The national institutes of health sponsored the diet heart feasibility study to determine if it was possible to lower the blood cholesterol levels of Americans eating at home by changing the kind and amount of fat in their diet. About 1000 men aged 45 to 54 in five cities, all healthy volunteers, were assigned to one of three diets. Diets 1 and 2 were low in cholesterol and saturated fats but high in polyunsaturated fats; that is, they had a higher ratio of polyunsaturated to saturated fats, or P/S ratio. Diet 2 differed from diet 1 in that it contained more polyunsaturated fat and monounsaturated fat. The control diet (diet 3) was similar to a typical American diet, that is, high in cholesterol, total fat, and saturated fat but with low P/S ratio.

The men picked up all their food at special distribution centers. The food containers did not list the ingredients, and neither the participants nor the doctors who conducted the study knew who was assigned to which diet. This research design, called “double blind” is designed to reduce unintentional bias on the part of either the study subjects or the medical scientists, since neither knows who is in what program until the end of the study.

After one year on the assigned diets, the blood cholesterol levels fell between 11% & 12% in the men on diets 1 and 2. The average cholesterol level in the group on the typical American diet fell only 3%.

The next question was ” Will lowering blood cholesterol by diet in healthy Americans decrease the rate of coronary heart disease?” There were several problems in trying to answer this question. First, the symptoms of coronary heart disease usually take four or more decades to manifest themselves. Second, although coronary heart disease is the major cause of death and disability in this country, the actual rate of new cases per year in middle aged people is relatively low, about five to ten new cases per 1000 middle aged male adults. Third, what control group might such a study use?

Ideally, neither the participants nor the staff conducting the study should know which participants are in the treatment group and which are in the untreated control group. Diets that are high or low in animal fat and cholesterol are clearly different, and unless unlabeled foods were given out at a commissary, everyone would realize whether he was assigned to a diet low or high in cholesterol and saturated fat. Because 100,000 men were needed for a definitive diet heart study, it was not feasible to have a blind control group of the necessary size.

Because of these difficulties and a prospective price tag of about one billion dollars, another approach was taken. First, only patients with very high blood cholesterol levels were selected; second, a drug treatment was chosen that lowers the blood cholesterol level to a greater extent than diet alone. This approach reduces the number of participants needed to a manageable level. A drug trial can replace a diet trial, provided that the drug has a specific effect on lowering blood cholesterol (and LDL cholesterol). This permits a direct test of the hypothesis that a decrease in the blood cholesterol level reduces coronary heart disease. Further, a drug trial allows medical scientists to develop a suitable inactive medication or placebo that will not lower the blood cholesterol level, thus permitting the study to be double blind.

About 4,000 healthy middle aged men with high levels of blood total and LDL cholesterol were assigned to either a treatment group, which received an active medication called cholestyramine, or to a control group that received placebo. Cholestyramine was known to produce a significant decrease (10 to 20 percent) in the level of total and LDL cholesterol in the blood. Both the treatment and control groups were put on the same diet. Neither the participants nor the medical staff knew to which of the two groups a participant was assigned. Cholesterol levels were checked every other month. After one year the results of the study were as follows:

Man from group that took active drug: his cholesterol level at the beginning of the trial was 281, and at the end was 199. Man from group that was on placebo starting cholesterol level was 273, and at the end was 274. The men taking the cholestyramine had significantly greater decrease in there blood cholesterol than the men taking placebo. Therefore it is known that you can reduce the risk of coronary heart disease.

Angelo Abruzzese Author How Much Can You Reduce The Risk Of Coronary Heart Disease? Heart Disease