Evidence from randomised controlled trials did not support the introduction of dietary fat guidelines in 1977 and 1983: A systematic review and meta-analysis

Abstract

Objectives: National dietary guidelines were introduced in 1977 and 1983, by the United States (US) and United Kingdom (UK) governments respectively, with the ambition of reducing coronary heart disease (CHD) by reducing fat intake. To date, no analysis of the evidence base for these recommendations has been undertaken. The present study examines the evidence from randomised controlled trials (RCTs) available to the US and UK regulatory committees at their respective points of implementation. Methods: A systematic review and meta-analysis were undertaken of RCTs, published prior to 1983, which examined the relationship between dietary fat, serum cholesterol and the development of CHD. Results: 2,467 males participated in 6 dietary trials: 5 secondary prevention studies and 1 including healthy subjects. There were 370 deaths from all-cause mortality in both the intervention and control groups. The risk ratio (RR) from meta-analysis was 0.996 (95% CI 0.865 to 1.147). There were 207 and 216 deaths from CHD in the intervention and control groups respectively. The RR was 0.989 (95% CI 0.784 to 1.247). There were no differences in all-cause mortality and non-significant differences in CHD mortality, resulting from the dietary interventions. Mean serum cholesterol levels decreased in both control and intervention groups. This did not result in any subsequent reductions in CHD deaths or all-cause mortality. Government dietary fat recommendations were untested in any trial prior to being introduced. Conclusions: Dietary recommendations were introduced for 220 million US and 56 million UK citizens by 1983, in the absence of supporting evidence from RCTs.