"First, an increased linoleic acid content of LDL increases its sensitvity to oxidation, and it is the oxidised LDL that is involved in atherosclerotic plaque growth. (linoleic acid is the unsaturated omega-6s found in oils, nuts, & seeds)
Hence, an increase in linoleic acid intake could actually promote plaque growth and cardiovascular disease.
Second, there was some evidence that linoleic acid could promote certain cancers, especially in animal models. These doubts were captured in an additional, often ignored, recommendation related to PUFA (the omega-6 polyunsaturated fatty acids) in the UK: "there is reason to be cautious about high intakes of n-6 PUFAs, and we recommend that the proportion of the population consuming in excess of about 10% of energy (the calories in omega-6 oils or nuts) should not increase."
The AHA advisory dismissed concerns about inflammation, thrombosis, and LDL oxidation."
-Philip C. Calder, "Commentary: The American Heart Association Advisory on n-6 fatty acids: evidence-based or biased evidence?" Br J Nutr 104:1575-76, Dec. 2010-
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This morning I received an email from Evelyn Tribole, MS, RD asking for my help. Tribole is an award-winning dietitian who is at the forefront of research about the omega-6 connection to health & disease.
She was anxious to get the word out about a just-published major review of medical research that refutes the recent American Heart Association's "Eat Your Omega-6 Fats" advisory. Turns out the research on which the advisory was based was questionable, flawed, incorrect, and can do harm.
Three NIH scientists, Christopher Ramsden, Joseph Hibbeln, & Sharon Majchrzak, all experts in omega-6s & omega-3s, are the authors of this just published major paper in the well-respected British Journal of Nutrtition. For some unknown reason these NIH scientists were unable to get their responses to the AHA "omega-6 advisory" published in Circulation. Hmm. I wonder why.
Tribole was experiencing some "technical difficulties" with her website and her post about this new research wasn't going to appear until Monday. That's where I come in. I said I'd be glad to publish her post that will eventually appear on her blog, "Omega-6 Fat News and Commentary", but first I had to give you all some background to this controversial story.
The Strange Story of the American Heart Association's Advisory to "Eat Your Omega-6 Fats"
The American Heart Association thinks we are worrying way too much about omega-6s and inflammation. They're afraid that if we don't consume enough polyunsaturated fats (think mayonnaise, safflower, cottonseed, corn, soybean, unnamed vegetable & sunflower oils) we'll do ourselves harm and actually cause heart disease. So...last year they issued an urgent advisory in Circulation 119:902-907, "Omega-6 fatty acids and risk for cardiovascular disease: a science advisory from the American Heart Association".
Johns Hopkins' Heart Health issued their own "Health Alert" on November 12, 2010, based on this flawed advisory published in Circulation, "Heart Health Advice: Don't Skimp on Your Omega-6 Fatty Acids".
"Over the past few years, you may have heard the advice to boost you intake of omega-3 fatty acids and to cut down on omega-6 fats. Now a science advisory from the American Heart Associaiton (AHA) urges people to continue to eat their omega-6s. According to the advisory, omega-6 fatty acids should account for at least 5-10% of your daily calories. In addition, cutting back on omega-6s is more likely to contribute to heart disease than to combat it, says the AHA."
Too put it bluntly, this is craziness! No one in the U.S. is omega-6 deficient. It's just not possible. Omega-6s are in every food we eat, like corn, oats, soy, brown rice, garbanzo beans, and nuts--even foods high in omega-3s, like chia seed & flax have omega-6s. You wouldn't need even a teaspoon of added oil to get enough omega-6s into your diet to fulfill the 5-10% of your daily calorie requirement--yet the AHA advisory appears to give us all license to down even more oils than we already do.
When I first read the article in Circulation, I just scratched my head. What are they talking about? Sure, we need enough omega-6s for health, but getting enough has never been a problem. Are they just trying to justify their 1980's recommendation to cut out saturated and trans fat and substitute them with polyunsaturated oil? Take a look at how well that recommendation played out in Israel, a country that really took the advice to up their intake of oil "to heart".
"There is also something known as the Israeli Paradox--an increase in CHD founded on an increase in PUFA. Israelis ditched the saturated fat, and as a country embraced the polyunsaturated oils, as a health strategy. Their incidence & mortality from heart disease rose as their intake of linoleic acid (high omega-6s) increased--they now eat more than any country in the world (more than 30 grams a day).
Even though they eat less animal fat & cholesterol & fewer calories than Americans, they have comparable rates of heart disease, obesity, diabetes, & many cancers. "They have an ideal diet, as far as the American food pyramid is concerned, but far from ideal health. Israeli Jews may be regarded as a population-based dietary experiment of the effect of a high omega-6 polyunsaturated fatty acid diet" It's called the Israeli paradox, & until recently, this diet was widely recommended." Susan Alport, "Queen of Fats.
Click on the graph to enlarge it.
For more info on omega-6s read: My Amateur Spin on Putting the Diet Puzzle Pieces Together - the Omega-6 and Omega-3 Face-Off in Health and Disease.
Evelyn Tribole's summary of research that refutes the AHA's "Eat Your Omega-6 Fat" Advisory
Meta-analysis Reveals “Heart Healthy Omega-6 Fat” Ups Risk of Heart Disease
Bottom Line: The research upon which the American Heart Association based their "eat-your-omega-6-fat" advisory, is fatally flawed, according to the results of a meta-analysis study, which showed that a steady diet of omega-6 polyunsaturated fatty acids increases the risk of heart disease and death, especially for women . British J Nutr. Dec 2010.
Background: ln 2009 the American Heart Association (AHA) published a health advisory touting the benefits of eating a high omega-6 polyunsaturated fatty acids (PUFA), and warned that eating less than 5% of calories from omega-6 PUFA would be hazardous to heart health. [2-3].
The conclusion of AHA's advisory were seriously questioned in part, because of their failure to:
- Distinguish the types of PUFA used in studies, which also substantially increased omega-3 fats, which are a PUFAs.
- Include relevant trials with unfavorable results.
- Exclude poorly designed studies.
Notably, these studies did not provide or differentiate the specific fatty acid content of the intervention diets. (Yet the AHA recommended to specifically increase omega-6 PUFA).
These flaws prompted a team of National Institutes of Health (NIH) scientists to re-evaluate the data, using techniques resembling a scholarly forensic investigation.
Design: Nine randomized controlled trials (the gold standard of study design), were identifed, which met the criteria of having an intervention diet high in PUFA at the expense of other fat and also reported clinical outcome data.
Next came the detective work, worthy of an Agatha Cristy who-done-it. Most of the studies did not provide omega-3 fat data--it was just lumped together in the PUFA category. In order to track down the missing fatty acid data, (many of these studies were conducted over 40 years ago), they had to dig through newspaper archives, public records, scienti?c proceedings from national conferences and correspond with the study investigators (or their colleagues, if deceased).
Once the fatty acid data was collected, they were segregated into two categories:
- Mixed Diet (containing both omega-6 and omega-3 polyunsaturated fatty acids.)
- Omega-6 Specific Diet
Then the data was pooled to evaluate the the effect of the Omega-6 Specific Diet, compared to the effect of the Mixed Diet, on clinical outcomes. They also evaluated the potential confounding role of trans fatty acids.
Results: Here's what they found when evaluating the composition of the intervention diets.
- Only three of the nine so-called PUFA studies were "pure" omega-6 intervention trials, which upped omega-6, without a concurrent rise in dietary omega-3. Combined, these three studies had 9,500 participants.
- Four of the studies increased both the omega-3 PUFA (EPA and DHA) and omega-6 PUFA, which totaled over 1,700 participants. Notably, the researchers discovered that the Oslo Diet-Heart Study provided about 5 grams of EPA and DHA per day to the intervention group. (That's equivalent to about 16 fish oil capsules).
- The control diets had a mean estimated trans fatty acid content of 3% (a significant confounding factor, which unquestionably increases risk of heart disease).
Heart Disease and Death Outcomes
When the effects of the Omega-6 Specific Diet were compared to the Mixed Omega 6/omega-3 PUFA, the following health outcomes were discovered:
Omega-6 Specific Diet:
- Increased risk of heart disease and death, compared to the Mixed Diet intervention studies.
- The relative risk of cardiac death increased by 28%.
- Increased the risks of all relevant cardiovascular outcomes.
- There was only one study with women, which showed significant harm.
The Mixed Omega-6/Omega-3 Diet:
- There was 8% risk reduction of death from all causes.
- There was 22% risk reduction from heart disease death.
Conclusion: The scientists concluded, that not only is there no indication of health benefit, from increasing dietary omega-6 PUFA, but a possibility of harm. Therefore, they recommended that the public health advice to maintain or increase dietary omega-6 PUFA, should be reconsidered.
Study Quote:"The increased cardiovascular heart disease risks from omega-6 specific PUFA diets in our meta-analysis may be underestimated as omega-6 PUFA also replaced substantial quantities of trans fatty acids." An accompanying editorial applauded the “extensive detective work” by the NIH research team, led by Christopher Ramsden 
Commentary: There is more to this story. In my next post, I'll describe what went on behind the scenes, as three NIH scientists from this study, tried to get letters to the editor published in the AHA's scientific journal, Circulation, in response to their omega-6 advisory. (I was actually a participant and witness).
Links to Sources
 Christopher E. Ramsden,Joseph R. Hibbeln,Sharon F. Majchrzak and John M. Davis (2010).Omega-6 Fatty acid-specific and mixed polyunsaturate dietary interventions have different effects on CHD risk: a meta-analysis of randomised controlled trials. British Journal Nutrition. Dec 2010; 104(11): pp 1586-1600. [Preview]
 Harris WS et al. Omega-6 Fatty Acids and Risk for Cardiovascular Disease. A Science Advisory From the American Heart Association Nutrition Subcommittee of the Council on Nutrition, Physical Activity, and Metabolism; Council on Cardiovascular Nursing; and Council on Epidemiology and Prevention. Circulation published January 26, 2009. [Free Full Text.]
 American Heart Asssociation News Release. Omega-6 fatty acids: Make them a part of heart-healthy eating DALLAS, Jan. 27, 2009. [Free full Text]
 Philip C. Calder (2010).The American Heart Association advisory on n-6 fatty acids: evidence based or biased evidence? British Journal Nutrition. Dec 2010; 104(11): pp 1575-1576.[Abstact]
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Copyright © 2010 by Evelyn Tribole, MS, RD Published at http://www.EvelynTribole.com
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DISCLAIMER: The information is intended to inform readers and is not intended to replace specific advice from a health care professional. Copyright 2010 Evelyn Tribole, MS, RD