Intake of fish and marine n-3 polyunsaturated fatty acids and risk of breast cancer: meta-analysis of data from 21 independent prospective cohort studiesBMJ 2013; 346 doi: https://doi.org/10.1136/bmj.f3706 (Published 27 June 2013) Cite this as: BMJ 2013;346:f3706
- Ju-Sheng Zheng, PhD student12,
- Xiao-Jie Hu, PhD student12,
- Yi-Min Zhao, masters student12,
- Jing Yang, PhD student12,
- Duo Li, professor12
- 1Department of Food Science and Nutrition, Zhejiang University, Hangzhou 310058, China
- 2APCNS Center of Nutrition and Food Safety, Hangzhou 310058, China
- Correspondence to: D Li, Department of Food Science and Nutrition, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China
- Accepted 31 May 2013
Objectives To investigate the association between intake of fish and n-3 polyunsaturated fatty acids (n-3 PUFA) and the risk of breast cancer and to evaluate the potential dose-response relation.
Design Meta-analysis and systematic review of prospective cohort studies.
Data sources PubMed and Embase up to December 2012 and references of retrieved relevant articles.
Eligibility criteria for selecting studies Prospective cohort studies with relative risk and 95% confidence intervals for breast cancer according to fish intake, n-3 PUFA intake, or tissue biomarkers.
Results Twenty six publications, including 20 905 cases of breast cancer and 883 585 participants from 21 independent prospective cohort studies were eligible. Eleven articles (13 323 breast cancer events and 687 770 participants) investigated fish intake, 17 articles investigated marine n-3 PUFA (16 178 breast cancer events and 527 392 participants), and 12 articles investigated alpha linolenic acid (14 284 breast cancer events and 405 592 participants). Marine n-3 PUFA was associated with 14% reduction of risk of breast cancer (relative risk for highest v lowest category 0.86 (95% confidence interval 0.78 to 0.94), I2=54), and the relative risk remained similar whether marine n-3 PUFA was measured as dietary intake (0.85, 0.76 to 0.96, I2=67%) or as tissue biomarkers (0.86, 0.71 to 1.03, I2=8%). Subgroup analyses also indicated that the inverse association between marine n-3 PUFA and risk was more evident in studies that did not adjust for body mass index (BMI) (0.74, 0.64 to 0.86, I2=0) than in studies that did adjust for BMI (0.90, 0.80 to 1.01, I2=63.2%). Dose-response analysis indicated that risk of breast cancer was reduced by 5% per 0.1g/day (0.95, 0.90 to 1.00, I2=52%) or 0.1% energy/day (0.95, 0.90 to 1.00, I2=79%) increment of dietary marine n-3 PUFA intake. No significant association was observed for fish intake or exposure to alpha linolenic acid.
Conclusions Higher consumption of dietary marine n-3 PUFA is associated with a lower risk of breast cancer. The associations of fish and alpha linolenic acid intake with risk warrant further investigation of prospective cohort studies. These findings could have public health implications with regard to prevention of breast cancer through dietary and lifestyle interventions.
We thank Laurence D Parnell at Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University for helping to edit the manuscript.
Contributors: J-SZ and DL conceived the study. J-SZ and X-JH searched the databases and checked them according to the eligible criteria and exclusion criteria. DL helped develop search strategies. J-SZ analysed the data and wrote the draft of the paper. All authors contributed to writing, reviewing, or revising the paper. DL is guarantor.
Funding: This study was funded by National Natural Science Foundation of China (NSFC, No 81273054), the PhD. Programs Foundation of Ministry of Education of China (20120101110107), and the National Basic Research Program of China (973 Program 2011CB504002). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.
Ethical approval: Not required.
Data sharing: No additional data available.
This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 3.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/3.0/.