchanging different protein sources, substituting one serving/day of legumes for one serving/day of red meat was associated with a 15% lower risk of breast cancer among all women (0.85, 0.73 to 0.98) and a 19% lower risk among premenopausal women (0.81, 0.66 to 0.99). Also, substituting one serving/day of poultry for one serving/day of red meat was associated with a 17% lower risk of breast cancer overall (0.83, 0.72 to 0.96) and a 24% lower risk of postmenopausal breast cancer (0.76, 0.59 to 0.99). Furthermore, substituting one serving/day of combined legumes, nuts, poultry, and fish for one serving/day of red meat was associated with a 14% lower risk of breast cancer overall (0.86, 0.78 to 0.94) and premenopausal breast cancer (0.86, 0.76 to 0.98).
  
  
  CONCLUSIONS
  Higher red meat intake in early adulthood may be a risk factor for breast cancer, and replacing red meat with a combination of legumes, poultry, nuts and fish may reduce the risk of breast cancer.
authors.affiliation: Department of Nutrition, Harvard School of Public Health, Boston 02115, MA, USA Department of Community Nutrition, Faculty of Nutrition Sciences and Food Technology, Shahid Beheshti University of Medical Sciences, Tehran, Iran mfarvid@hsph.harvard.edu.
authors.forename: Maryam S
authors.initials: MS
authors.lastname: Farvid
authors.affiliation: Department of Dermatology, The Warren Alpert Medical School of Brown University, Providence, RI, USA Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA.
authors.forename: Eunyoung
authors.initials: E
authors.lastname: Cho
authors.affiliation: Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, USA.
authors.forename: Wendy Y
authors.initials: WY
authors.lastname: Chen
authors.affiliation: Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA.
authors.forename: A Heather
authors.initials: AH
authors.lastname: Eliassen
authors.affiliation: Department of Nutrition, Harvard School of Public Health, Boston 02115, MA, USA Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA.
authors.forename: Walter C
authors.initials: WC
authors.lastname: Willett
mesh_terms: D000328:Adult; D000367:Age Factors; D000818:Animals; D001943:Breast Neoplasms / Q000453:epidemiology*; D004044:Dietary Proteins; D005260:Female; D006801:Humans; D015994:Incidence; D011446:Prospective Studies; D018570:Risk Assessment; D055815:Young Adult
chemical_list: D004044:Dietary Proteins