The Sydney Diet Heart Study: a randomised controlled trial of linoleic acid for secondary prevention of coronary heart disease and death

Objective To evaluate the effectiveness of replacing saturated fat (SFA) with omega‐6 linoleic acid (LA) for the secondary prevention of coronary heart disease (CHD) and death. Background Advice to substitute polyunsaturated fats (PUFAs) for SFA is a cornerstone of dietary guidelines. However, clinical CHD benefits of the most abundant PUFA, omega‐6 LA have not been established. A complete analysis of the effects of LA on CHD and CVD mortality has not previously been possible due to missing data from the Sydney Diet Heart Study (SDHS). We recovered the original SDHS dataset to fill two key evidence gaps by (1) reporting unpublished CHD and CVD mortality outcomes, and (2) updating our incomplete 2010 meta‐analysis of LA intervention trials. Design Randomised controlled trial in 458 men with CHD. Interventions The intervention group replaced SFA with LA from safflower oil and safflower oil polyunsaturated margarine. The control group continued their habitual diet. Results The intervention group had higher all‐cause (HR 1.62; 95%CI 1.00–2.64; p=0.051), CVD (HR 1.70; 95%CI 1.03–2.80; p=0.037) and CHD mortality (HR 1.74; 95%CI 1.04–2.92; p=0.036). An updated meta‐analysis of LA intervention trials showed concordant unfavorable effects for CHD and CVD death. Conclusions Substituting LA in place of SFA increased all‐cause, CVD and CHD mortality. Advice to increase LA or unspecified PUFAs merits reconsideration.