Health Canada should rescind the permission it granted to manufacturers of some cooking oils to put health claims on their product labels, a new analysis published Monday in the Canadian Medical Association Journal argues.
The article, written by a nutritional science researcher and a cardiologist, says the available evidence suggests oils rich in omega-6 polyunsaturated fatty acids but containing little or no omega-3 fatty acids are not protective of heart health and may even slightly increase the risk of heart disease.
"I can't follow the logic of giving these ones a health claim," said Richard Bazinet of the University of Toronto's department of nutritional sciences.
"When you look at evidence – beneficial, neutral, bad – we're debating bad or neutral. … We're nowhere near the beneficial side of the argument, which is what a health claim should require."
The products Bazinet is referring to are corn, sunflower and safflower oils, which are rich in omega-6 fatty acids, but contain negligible amounts of omega-3 fatty acids.
He and co-author Dr. Michael Chu analyzed the findings of existing studies; they did not conduct new research on these oils.
They noted that while there is evidence supporting the claim that cooking oils containing a mix of omega-6 and omega-3 fatty acids lower the risk of heart disease, the same is not true for omega-6 on its own.
And further, there are hints in the data that omega-6-rich oils may be associated with a slightly elevated risk of heart disease.
"It's not like we're debating whether this protected people or had no effect. We're saying the debate is: Would it be harmful in the general population or not?" Bazinet said.
Oils that contain a mix of omega-3 and omega-6 fatty acids are canola and soybean, which are in fact the oils Canadians consume most frequently. Canola oil and soybean oil comprise about 55 per cent and 25 per cent, respectively, of Canadian oil intake.
By contrast, cooking oils rich in omega-6 polyunsaturated fatty acids make up only about 5 per cent of Canadian consumption.
Olive oil is a monounsaturated product and was not included in their analysis of studies, said Bazinet, adding that it is considered a healthy dietary choice.
"We're not telling people they have to go out and lower their intakes of this, because they're not very high," he said of oils rich in omega-6. "What we're just saying is: If we're going to take these health claims seriously, these products shouldn't be allowed one."
Stephen Cunnane, a professor whose research focuses on brain metabolism and aging at the University of Sherbrooke, concurred with Bazinet's and Chu's assessment.
"I would agree that there's not good evidence that the omega-6 oils alone are beneficial," Cunnane said.
In 2012, Health Canada agreed to let manufacturers of cooking oils containing either omega-6 or a combination of omega-6 and omega-3 fatty acids claim on their product labels that these oils help reduce the risk of heart disease by lowering cholesterol.
Health Canada did not immediately reply to questions about whether it would reconsider its position on omega-6-rich cooking oils.