Intended for healthcare professionals

CCBYNC Open access
Research

Intake of fish and marine n-3 polyunsaturated fatty acids and risk of breast cancer: meta-analysis of data from 21 independent prospective cohort studies

BMJ 2013; 346 doi: https://doi.org/10.1136/bmj.f3706 (Published 27 June 2013) Cite this as: BMJ 2013;346:f3706

Re: Intake of fish and marine n-3 polyunsaturated fatty acids and risk of breast cancer: meta-analysis of data from 21 independent prospective cohort studies

Dear Dr. Schätzler,

Thank you for your questions. We draw our conclusions based on what was observed and found in the available data from our study. It may be true that very high intake of marine n-3 PUFA is not beneficial for breast cancer. Yet, this was not shown to be the case in our present study (1). In the particular range of n-3 PUFA intake in our included studies, we have observed a significant inverse dose-response relationship between marine n-3 PUFA and risk of breast cancer.

Dose-response analysis found no association with risk of breast cancer per 15 g/day increment of fish intake (relative risk 1.00, 95% confidence interval 0.97 to 1.03). Therefore, your comment “Only those with "15 g/day increment of fish intake" consumption had the lowest incidental outcome of breast cancer” is not consistent with the findings of our study.

"dose-response analyses indicated a 5% lower risk of breast cancer per 0.1g/day or 0.1% energy/day increment of dietary marine n-3 PUFA" does not suggest that daily intake of 2.0 gram of marine n-3 PUFA could reduce the risk of breast cancer by 100 percent. Within the range of marine n-3 PUFA intake among our included studies, this dose-response linear association does exist. However, with higher or lower marine n-3 PUFA intake, this linear association may not be true, as indicated in our observed curvilinear dose-response relationship for marine n-3 PUFA (% energy/d) and breast cancer risk. In any case, our conclusions are based on all the available data in the included prospective studies. We acknowledge that more work is necessary to examine the relationships.

References:
Intake of fish and marine n-3 polyunsaturated fatty acids and risk of breast cancer: meta-analysis of data from 21 independent prospective cohort studies. Zheng JS, Hu XJ, Zhao YM, Yang J, Li D. BMJ 2013;346:f3706.

Competing interests: No competing interests

15 August 2013
Ju-Sheng Zheng
Nutritionist
Duo Li
Department of Food Science and Nutrition, Zhejiang University
866 Yu-hang-tang Rd, Hangzhou, China