Advisory on omega-6 fats and heart health dismays expert observers and ignores inconvenient evidence and dire implications for overall health
by Craig Weatherby
Substantial evidence links America’s extreme “omega-imbalance” to major health risks, so it was surprising to see a recent statement from the American Heart Association (AHA).
By “omega-imbalance”, we mean a very low intake of omega-3 fatty acids (from dark leafy greens and seafood), and very high intake of omega-6 fatty acids (from vegetable oils, packaged/prepared foods, and grain-fattened meats and poultry).
A group of researchers working on behalf of the AHA concluded that America’s extreme omega-imbalance does not raise cardiovascular risks… as long as people eat enough omega-3s from fish or supplements (Harris WS et al. 2009).
- American Heart Association downplays dangers of the omega-6 fat overload typical of American diets.
- AHA statement ignores documented heart- and general-health risks associated with America’s extreme “omega-imbalance”.
- Respected researchers dissected the AHA analysis and found fatal flaws.
The AHA’s evidence- reviewers affirmed the value of omega-3s to protect against heart-related disease and death.
But they overlooked or downplayed evidence that eating too many omega-6s blunts the cardiovascular benefits of dietary omega-3s, and promotes known risk factors.
Researchers generally agree that ideally, people should consume no more than six omega-6 molecules for every omega-3 molecule they ingest.
And ideally, most say we should consume only two to three omega-6 molecules for every omega-3 molecule.
This is the approximate “omega ratio” humans have eaten since prehistoric times… and it’s the ratio still eaten by modern hunter-gatherers, who are remarkably free of the degenerative health conditions that plague Western industrial countries, such as diabetes and cardiovascular disease.
But in reality, most Americans ingest 20 to 40 omega-6 fat molecules for every omega-3 molecule... a radical shift that took place only over the past 150 years, along with immigration from farms to cities, and the rise of cheap, processed foods and vegetable oils.
We’ve reported many studies that link cancer, metabolic syndrome, and more to the average American’s “omega-imbalance.”
In historical and evolutionary terms, the average American diet is extremely high in omega-6 fats, and very low in omega-3s.
There’s ample evidence to indicate that this modern omega-imbalance has very real health consequences.
Evidence of harm
Highly respected research scientists like William E. Lands, Ph.D., and Joseph Hibbeln, M.D., point to a large body of evidence indicating myriad health dangers associated with omega-imbalanced diets eaten here and abroad.
Their work was the subject of our article, titled “Report Finds Americans Need More Omega-3s and Less Omega-6s,” and we’ve published several other reports on research into the impacts of American’s omega-imbalance:
To see even more reports on the impacts of omega-imbalanced diets, see the Omega-3 / Omega-6 Balance section of our news archive.
American Heart Association advisory misses the big picture
We can’t predict whether the AHA team’s conclusion - which is both supported and contradicted by substantial evidence - will be confirmed over the long run.
For now, it seems irresponsible to ignore or downplay credible evidence that either flatly contradicts their conclusion or points to long-term risks from Americans’ grossly omega-imbalanced diets … an historically unprecedented eating pattern that’s spreading worldwide very speedily.
We cannot dispute any of the evidence cited as supporting their conclusions regarding heart risks, of which we were well aware.
But they ignored inconvenient evidence that contradicts their conclusions regarding heart health … as well as compelling evidence that positions America’s omega-imbalanced diets as a major risk to overall health.
In other words, the AHA team suffered from tunnel vision.
They should have acknowledged the large, fast-growing body of evidence which indicates that America’s omega-imbalance raises the risks of cancer, depression, and cardiac-related conditions like arterial inflammation, metabolic syndrome, and diabetes.
What the AHA review said
The authors of the AHA advisory analyzed previous evidence reviews (meta-analyses), individual clinical trials, and more than two dozen epidemiological studies, which compared people’s diets to their heart health status.
Epidemiological studies of various kinds
—observational, cohort, case-control and others
—show that people who eat the most omega-6 fatty acids usually have the least heart disease.
Some (not all) other studies—that have compared blood levels of omega-6s in heart patients to the levels in healthy people—associate low levels of omega-6s with lower rates of heart disease.
And, in controlled trials where people were randomly assigned to eat diets containing either high levels or low levels of omega-6s, those assigned to the omega-6-rich diets often have less heart disease and fewer heart attacks.
The AHA team was not the first to assert the irrelevance of very high omega-6 intake. Brandeis University researchers said this in 2004:
“…the balance between dietary [omega3 and omega-6] fatty acids an important consideration influencing cardiovascular health… [but] the absolute mass of essential fatty acids consumed, rather than [the omega3/omega-6] ratio, should be the first consideration...” (Wijendran V, Hayes KC 2004).
There is little doubt that replacing the saturated fats in animal foods with polyunsaturated omega-6 fats in vegetable oils lowers the risk for heart disease, due partly to changes in blood cholesterol profiles.
But the AHA review compared a heart-unhealthier diet (high in fatty meats and dairy, low in plant-source foods and oils) to a heart-healthier diet (low in fatty meats and dairy, highs in plant-source foods and oils).
And they ignored evidence that an omega-balanced diet—with fewer omega-6s and more omega-3s than average in America—represents the ideal diet for heart and overall health.
Evidence that the omega-imbalance does matter
The AHA team made sweeping statements that ignored major evidence that undermines their conclusion.
For example, the AHA’s assertions ignored the findings of the famous Lyon Diet Heart study, which made “Mediterranean diet” a household word.
This large clinical trial involved two groups of heart patients from France who were fed one of two diets:
Mediterranean diet low in omega-6 polyunsaturated fats.
A “heart healthy” diet based on American Heart Association guidelines.
The group eating the Mediterranean diet had a striking 70 percent reduction in all causes of death, including cancer, compared to the group eating the AHA’s “heart healthy diet.”
The Lyon study was designed to be low in omega-6 fats, in order to mimic the indigenous Mediterranean diet of Aegean Islanders, who have very low rates of heart disease.
The AHA’s diet guidelines were designed to reduce saturated fats, but made no distinctions between the omega-6 and omega-3 polyunsaturated fats expected to take their place.
Because the American diet is very low in sources of omega-3s, and awash in omega-6 food sources, most people who follow AHA diet guidelines will end up overloading on omega-6s.
Just last month, Lyon Heart Study lead author Dr. Michel de Lorgeril criticized researchers who overlook the omega-6 factor in his Lyon Heart Study results, saying, “…the epidemiologists do not capture one major lipid [dietary fat] characteristic of the Mediterranean diet, which is [that it is] actually low in omega-6 [fats].”
And as bestselling fatty acid and weight control researcher Barry Sears, Ph.D. wrote in response to the AHA statement, “…none of the references in that article referred to the Lyon Diet Heart Study, which represented one of largest dietary intervention studies ever conducted. The failure to discuss this major study and its implications… in your Science Advisory greatly undermines its conclusion that the current consumption of omega-6 fatty acids is safe for the American public” (Sears B 2009).
In fact, there was enough scientific evidence 10 years ago to prompt fatty acid researcher Artemis Simopoulos, M.D. to recommend an upper limit for intake of omega-6 fats, to protect heart and overall health (Simopoulos AP et al. 1999; Simopoulos AP 2008).
In addition to epidemiological evidence, we have a great deal of lab evidence from animal and cell studies, showing that omega-imbalanced diets worsen proven risk factors for cardiovascular disease (Lai CQ et al 2006; Louheranta AM et al 1996; Dwyer JH et al 2004; Ghosh S et al. 2007; Ramsden CE et al 2009).
Leading researchers publish letter refuting AHA stance
We’d like to paraphrase key excerpts from a letter to the editor of the journal that published the AHA statement.
To those familiar with the literature, this letter from three leading fatty acid researchers constitutes a persuasive, pungent rebuttal of the AHA team’s broad generalizations.
We should note that instead of generic “omega-6s” the letter’s authors actually referred to intakes of the short-chain omega-6 fat in vegetable oils called LA, which blocks conversion of plant-source omega-3s to the essential long-chain omega-3s (EPA and DHA) found in human cells and in fish.
These were key points made by three expert critics of the AHA statement:
The AHA team excluded two studies that showed increased rates of adverse cardiovascular events and mortality in people place on omega-6-rich diets, and one that concluded that diets lower in omega-6s are more effective for prevention of coronary heart disease.
One study the AHA included had serious confounding factors, including greater long chain omega-3 intake in the group receiving extra omega-6s.
Lead author William S. Harris, Ph.D. overlooked the fact that higher intakes of omega-6 fats lower omega-3 blood levels, which he acknowledges elsewhere as a risk to heart health.
Evidence indicates that lower dietary intakes of omega-6s raise tissue levels of long chain omega-3s and lowers levels of omega-6s… changes that clearly benefit humans.
As they concluded, “The combined available data and flawed meta-analysis do not justify concluding that high omega-6 diets reduce coronary heart disease. On the contrary, careful consideration suggests that omega-6 reduction is likely a better strategy for coronary heart disease prevention.
“The widespread consumption of diets with more than 2% of calories from omega-6s should be recognized for what it is—a massive uncontrolled human experiment without adequate rationales or proven mechanisms.” (Ramsden CE et al. 2009)
British review highlights key flaw in AHA statement
Last year, British researchers interested in the omega-balance issue reviewed the results of a controlled clinical trial called OPTILIP, and of a “stable isotope” tracer study that followed the fate of dietary fats in the body.
The British review included this statement, which at first blush seems to support the AHA team’s conclusions:
“These two studies were independently unanimous in concluding that the ratio of omega-6/omega-3 polyunsaturated fatty acids is of no value in modifying cardiovascular disease risk.”
However, as they went on to say, the isotope tracer study confirmed a major point made by proponents of omega-balanced diets.
Namely, the relative amounts of plant-source omega-6s and plant-source omega-3s we eat affects the efficiency with which our bodies convert short-chain, plant-source omega-3s into long-chain omega-3s (EPA and DHA), which are the only kinds proven to enhance heart health.
In other words, the Brits were warning that omega-imbalanced diets yield too few omega-3s in our cell membranes to provide optimal protection from heart risks.
Accordingly, the UK team concluded that their review reinforces recommendations to increase omega-3 intakes and decrease intake of omega-6s.
de Lorgeril M et al. Mediterranean Diet, Traditional Risk Factors, and the Rate of Cardiovascular Complications After Myocardial Infarction : Final Report of the Lyon Diet Heart Study Circulation1999;99:779-785 (Free full text)
de Lorgeril M, Reanud S, Mamelle N, Salen P, Martin JL, Monjuad I, Gidolet J, Touboul P, Delaye J. Mediterranean alpha-linolenic acid-rich diet in secondary prevention of coronary heart disease. Lancet. 1994;343:1454-1459.
de Lorgeril M, Salen P, Martin JL, Monjaud I, Delaye J, Mamelle N. 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.
Dwyer JH et al. Arachidonate 5-Lipoxygenase Promoter Genotype, Dietary Arachidonic Acid, and Atherosclerosis. N Engl J Med 2004 350: 29-37.
Ghosh S, Novak EM, Innis SM. Cardiac proinflammatory pathways are altered with different dietary n-6 linoleic to n-3 -linolenic acid ratios in normal, fat-fed pigs. Am J Physiol Heart Circ Physiol (2007)293: H2919-H2927.
Griffin BA. How relevant is the ratio of dietary n-6 to n-3 polyunsaturated fatty acids to cardiovascular disease risk? Evidence from the OPTILIP study. Curr Opin Lipidol. 2008 Feb;19(1):57-62. Review.
Harris WS, Mozaffarian D, Rimm E, Kris-Etherton P, Rudel LL, Appel LJ, Engler MM, Engler MB, Sacks F. 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. 2009 Feb 17;119(6):902-7. Epub 2009 Jan 26.
Hibbeln JR et al. Healthy intakes of n-3 and n-6 fatty acids: estimations considering worldwide diversity.Am J Clin Nutr 2006 83: S1483-1493. Free Full Text.
Lai CQ et al. Dietary Intake of n-6 Fatty Acids Modulates Effect of Apolipoprotein A5 Gene on Plasma Fasting Triglycerides,Remnant Lipoprotein Concentrations, and Lipoprotein Particle Size: The Framingham Heart Study.Circulation (2006)113: 2062-2070.
Lands WE. Dietary fat and health: the evidence and the politics of prevention: careful use of dietary fats can improve life and prevent disease. Ann N Y Acad Sci. 2005 Dec;1055:179-92.
Leaf A. Dietary Prevention of Coronary Heart Disease: The Lyon Diet Heart Study.Circulation 1999;99:733-735.
Louheranta AM et al. Linoleic acid intake and susceptibility of very-low-density and lowdensity lipoproteins to oxidation in men. Am J Clin Nutr 1996 63: 698-703.
Okuyama H. Prevention of Coronary Heart Disease From the Cholesterol Hypothesis to omega-6/omega-3 Balance. World Review of Nutrition and Dietetics (2007) Vol. 96:1-158.
Ramsden CE, Hibbeln JR, Lands WE. Letter to the Editor re: Linoleic acid and coronary heart disease. Prostaglandins Leukot. Essent. Fatty Acids (2008), by W.S. Harris. Prostaglandins Leukot Essent Fatty Acids. 2009 Jan;80(1):77; author reply 77-8. Epub 2009 Jan 14.
Simopoulos AP. The importance of the omega-6/omega-3 fatty acid ratio in cardiovascular disease and other chronic diseases.Exp Biol Med (Maywood). 2008 Jun;233(6):674-88.
Simopoulos AP, Leaf A, Salem N. Workshop on the Essentiality of and Recommended Dietary Intakes for Omega-6 and Omega-3 Fatty Acids.J Am Coll Nutr 1999 18: 487-489.
Tribole E..What happened to do no harm? The issue of dietary omega-6 fatty acids.Prostaglandins Leukot Essent Fatty Acids. 2009 Jan 13. [Epub ahead of print] .
Wang J et al. 5-Lipoxygenase and 5-Lipoxygenase-Activating Protein Gene Polymorphisms, Dietary Linoleic Acid, and Risk for Breast Cancer. Cancer Epidemiol Biomarkers Prev October 1, 2008(17): 2748-2754
Wijendran V, Hayes KC. Dietary n-6 and n-3 fatty acid balance and cardiovascular health. Annu Rev Nutr. 2004;24:597-615. Review.