Objective. To evaluate the effectiveness of replacing dietary saturated fat with omega 6 linoleic acid, for the secondary prevention of coronary heart disease and death.
Design. Evaluation of recovered data from the Sydney Diet Heart Study, a single blinded, parallel group, randomized controlled trial conducted in 1966-73; and an updated meta-analysis including these previously missing data.
Setting. Ambulatory, coronary care clinic in Sydney, Australia.
Participants. 458 men aged 30-59 years with a recent coronary event.
Interventions. Replacement of dietary saturated fats (from animal fats, common margarines, and shortenings) with omega 6 linoleic acid (from safflower oil and safflower oil polyunsaturated margarine). Controls received no specific dietary instruction or study foods. All non-dietary aspects were designed to be equivalent in both groups.
Outcome measures. All cause mortality (primary outcome), cardiovascular mortality, and mortality from coronary heart disease (secondary outcomes). We used an intention to treat, survival analysis approach to compare mortality outcomes by group.
Results. The intervention group (n=221) had higher rates of death than controls (n=237) (all cause 17.6% v 11.8%, hazard ratio 1.62 (95% confidence interval 1.00 to 2.64), P=0.05; cardiovascular disease 17.2% v 11.0%, 1.70 (1.03 to 2.80), P=0.04; coronary heart disease 16.3% v 10.1%, 1.74 (1.04 to 2.92), P=0.04). Inclusion of these recovered data in an updated meta-analysis of linoleic acid intervention trials showed non-significant trends toward increased risks of death from coronary heart disease (hazard ratio 1.33 (0.99 to 1.79); P=0.06) and cardiovascular disease (1.27 (0.98 to 1.65); P=0.07).
Conclusions. Advice to substitute polyunsaturated fats for saturated fats is a key component of worldwide dietary guidelines for coronary heart disease risk reduction. However, clinical benefits of the most abundant polyunsaturated fatty acid, omega 6 linoleic acid, have not been established. In this cohort, substituting dietary linoleic acid in place of saturated fats increased the rates of death from all causes, coronary heart disease, and cardiovascular disease. An updated meta-analysis of linoleic acid intervention trials showed no evidence of cardiovascular benefit. These findings could have important implications for worldwide dietary advice to substitute omega 6 linoleic acid, or polyunsaturated fats in general, for saturated fats.
asked byThe_Quilt (25482)
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on June 05, 2013
at 09:18 PM
You really should have put a quote up. Since there is no quote I don't want to waste my time creating a free account only to find that Chris Ramsden has just interviewed you or something. Don't get me wrong, I read your stuff, but too often I feel like I've been rickrolled when I click on a link that you give here.
on June 06, 2013
at 07:31 PM
I like this study. An NIH researcher establishes that linoleic acid increases heart disease deaths? Fantastic. I think Dr. Harris would be pretty happy too.
I know the Quilt has had run-ins here before and, yes, this is not news to us. But wouldn't it be nice if the mainstream started to wake up to the idea that canola oil ain't so heart-healthy after all?
Kudos Jack! Although I'm not sure why you still post here. Seems like PaleoHacks has jumped the shark.
(I took a chance and didn't get rick-rolled...)