Among women, breast tumors rank as the leading cause of death from cancer. 

And the National Cancer Institute estimates that one out of every eight woman born in the U.S. will develop some form of the disease. 

 Although genes can be decisive, population studies suggest that diet and lifestyle help determine a woman's risk of breast cancer. 

Fat intakes may be linked to breast cancer, and the influence of various dietary fats on risk has been intensively studied. 

Animal tests and cell studies suggest that omega-3 fatty acids from fish hold the greatest potential to inhibit or curtail breast cancer. 

However, the results of studies that follow women's diets and health over time have been inconsistent with regard to the influence of dietary omega-3s. 

Recently, a Chinese team set out to clarify the state of the evidence by performing a “meta-analysis” of the available studies. 

Chinese evidence review sees benefit from fish-source omega-3s 
Scientists from China's Zhejiang University investigated the links between dietary omega-3s and the risk of breast cancer (Zheng J et al. 2013). 

They analyzed data from 21 U.S., European, and Asian studies involving 883,585 participants, more than 20,000 of whom developed breast cancer. 

Some of the studies recorded women's intakes of seafood, in order to estimate their omega-3 intakes … while other studies measured women's omega-3 blood levels. 

The Chinese team's analysis showed that women who consumed the most seafood -source omega-3s were 14 percent less likely to develop breast cancer. 

Importantly, the analysis detected a “dose-response” relationship, which strengthens the credibility of the apparent association between higher omega-3 intakes and lower breast cancer risk. 

Specifically, women's risk for breast cancer dropped by five percent for every 0.1 grams of omega-3s they consumed daily. 

Likewise, women's breast cancer risk dropped by five percent for every 0.1 percent of daily calories obtained from dietary omega-3s. 

The authors estimated that women would need to eat one to two portions of fish per week to achieve a 14 percent drop in risk. 

In contrast to seafood-source omega-3s, the analysis found no benefit from higher intakes of the sole plant-source omega-3, known as ALA (alpha-linolenic acid). 

(Omega-3 ALA is concentrated in flaxseed oil, walnuts, flaxseed, walnut oil, canola oil, and dark, leafy greens such as spinach, kale, chard, and collards). 

The authors said that together with previous publications, their analysis “supports a protective role of marine [seafood-source] omega-3s on the incidence of breast cancer.” 

As they concluded, “Our present study provides solid and robust evidence that marine omega-3s are inversely associated with risk of breast cancer. The protective effect of fish or individual omega-3 fatty acids warrants further investigation ...”. (Zheng J et al. 2013) 

The study was funded by the National Natural Science Foundation of China, Ministry of Education of China, and National Basic Research Program of China. 

  • British Medical Journal (BMJ). Fatty acids found in fish linked to lower risk of breast cancer. June 27, 2013. Accessed at
  • Engeset D et al. Fish consumption and breast cancer risk. The European Prospective Investigation into Cancer and Nutrition (EPIC). Int J Cancer. 2006 Jul 1;119(1):175-82. 
  • Gago-Dominguez M, Yuan JM, Sun CL, Lee HP, Yu MC. Opposing effects of dietary n-3 and n-6 fatty acids on mammary carcinogenesis: The Singapore Chinese Health Study. Br J Cancer. 2003 Nov 3;89(9):1686-92. 
  • Murff HJ, Shu XO, Li H, Yang G, Wu X, Cai H, Wen W, Gao YT, Zheng W. Dietary polyunsaturated fatty acids and breast cancer risk in Chinese women: a prospective cohort study. Int J Cancer. 2011 Mar 15;128(6):1434-41. doi: 10.1002/ijc.25703. Epub 2010 Nov 23. 
  • Patterson RE, Flatt SW, Newman VA, Natarajan L, Rock CL, Thomson CA, Caan BJ, Parker BA, Pierce JP. Marine fatty acid intake is associated with breast cancer prognosis. J Nutr. 2011 Feb;141(2):201-6. doi: 10.3945/jn.110.128777. Epub 2010 Dec 22. 
  • Zheng J et al. 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: Accessed at