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Are Vegetable Oils Heart Healthy?
Canadian doctors critique heart health claims for corn oil and other omega-6-rich types
11/18/2013By Craig Weatherby
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Image Put the corn oil back on the shelf. And don’t pick up canola or soy oil in its place.

Why? A new study supports fast-growing evidence that most vegetable oils don’t aid heart health ... and may harm it when consumed to excess.

Unfortunately, the authors focused entirely on the three oils highest in omega-6 fatty acids – corn, safflower, and sunflower.

As a result, their study downplays a bigger health disaster … the gross excess of omega-6 fatty acids in the average American’s diet, which stems from a wider variety of vegetable oils

For more on this topic, see “America’s Sickening ‘Omega Imbalance’” and the Omega-3 / Omega-6 Balance section of our news archive.

That excess can be traced to the abundance of omega-6 fats in all of the commonly used vegetable oils: corn, sunflower, cottonseed, safflower, canola, peanut, sesame, and soy.

The exceptions to this list are “hi-oleic” sunflower and safflower oils, which come from plants bred to produce little omega-6 fat, but lots of the same monounsaturated fat found in olive oil (oleic acid).

Monounsaturated fat is clearly safe for heart health, and predominates in olive oil, macadamia nut oil, and hi-oleic” sunflower and safflower oils.

And extra virgin grade olive oil is uniquely rich in rare, tyrosol-type antioxidants proven to provide strong cardiovascular benefits.

An unhealthy imbalance
The available evidence indicates that people thrive best – and reduce their risk of most major diseases – on diets providing about three parts omega-6 fats to one part omega-3 fats.

But Americans’ relative intakes of omega-6s to omega-3s shifted dramatically in favor of omega-6 fats over the past 100 years … a trend that accelerated sharply in the late 1960’s.

The intake ratio now stands at about 20 parts omega-6 fats to one part omega-3. As prominent fatty acid researchers wrote almost a decade ago, “The increases in world [omega-6] LA consumption over the past century may be considered a very large uncontrolled experiment that may have contributed to increased societal burdens of aggression, depression, and cardiovascular mortality” (Hibbeln JR et al 2004).

American’s sharp shift from saturated animal fats (e.g., butter and lard) to omega-6-rich vegetable oils began more than 40 years ago, when health authorities began to assert – wrongly – that dietary saturated fat and cholesterol promote heart disease.

A British cardiologist’s recent, high-profile rebuttal of the claim that dietary saturated fat and cholesterol drive heart disease drew wide praise for its authors’ courage in defying conventional wisdom … see “Heart-Diet Myths Get a Busting”. 

New study contradicts conventional wisdom on fats
Findings reported by Canadian researchers show that common vegetable oils – instead of being heart-healthy as claimed for decades – raise the risk of heart disease.

And the authors say their results mean that Health Canada – that country’s counterpart to the U.S. FDA – should reconsider cholesterol-lowering claims on food labeling.

Since 2012, Health Canada’s Food Directorate has allowed food labels to say that polyunsaturated vegetable oils – and foods containing them – offer “a reduced risk of heart disease by lowering blood cholesterol levels.”

But the Canadian scientists conclude that it’s more complicated than the approved label-claim language suggests – with the problem lying in the ratio of omega-3 and omega-6 polyunsaturated fatty acids in the oils.

As they wrote, “Careful evaluation of recent evidence suggests that allowing a health claim for vegetable oils rich in omega-6 linoleic acid but relatively poor in omega-3 ALA (alpha-linolenic acid) may not be warranted.” (Bazinet RP, Chu MW 2013)

Corn and safflower oils, which are rich in omega-6 LA (linoleic acid) – but contain almost no omega-3 ALA (alpha-linolenic acid) – are not associated with heart health benefits, Bazinet says.

The authors cite a U.S.-Australian study published in February of 2013 in which one group replaced saturated fat with safflower oil or safflower oil margarine, which are rich in omega-6 LA but low in omega-3 ALA.

(We covered this landmark research at the time … see “Heart Risks Raised by Omega-6 Excess”.)

As expected, cholesterol levels dropped by eight to 13 percent in the safflower oil group, compared with the control group.

However, rates of death from all causes of cardiovascular disease and coronary artery disease significantly increased in the treatment group.

Dr. Bazinet detailed the lack of benefit in the safflower oil group:
“When the new results were added to a meta-analysis [evidence review], the net result was a borderline 33 percent increase in heart disease risk for oils rich in omega-6 and poor in omega-3, with absolutely no evidence of a benefit as is implied by the health claim.”

“We suggest that the health claim be modified such that foods rich in omega-6 LA but poor in omega-3 ALA be excluded [from the claim],” conclude the authors.

They also suggest that these oils be replace with canola and soybean oils, which contain both omega-6 LA and omega-3 ALA.

However, scientists familiar with the bigger problem – such as the authors of the study we covered in “Heart Risks Raised by Omega-6 Excess” – beg to differ.

Because the average American’s diet is awash in a historically unprecedented flood of omega-6 fats, he or she should minimize intake of any of the oils in which omega-6 LA predominates – including canola and soybean oils – and foods made with them.


Sources
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  • Bazinet RP and Chu MWA. Omega-6 polyunsaturated fatty acids: Is a broad cholesterol-lowering health claim appropriate? CMAJ 2013; DOI: 10.1503/cmaj.130253.
  • Blasbalg TL, Hibbeln JR, Ramsden CE, Majchrzak SF, Rawlings RR. Changes in consumption of omega-3 and omega-6 fatty acids in the United States during the 20th century. Am J Clin Nutr. 2011 May;93(5):950-62. doi: 10.3945/ajcn.110.006643. Epub 2011 Mar 2. Br J Nutr. 2010 Dec;104(11):1586-600. doi: 10.1017/S0007114510004010.
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  • University of Toronto (UT). “Healthy” vegetable oils may actually increase risk of heart disease, researchers say. November 11, 2013. Accessed http://media.utoronto.ca/media-releases/health-medicine/healthy-vegetable-oils-may-actually-increase-risk-of-heart-disease-researchers-say/
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