On the basis of European studies, a Mediterranean-style diet has been advocated for preventing heart disease. Although the actual protective mechanisms remain unclear, antioxidants and n-3 fatty acids have been implicated because of their effects on atherosclerosis and thrombosis. Further insights about diet in coronary artery disease could come from studying other non-Western diets. In addition, more information on ethnic diets and heart disease is urgently needed because of rapid increases in coronary artery disease in non-European populations. Singh and colleagues studied the effect of an Indo-Mediterranean diet consisting of whole grains, legumes, fruits, vegetables, nuts, and soybean or mustard oil on coronary artery disease in Indian patients.
They advertised to recruit volunteers 25 years or older who had hypercholesterolemia, hypertension, diabetes mellitus, or a history of heart attack. The presence of cardiac risk factors was confirmed during the intake examination. During the three-week preparatory period, participants recorded food intake, exercise, and other factors. Researchers also met weekly with participants during this period to educate them about the project and to clarify nutritional, laboratory, and other data. Patients were randomly assigned to intervention or control diets and were followed for two years.
Approximately two thirds of the 1,000 patients were vegetarian. All of the patients consumed milk, butter, clarified butter (ghee), and trans fatty acids. All participants were advised to follow the National Cholesterol Education Program step I diet. In addition, those in the intervention group were advised to also consume at least 400 to 500 g of fruits, vegetables, and nuts plus 400 to 500 g of whole grains and three to four servings daily of mustard seed or soybean oil. These recommendations aimed to provide the intervention group with phytochemicals, antioxidants, and alpha-linolenic acid (as a source of n-3 fatty acid) as recommended by the Indian Consensus Group for prevention of hypertension and coronary artery disease.
All participants were advised to walk briskly for up to 4 km (2.5 miles) or to jog for 10 to 15 minutes daily. Participants also were discouraged from smoking or using alcohol and were encouraged to use yoga meditation techniques or breathing techniques for relaxation. Usual medical treatment was continued as directed by the physicians for individual participants.
The groups were stratified by risk or presence of coronary artery disease and were comparable at the beginning of the study. Almost all participants were male, the average age was 49 years, and about one half were smokers. About 22 percent in each group were overweight at the beginning of the study, 73 percent had hypercholesterolemia, 37 percent were hypertensive, and about 20 percent had diabetes. Dietary intake of fruit, vegetables, legumes, and oils increased in both groups but was significantly greater in the intervention group. Lifestyle and exercise changes did not differ between the groups.
After two years, total fruit, vegetable, nut, whole grain, and mustard seed or soybean oil consumption was significantly higher in the 499 patients in the intervention group compared with the 501 patients in the control group. The intervention group also acquired a greater percentage of calories from complex carbohydrates and had a higher polyunsaturated to saturated fat ratio in their diets.
By the end of the study, both groups showed significant decreases in total cholesterol levels, low-density lipoprotein cholesterol levels, and triglycerides, with greater effects in the intervention group. Fasting blood glucose levels, body mass index, and blood pressures were significantly reduced in the intervention group, and high-density lipoprotein levels increased in the intervention group but not in the control group.
Clinically, the intervention group showed significant reductions in cardiac medications, risk of sudden cardiac death, myocardial infarction, and all cardiac end points compared with the control group. Cardiovascular events occurred in 49 patients (10 percent) of the intervention group compared with 96 patients (19 percent) in the control group. In statistical analysis, the cardiac event effect was independent of baseline characteristics.
The authors conclude that an Indo-Mediterranean diet rich in alpha-linolenic acid is associated with a significant reduction in nonfatal myocardial infarction, sudden cardiac death, and total cardiac outcomes. These results were achieved in high-risk patients in spite of difficulties with sustained adherence over at least two years. The diet used was safe, economical, and acceptable, because it was based on locally produced ingredients and cost about $1 per day.