Omega-6 PUFAs and risk of cardiovascular disease

Jan 30, 2009

A new Science Advisory report from the American Heart Association recommends that omega-6 polyunsaturated fatty acids (PUFAs), as found in vegetable oils, nuts and seeds, are beneficial when part of a heart-healthy eating plan. Consumers should aim for at least 5-10% of energy (calories) from omega-6 PUFAs, and will derive most benefit when omega-6 PUFAs replace saturated or trans fats in the diet. Precise recommended daily servings will depend on physical activity level, age and gender, but range between 12 and 22 grams per day.

The AHA report also addresses the recent controversy that omega-6 fatty acids, via linoleic acid, which accounts for 85-90% of dietary omega-6, may actually increase inflammation and thereby increase rather than reduce cardiovascular risk. Any link between omega-6 and inflammation, says the AHA, comes from the fact that arachidonic acid, which can be formed from linoleic acid, is involved in the early stages of inflammation, but anti-inflammatory molecules are also formed; these suppress the production of adhesion molecules, chemokines and interleukins, all of which are key mediators of the atherosclerotic process. Thus, concludes the report, it is incorrect to view the omega-6 fatty acids as pro-inflammatory.

The report also reviewed epidemiological data and found that, in randomised controlled trials, those assigned to the higher omega-6 diets had less heart disease. A meta-analysis of several trials indicated that replacing saturated fats with PUFA lowered risk for heart disease events by 24%. Reducing omega-6 intakes, said the report, would be more likely to increase than to decrease the risk of CHD.

Professor Heinz Drexel from the VIVIT Research Institute at Feldkirch, Austria, speaking on behalf of the European Society of Cardiology, adds that the report not only recommends the consumption of at least 5-10% of energy from omega-6 PUFAs but indicates that intakes higher than 10% of energy appear safe and may even be even beneficial. This latter statement, says Professor Drexel, “is somewhat discordant with earlier recommendations made by other authorities”.

Commenting on the report, Professor Drexel adds: “This advisory is a resurrection of older recommendations on omega-6 PUFAs, in particular on linoleic acid. It is based on new ecological, case-control, prospective cohort and randomised controlled studies. Concerns raised in the past decade that omega-6 PUFAs may be pro-inflammatory are dispelled with evidence that omega-6 PUFAs have anti-inflammatory properties at the level of vascular endothelial cells. On balance, the advantages outweigh the disadvantages.

“However, the effects of Omega-6 PUFAs appear weak and require long-term interventions. Many studies in the past were not long enough for a nutritional intervention. Moreover, in the intervention studies other nutrients were changed along with the enrichment of omega-6 PUFAs.”

Reference: Harris WS, Mozaffarian D, Rimm E, et al. Omega-6 fatty acids and risk for cardiovascular disease. Circulation 2009; DOI: 10.1161/CIRCULATIONAHA.108.191627.

Provided by European Society of Cardiology

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deatopmg
1 / 5 (1) Jan 30, 2009
This study was conducted by the AHA. The same organization from whom one can purchase an endorsement for a product being heart healthy, whether it is or not.
This is the same self serving misinformation (except for the trans fat recommendation, that they have been forced into by the media) that has been promoted by the AHA and the American seed oil producers for greater than 5 decades. All in spite of the overwhelming evidence that omega-6 fatty acids are pro-inflammatory, contra AHA's conditional statements, when consumed at more than 5-10% of energy input. Omega-3 fatty acids are the ones converted to truely anti-inflammatory products.

To promote american seed oil sales, and possibly other agendas, the AHA continues to promulgate the myth that saturated fats cause heart disease when in fact evidence points to them being neutral to slightly beneficial in CVD (especially the medium chain length, C12/C14, ones). Note that saturated fatty acids are the only ones that the body produces from excess carbohydrates. What is the evolutionary benefit of that?
etribole
5 / 5 (1) Jan 31, 2009
Controversy and debate are an expected (and welcome) part of the scientific process. But the American Heart Association%u2019s recent advisory urging Americans to gobble up their omega-6 fat is an unconscionable disservice, to both the scientific process and the public health.

AHA made sweeping statements that are not supported by the research, while ignoring landmark studies, which don%u2019t support their views.

Do Countries with Low Omega-6 Fat Diets Have Higher Rates of Heart Disease?

Given the American Heart Association's rationale, we should see elevated heart disease in countries that eat diets low in omega-6 polyunsaturated fats. No, think Mediterranean diet. Cultures that eat Mediterranean diets have lower rates of heart disease.

Enter the Lyon Diet Heart study, a large intervention trial in which heart patients, were fed either a Mediterranean diet (low in omega-6 polyunsaturated fat) or a diet advocated by the American Heart Association, with indiscriminate use of polyunsaturated fats. The people eating the Mediterranean diet had a striking 70% reduction in all causes of death, including cancer, compared to the folks eating the "heart healthy diet".

Just last month, the lead Lyon Diet Heart scientist, de Legoril, chastised researchers for ignoring the omega-6 factor, "...the epidemiologists does not capture one major lipid characteristic of the Mediterranean diet, which is actually low in omega-6".

In 1999, there was enough scientific evidence to prompt scientists to recommend an upper limit for omega-6 fats, to no more than 6.7 grams per day [Simopoulos]. This ceiling is based on eating a maximum of 3% fat calories from omega-6 fat on a 2000 calorie diet. (Note, this is a similar level to the the Lyon Diet Heart study.) Now the American Heart Association is advocating double that amount.

A heart scientist is not expected to be an expert on cancer, and one would hope that when they claim there is no harm from eating the current high levels of omega-6 fat, that they would use an inter-disciplinary approach to confirm their thinking. Sadly, that's not what happened.

Large studies from the USA, France and Sweden indicate a compelling link between high intakes of omega-6 fat and breast cancer [Tribole.] For example, in a case-control study on nearly 1700 women, researchers demonstrated that women with a genotype in%uFB02uencing the LOX enzyme, had a two-fold increase in breast cancer risk if they ate high levels of the omega-6 fat, linoleic acid, and amount of 17.4g/day [Wang]. Yet, this genotype had no in%uFB02uence on breast cancer risk, if these women ate a lower linoleic acid diet.

Lastly, there is a curious association with Unilever, a large global margarine manufacturer. Three of the 12 scientists declared that they received either advisory or consulting fees from this food conglomerate. Keep in mind that margarines, salad dresings and spreads are among the highest sources of omega-6 fat in westernized countries.

For links to the full text studies see:
http://omega-6-om...lth.aspx