Objective Previous systematic reviews were not restricted to either primary or secondary prevention trials, this study aimed to investigate the effects of reduced and/or modified fat diets and dietary fatty acids on all-cause mortality, cardiovascular mortality and cardiovascular events in participants with established coronary heart disease.

Design Systematic review, meta-analysis and univariate/multivariate meta-regression.

Eligibility and criteria for selecting studies Electronic searches for randomised controlled trials comparing reduced/modified fat diets versus control diets were performed in MEDLINE, EMBASE and the Cochrane Library.

Data extraction Pooled effects were calculated using an inverse-variance random effect meta-analysis. Random effects univariate and multivariate meta-regressions were performed including changes in all types of dietary fatty acids.

Results Overall, 12 studies enrolling 7150 participants were included in the present systematic review. No significant risk reduction could be observed considering all-cause mortality (relative risk (RR) 0.92, p=0.60; I²=59%) and cardiovascular mortality (RR 0.96, p=0.84; I²=69%), combined cardiovascular events (RR 0.85, p=0.30; I²=75%) and myocardial infarction (RR 0.76, p=0.13; I²=55%) comparing modified fat diets versus control diets. This results could be confirmed for the reduced fat versus control diets (RR 0.79, p=0.47; I²=0%), (RR 0.93, p=0.66; I²=0%), (RR 0.93, p=0.71; I²=57%) and (RR 1.18, p=0.26; I²=18%). The multivariate and univariate model showed no significant associations between the independent variables and the changes from saturated fat, monounsaturated fat, polyunsaturated fat and linoleic acid. Sensitivity analyses did not reveal a significant risk reduction for any outcome parameter when polyunsaturated fat was increased in exchange for saturated fat.

Conclusions The present systematic review provides no evidence (moderate quality evidence) for the beneficial effects of reduced/modified fat diets in the secondary prevention of coronary heart disease. Recommending higher intakes of polyunsaturated fatty acids in replacement of saturated fatty acids was not associated with risk reduction.