REVIEW OF DIETARY INTERVENTION STUDIES - EFFECT ON CORONARY EVENTS AND ON TOTAL MORTALITY

The perfect randomised controlled dieary prevention trial of coronary heart disease has never been done. The best we can do is to look at al l the trials together. Dietary trials should be separated from drug tr ials because they have different characteristics. Fourteen dietary tri als which had disease or death as the end point are collected in this review for a metaanalysis. Three of the trials had two parts (male/fem ale or low fat/increased fish), making a total of 17 trials. All were randomised trials, except the Finnish mental hospital trial which was a 12-year a crossover in two hospitals. The trials were primary or sec ondary, diet only or multifactorial; numbers of subjects range from 52 to 57,460. For total deaths the ratio of intervention/control in all 17 trials is 0.94 (significantly less than 1.00) and for coronary even ts the pooled odds ratio is 0.87. But in the seven trials with most ef fective cholesterol lowering the odds ratios are 0.89 for all deaths a nd 0.70 for coronary events. There is thus no indication of excess all causes mortality in the dietary trials. Four recent secondary prevent ion trials had angiographic endpoints. There were a total of 275 subje cts; trials were in Holland, USA, Germany and UK. In all trials plasma cholesterol was effectively lowered and coronary narrowing regressed a little, or progressed less in the diet group but significantly compa red with controls. These angiographic trials strongly support the resu lts of the major prevention trials. Lastly, a set of ten trials with f ish oil after coronary angioplasty are reviewed. In same there appeare d to be lower rates of restenosis, but not in all. The mechanism here is different from the major trials with plasma cholesterol-lowering di ets for longer periods.