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“Healthy” vegetable oils may actually increase risk of heart disease, researchers say

November 11, 2013

Calling on Health Canada to reconsider health claim for omega‑6 oils on food labels

TORONTO, ON — Healthy eat­ing just got a lit­tle more com­pli­cat­ed.

New research from the Uni­ver­si­ty of Toron­to shows cer­tain veg­etable oils that claim to be healthy may actu­al­ly increase the risk of heart dis­ease.

And the results mean Health Cana­da should recon­sid­er cho­les­terol-low­er­ing claims on food labelling, says Dr.Richard Bazinet, lead author of the new study which is avail­able online now at the Cana­di­an Med­ical Asso­ci­a­tion Jour­nal.

“This is impor­tant infor­ma­tion for peo­ple buy­ing cer­tain foods because of the heart ben­e­fits when real­ly, that’s not accu­rate,” says Bazinet, of U of T’s depart­ment of nutri­tion­al sci­ences. “While most of these foods are a good choice, there are a few notable excep­tions.”

Bazinet and his team report that replac­ing sat­u­rat­ed ani­mal fats with polyun­sat­u­rat­ed veg­etable oils had become com­mon prac­tice for con­sumers, based on the under­stand­ing that such oils reduce serum cho­les­terol lev­els and help pre­vent heart dis­ease. Since 2012, Health Canada’s Food Direc­torate has allowed the food indus­try to use a label on the oils – and foods con­tain­ing the oils – claim­ing “a reduced risk of heart dis­ease by low­er­ing blood cho­les­terol lev­els.”

But researchers say it’s more com­pli­cat­ed than the label sug­gests – and the prob­lem lies in the ratio of two kinds of polyun­sat­u­rates fat­ty acids found in the oils.

“Care­ful eval­u­a­tion of recent evi­dence, how­ev­er, sug­gests that allow­ing a health claim for veg­etable oils rich in omega‑6 linole­ic acid but rel­a­tive­ly poor in omega‑3 α‑linolenic acid may not be war­rant­ed,” write Bazinet and Michael Chu, Law­son Health Research Insti­tute and Divi­sion of Car­diac Surgery at West­ern Uni­ver­si­ty in Lon­don, Ontario.

Corn and saf­flower oil, which are rich in omega‑6 linole­ic acid but con­tain almost no omega‑3 α‑linolenic acid, are not asso­ci­at­ed with ben­e­fi­cial effects on heart health, Bazinet says.

The authors cite a study pub­lished ear­li­er this year in Feb­ru­ary 2013 in which “…the inter­ven­tion group replaced sat­u­rat­ed fat with sources of saf­flower oil or saf­flower oil mar­garine (rich in omega‑6 linole­ic acid but low in omega‑3 α‑linoleic acid). They found that the inter­ven­tion group had serum cho­les­terol lev­els that were sig­nif­i­cant­ly decreased (by about 8%–13%) rel­a­tive to base­line and the con­trol group, which is con­sis­tent with the health claim.”

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

“When the new results were added to a meta-analy­sis, the net result was a bor­der­line 33 per cent 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,” Bazinet says.

In Cana­da, omega‑6 linole­ic acid is found in corn and saf­flower oils as well as foods such as may­on­naise, creamy dress­ings, mar­garine, chips and nuts. Canola and soy­bean oils, which con­tain both linole­ic and α‑linolenic acids, are the most com­mon forms of oil in the Cana­di­an diet.

“We sug­gest that the health claim be mod­i­fied such that foods rich in omega‑6 linole­ic acid but poor in omega‑3 α‑linolenic acid be exclud­ed,” con­clude the authors.

(Read the research arti­cle in CMAJ.)


For more infor­ma­tion, please con­tact:

Michael Kennedy
Media Rela­tions Offi­cer
Tel: 416–946-5025

Media Rela­tions
Uni­ver­si­ty of Toron­to
Tel: 416–978-0100