Reanalysis Suggests Omega-6-Rich Diet of No Benefit to CHD Risk

Swapping saturated fat for omega-6 fatty acids does not improve clinical outcomes or decrease mortality risk from coronary heart disease or all causes, according to a recent analysis.

Findings from the Minnesota Coronary Experiment, a double-blind, randomized, controlled trial taking place from 1968 to 1973, suggested that replacing saturated fat with vegetable oil rich in linoleic acid would reduce coronary heart disease and death by lowering cholesterol levels.
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Using unpublished documents and raw data from the original analysis, researchers recently reanalyzed the findings, seemingly disproving the original conclusions.

The data included serum cholesterol levels for 2355 participants exposed to the omega-6 fatty acid diet.

Overall, the researchers observed significant reduction in serum cholesterol in the intervention group compared with controls, but no mortality benefit was observed. In fact, they found a 22% increase in the risk of death for every 30 mg/dL reduction in serum cholesterol in covariate adjusted Cox regression models.

In a meta-analysis of 5 randomized, controlled trials included in the analysis, the cholesterol-lowering interventions were not associated with any benefit to all-cause mortality.

“Available evidence from randomized controlled trials shows that replacement of saturated fat in the diet with linoleic acid effectively lowers serum cholesterol but does not support the hypothesis that this translates to a lower risk of death from coronary heart disease or all causes,” the researchers concluded.

“Findings from the Minnesota Coronary Experiment add to growing evidence that incomplete publication has contributed to overestimation of the benefits of replacing saturated fat with vegetable oils rich in linoleic acid.”

—Michael Potts

Reference:
Ramsden CE, Zamora D, Majchrzak-Hong S, et al. Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment (1968-73) [published online April 12, 2016]. BMJ. doi: http://dx.doi.org/10.1136/bmj.i1246.