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BMJ. 2014 Jun 10;348:g3437. doi: 10.1136/bmj.g3437.

Dietary protein sources in early adulthood and breast cancer incidence: prospective cohort study.

Author information

1
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.
2
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.
3
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.
4
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.
5
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.

Abstract

OBJECTIVE:

To investigate the association between dietary protein sources in early adulthood and risk of breast cancer.

DESIGN:

Prospective cohort study.

SETTING:

Health professionals in the United States.

PARTICIPANTS:

88,803 premenopausal women from the Nurses' Health Study II who completed a questionnaire on diet in 1991.

MAIN OUTCOME MEASURE:

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).

CONCLUSION:

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.

PMID:
24916719
PMCID:
PMC4051890
[Indexed for MEDLINE]
Free PMC Article

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