Studies for CHD Prevention

A consequence of the lipid hypothesis of CHD is that reduction of saturated fat and cholesterol and an increase of polyunsaturated fatty acids in the diet will lower plasma cholesterol level with a reduction in the risk of CHD. A causal relation between dietary fat and CHD can be established only by conducting randomized clinical trials. 

There have been three primary and eight secondary prevention trials in which dietary change was the only variable. Dietary modification included reduction in total fat, substitution of saturated fat by polyunsaturated oils and reduction in cholesterol intake. These changes resulted in a reduction of saturated fat intake by 27 55% and reductions in plasma cholesterol of up to 18%. However, with the exception of one study, the Lyon Diet Heart Study (de Lorgeril et al., 1994), neither total or CHD mortality was lowered significantly by the dietary interventions (Ravnskov, 1998 Parodi, 2004). In the successful Lyon Diet Heart Study, a Mediterranean-type diet was compared with the usual post-infarct prudent diet. Throughout this trial, plasma cholesterol levels were similar in both the treatment and control groups. 

Multiple studies have examined the effect of dietary modification plus various lifestyle changes or drug therapy on CHD outcome and total mortality. Muldoon et al. (1990), Ravnskov (1992), and Davey Smith et al. (1993) conducted meta-analyses of these trials. Overall, there was a small benefit for nonfatal CHD, which was more noticeable in high-risk patients, but not for CHD or total mortality. 

Bucher et al. (1999) conducted a systematic review of the benefit of different classes of cholesterol-lowering drugs for prevention of CHD and total mortality. Only the statin drugs showed a statistically significant reduction in mortality from CHD and from all causes. 

Statin Drugs and CHD. Statin drugs are 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors that act by inhibiting HMG-CoA reductase, the rate-limiting step in cholesterol biosynthesis. The statins are now the most commonly prescribed drugs for the treatment of hypercholesterolemia. They can reduce plasma total cholesterol by 20-42%, LDL-cholesterol by 25-55% and triglycerides by 10-35%. In addition, 

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