OBJECTIVE: To assess the effect of reduction or modificationof dietary fat intake on total and cardiovascular mortality and cardiovascularmorbidity.
DESIGN: Systematic review.
DATA SOURCES: Cochrane Library, Medline, Embase, CAB abstracts,SIGLE, CVRCT registry, and biographies were searched; trials known to experts wereincluded.
INCLUDED STUDIES: Randomised controlled trials stating intention to reduce or modify fat or cholesterol intake in healthy adult participants over at least six months. Inclusion decisions, validity,and data extraction were duplicated. Meta-analysis (random effects methodology), meta-regression, and funnel plots were performed.
RESULTS: 27 studies (30 902 person years of observation) were included. Alteration of dietary fat intake had small effectson total mortality (rate ratio 0.98; 95% confidence interval 0.86to 1.12). Cardiovascular mortality was reduced by 9% (0.91; 0.77to 1.07) and cardiovascular events by 16% (0.84; 0.72 to 0.99),which was attenuated (0.86; 0.72 to 1.03) in a sensitivity analysis that excluded a trial using oily fish. Trials with at least two years' follow up provided stronger evidence of protection from cardiovascular events (0.76; 0.65 to 0.90).
CONCLUSIONS: There is a small but potentially important reduction in cardiovascular risk with reduction or modification of dietary fat intake, seen particularly in trials of longer duration.