Evidence that the omega-3 fats in fish tend to discourage cancer growth continues to mount.
People use the two “long-chain” omega-3s found in fish (EPA and DHA) in their cell membranes for critical immune, brain, eye, and metabolic functions.
They must either get EPA and DHA from fish and/or fish oil, or make them (very inefficiently) from the small amounts of the “short-chain” omega-3 (ALA) found in certain plant foods.
For more on this topic, see our Omega-3 Facts & Sources page.
Cancer risk tied to America’s omega imbalance
Last year, scientists from Penn State University College of Medicine analyzed the existing cell, animal, and population studies … and concluded that omega-3s generally discourage breast cancer.
As they wrote, “preclinical data have been, in general, more supportive of a protective effect of omega-3 fatty acids on breast cancer …”. (Signori C et al. 2011)
And accumulating evidence suggests that the “omega imbalance” in the standard American diet may be an even bigger problem.
For example, a study of 56,007 French women found breast cancer risk lowest among those whose estimated omega-3 intake placed in the top one-fifth.
And the authors found the risk of breast cancer highest among the women whose estimated omega-6 intake placed in the top one-fifth (Thiébaut AC et al. 2009).
This was just one of a number of population studies indicating that cancer risk is raised by imbalanced intakes of omega-3s and omega-6s ... as much or more than by diets low in omega-3s (Chajes V et al. 2002; Saadatian-Elahi M et al. 2002; Goodstine SL et al. 2003; Kuriki K et al. 2007; Shannon J et al. 2007; Sonestedt E et al. 2008; Bougnoux P et al. 2009).
To review some of this research, see “Breast Cancer and Omega-3s: More Encouraging Evidence”, “Breast Cancer Linked to Low Vitamin D and Omega-3 Levels”, and “Omega-3s May Fight Breast Cancer Fatigue”.
The studies that haven’t detected a protective effect from dietary omega-3s have generally failed to take omega-6 intake into account … and thereby do a serious disservice.
We covered this glaring flaw in study design – and some savvy researchers’ recognition of it – in “Breast Cancer Study Questions Omega-3s’ Preventive Power but Overlooks Context”.
Now, scientists have again linked increased breast cancer risk to diets providing too few omega-3s in relation to omega-6s.
And their study added important details about the varying effects of omega imbalances among obese, lean, and premenopausal women.
International study links breast cancer to the omega imbalance
Researchers from International Agency for Research on Cancer in Lyon, France conducted a “case-control” study among 2,074 premenopausal Mexican women (Maillard V et al. 2012).
Among these women, 1,000 had breast cancer and 1,074 were cancer-free “controls”, matched to the cancer cases by age, health care system, and region.
The results supported those of prior studies, and added nuances:
Overall, there was no link between higher omega-3 intake and reduced breast cancer risk.
Higher omega-3 intakes were linked to a 42 percent drop in breast cancer risk among obese women.
Higher omega-6 intakes were linked to a 92 percent rise in breast cancer risk among obese and lean women.
Higher omega-3 intakes were not linked to a lower risk of breast cancer among normal-weight or overweight women.
Obesity is defined as having a body mass index (BMI) of 30 kg/m2, overweight is defined as a BMI of 25 to 29.9 kg/m2 and normal body weight is defined as a BMI between 18.5 and 25 kg/m2.
The researchers came to these conclusions (Maillard V et al. 2012):
“Obesity status may affect the association between omega-3 intake and breast cancer risk. The underlying mechanisms may be related to decreased inflammation and improved adipokine and estrogen levels induced by omega-3 [content] in adipose tissue in obese women.”
(Adipokines – such as adiponectin, leptin, and resistin – are hormone-like signaling proteins secreted by fatty adipose tissue. They play crucial roles in promoting or suppressing appetite and fat accumulation.)
And they offered some logical advice: “Increased intake of omega-3 polyunsaturated fatty acids should be recommended [in women] … in particular in obese women.” (Maillard V et al. 2012)
We hope that public health officials and the media will begin to echo that precautionary advice … which appears risk-free and would yield ancillary heart, eye, and brain health benefits.
Leading researchers into the roles of dietary fatty acids – such as William Lands, Ph.D., Joe Hibbeln, M.D., and the late, great Ralph Holman, Ph.D. – agree that the existing evidence points to an inescapable conclusion.
The risks of the standard American diet stem as much from its extreme “omega imbalance> http://vitalchoice.com/shop/pc/viewPrd.asp?idproduct=1421&idcategory=756 <” as its excess of sugars, starches, and processed/refined foods.
To learn more, see “America’s Sickening ‘Omega Imbalance’”, our Omega-3/6 Balance page, and the Omega-3 / Omega-6 Balance section of our news archive.
Alfano CM, Imayama I, Neuhouser ML, Kiecolt-Glaser JK, Wilder Smith A, Meeske K, McTiernan A, Bernstein L, Baumgartner KB, Ulrich CM, Ballard-Barbash R. Fatigue, Inflammation, and ω-3 and ω-6 Fatty Acid Intake Among Breast Cancer Survivors. J Clin Oncol. 2012 Mar 12. [Epub ahead of print]
Baracos VE, Mazurak VC, Ma DW. n-3 Polyunsaturated fatty acids throughout the cancer trajectory: influence on disease incidence, progression, response to therapy and cancer-associated cachexia. Nutr Res Rev. 2004 Dec;17(2):177-92.
Bougnoux P, Hajjaji N, Maheo K, Couet C, Chevalier S. Fatty acids and breast cancer: sensitization to treatments and prevention of metastatic re-growth. Prog Lipid Res. 2010 Jan;49(1):76-86. Epub 2009 Aug 26. Review.
Goodstine SL, Zheng T, Holford TR, Ward BA, Carter D, Owens PH, Mayne ST. Dietary (n-3)/(n-6) fatty acid ratio: possible relationship to premenopausal but not postmenopausal breast cancer risk in U.S. women. J Nutr. 2003 May;133(5):1409-14.
Kuriki K, Hirose K, Wakai K, Matsuo K, Ito H, Suzuki T, Hiraki A, Saito T, Iwata H, Tatematsu M, Tajima K. Breast cancer risk and erythrocyte compositions of n-3 highly unsaturated fatty acids in Japanese. Int J Cancer. 2007 Jul 15;121(2):377-85.
Maillard V, Bougnoux P, Ferrari P, Jourdan ML, Pinault M, Lavillonniere F, Body G, Le Floch O, Chajès V, Torres-Mejía G, Biessy C, Ortega-Olvera C, Angeles-Llerenas A, Ferrari P, Lazcano-Ponce E, Romieu I. ω-3 and ω-6 Polyunsaturated fatty acid intakes and the risk of breast cancer in Mexican women: impact of obesity status. Cancer Epidemiol Biomarkers Prev. 2012 Feb;21(2):319-26. Epub 2011 Dec 22. doi:10.1158/1055-9965
Chajes V. N-3 and N-6 fatty acids in breast adipose tissue and relative risk of breast cancer in a case-control study in Tours, France. Int J Cancer. 2002 Mar 1;98(1):78-83.
Saadatian-Elahi M, Toniolo P, Ferrari P, Goudable J, Akhmedkhanov A, Zeleniuch-Jacquotte A, Riboli E. Serum fatty acids and risk of breast cancer in a nested case-control study of the New York University Women's Health Study. Cancer Epidemiol Biomarkers Prev. 2002 Nov;11(11):1353-60.
Sala-Vila A, Calder PC. Update on the relationship of fish intake with prostate, breast, and colorectal cancers. Crit Rev Food Sci Nutr. 2011 Oct-Nov;51(9):855-71. Review.
Shannon J, King IB, Moshofsky R, Lampe JW, Gao DL, Ray RM, Thomas DB.Erythrocyte fatty acids and breast cancer risk: a case-control study in Shanghai, China.Am J Clin Nutr. 2007 Apr;85(4):1090-7.
Signori C, El-Bayoumy K, Russo J, Thompson HJ, Richie JP, Hartman TJ, Manni A. Chemoprevention of breast cancer by fish oil in preclinical models: trials and tribulations. Cancer Res. 2011 Oct 1;71(19):6091-6. Epub 2011 Sep 20. Review.
Sonestedt E, Ericson U, Gullberg B, Skog K, Olsson H, Wirfält E. Do both heterocyclic amines and omega-6 polyunsaturated fatty acids contribute to the incidence of breast cancer in postmenopausal women of the Malmö diet and cancer cohort? Int J Cancer. 2008 Oct 1;123(7):1637-43.
Spencer L, Mann C, Metcalfe M, Webb M, Pollard C, Spencer D, Berry D, Steward W, Dennison A. The effect of omega-3 FAs on tumour angiogenesis and their therapeutic potential. Eur J Cancer. 2009 Aug;45(12):2077-86. Epub 2009 Jun 1. Review.
Thiébaut AC, Chajès V, Gerber M, Boutron-Ruault MC, Joulin V, Lenoir G, Berrino F, Riboli E, Bénichou J, Clavel-Chapelon F. Dietary intakes of omega-6 and omega-3 polyunsaturated fatty acids and the risk of breast cancer. Int J Cancer. 2009 Feb 15;124(4):924-31.
Wendel M, Heller AR. Anticancer actions of omega-3 fatty acids--current state and future perspectives. Anticancer Agents Med Chem. 2009 May;9(4):457-70. Review.