Risks and benefits of omega 3 fats for mortality, cardiovascular disease, and cancer: systematic review

BMJ 2006; 332 doi: (Published 30 March 2006) Cite this as: BMJ 2006;332:752

Excess Omega-6 Fats Thwart Health Benefits from Omega-3 Fats

Conducting a meta-analysis study on the effectiveness of omega-3 fats
mortality, cardiovascular disease and cancer, without considering the
of excess omega-6 fat in the diet, is akin to reviewing the efficacy of a
healthy diet without factoring the effects of smoking.

Excess omega-6 fats interfere with the health benefits of omega-3
because they compete for the same rate-limiting enzymes. A high
of omega-6 to omega-3 fat in the diet shifts the physiological state of
body toward the pathogenesis of many diseases: prothrombotic,
proinflammatory and proconstrictive (1).

Chronic excessive production of omega-6 eicosanoids is associated
heart attacks, thrombotic stroke, arrhythmia, arthritis, osteoporosis,
inflammation and cancer. Furthermore, coronary heart disease mortality
been demonstrated to be proportional to plasma levels of long chain omega
-6 fat. (2)

Prior to industrialization, no population has been exposed to the
current high
levels of omega-6 polyunsaturated fats in westernized diets. Today we eat

fat that did not exist 100 years ago, such as cottonseed oil (3). Humans
evolved on a diet with a balanced ratio of omega-6 to omega-3 fats of
1:1. Today, that ratio in westernized countries is near 17:1.

The Greenland Inuit Eskimos are famous for their high omega-3 fat
diet, but
just as importantly, their diet was also low in omega-6 fat. The Lyon
Heart study illustrated the significant impact of a Mediterranean diet,
with a
striking reduction in all-cause mortality and coronary heart disease; this
was low in omega-6 fat (4).

Cultures that suddenly increase their omega-6 fat intake experience
markedly higher mortality rates and health problems. When Okinawans
tripled their omega-6 fat intake, they experienced a rise in cancer and
cardiovascular disease, which Japanese researchers called “excess linoleic

acid syndrome” (5). Notably, this syndrome occurred in the presence of
consuming fatty fish.

Israel embraced a high polyunsaturated fat diet (at the expense of
fats). Consequently, they now have one of the highest omega-6 fat intakes
the world, along with an unexpected high incidence of chronic western
diseases, which researchers term the “Israeli paradox” (6).

Eating an adequate amount of long chain omega-3 fats, whether through

regular fish consumption or fish oil supplements is only half of the
picture. Omega-3 fats provide little if any benefit if there are
dietary omega-6 fats. It’s puzzling that the authors did not address this

issue as a limitation of their study, especially when the international
community has published guidelines addressing the need to balance omega
-6 and omega-3 fats, by decreasing the former while increasing the latter

1. Simopoulus, AP and Cleland LG. Omega-6/Omega-3 Essential Fatty
ratio: the scientific evidence. World Review of Nutrition and Dietetics.

2. Lands EM. Dietary fat and health: the evidence and the politics
prevention. Annal New York Academy of Sciences (2005). 1055:179-192.

3.Cordain, L et al. Origins and evolution of the Western diet: health

implications for the 21st century. American Journal of Clinical Nutrition


De Lorgeril et al. Mediterranean diet, traditional risk factors, and
the rate of
cardiovascular complications after myocardial infarction; final report of
Lyon Diet Heart Study. Circulation (1999)99;779-785.

Okuyama, H et al. Dietary fatty acids—the n-6/n-3 balance and chronic

elderly diseases: excess linoleic acic and relative n-3 deficiency
seen in Japan. Prog. Lipid. Res (1997); 35(4):409-457.

Dubnov G. and Berry EM. Omega-6/omega-3 fatty acid ratio: The Israeli

Paradox. World Review of Nutrition and Dietetics. (2003):92:81-91.

Simopoulos AP, Leaf A, Salem Jr N. Workshop statement on the
of and recommended dietary intakes for omega-6 and omega-3 fatty acids.
Prostaglandins, Leukot Essential Fatty Acids (2000) 63:119-121.

Competing interests:
None declared

Competing interests: No competing interests

27 March 2006
Evelyn f Tribole
Consulting Nutritionist
15615 Alton Pkwy, Suite 450, Irvine, CA 92618 USA
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