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

BMJ 2006; 332 doi: http://dx.doi.org/10.1136/bmj.38755.366331.2F (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
for
mortality, cardiovascular disease and cancer, without considering the
impact
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
fats
because they compete for the same rate-limiting enzymes. A high
proportion
of omega-6 to omega-3 fat in the diet shifts the physiological state of
the
body toward the pathogenesis of many diseases: prothrombotic,
proinflammatory and proconstrictive (1).

Chronic excessive production of omega-6 eicosanoids is associated
with
heart attacks, thrombotic stroke, arrhythmia, arthritis, osteoporosis,
inflammation and cancer. Furthermore, coronary heart disease mortality
has
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
about
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
Diet
Heart study illustrated the significant impact of a Mediterranean diet,
with a
striking reduction in all-cause mortality and coronary heart disease; this
diet
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
saturated
fats). Consequently, they now have one of the highest omega-6 fat intakes
in
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
health
picture. Omega-3 fats provide little if any benefit if there are
excessive
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
scientific
community has published guidelines addressing the need to balance omega
-6 and omega-3 fats, by decreasing the former while increasing the latter
(7).

1. Simopoulus, AP and Cleland LG. Omega-6/Omega-3 Essential Fatty
acid
ratio: the scientific evidence. World Review of Nutrition and Dietetics.
(2003):
92:1-174.

2. Lands EM. Dietary fat and health: the evidence and the politics
of
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

(2005).81:341-354.

De Lorgeril et al. Mediterranean diet, traditional risk factors, and
the rate of
cardiovascular complications after myocardial infarction; final report of
the
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
syndrome
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
essentiality
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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