Dietary Linoleic Acid for Secondary Prevention of Coronary Heart Disease and Death in the Sydney Heart Study: an RCT

The substitution of polyunsaturated fatty acids (PUFA) for saturated fatty acids (SFA) is a cornerstone of worldwide dietary advice for coronary heart disease (CHD) risk reduction. However, clinical CHD benefits specific to the omega-6 PUFA linoleic acid (LA), and distinct from omega-3 PUFAs, have not been established. The Sydney Diet-Heart Study (SDHS; 1966-1973) was a randomized controlled secondary CHD prevention trial testing whether selectively increasing omega-6 LA from safflower oil in place of SFA reduced CHD and improved survival. A full analysis of mortality outcomes has not been published. The investigators recovered the original SDHS dataset, which included detailed longitudinal dietary, smoking and coded mortality data, permitting evaluation of smoking relapse rates, and all-cause, CVD and CHD mortality outcomes by nutrient intake and duration of diet exposure. Data recovery also permitted the first complete meta-analysis of LA intervention trials on mortality outcomes.

Objectives are (1) to evaluate whether increasing dietary linoleic acid alters CVD and CHD mortality, and (2) to assess whether changes in smoking relapse rates contribute to observed mortality differences.