ArticlesEffect of an Indo-Mediterranean diet on progression of coronary artery disease in high risk patients (Indo-Mediterranean Diet Heart Study): a randomised single-blind trial
Introduction
People of south-Asian origin who live in developed countries have an increased mortality rate and susceptibility to coronary artery disease (CAD) compared with indigenous populations.1, 2, 3 The prevalence of CAD is 10% in urban dwellers, but is low in rural dwellers (3–4%) and the lower social classes (1–3%) who consume a diet based on cereal. The risk shows a graded increase in urban dwellers, high social classes, and immigrants, which is linked to pronounced differences in diet and lifestyle.1, 2, 4, 5 However, the greater susceptibility of people of south-Asian origin to CAD is not explained by conventional risk factors, such as cholesterol and obesity, alone.2, 3 Results from the seven countries study6 showed that such differences in coronary risk can be explained partly by antioxidants in the diet, variations in physical activity, and smoking. Data from epidemiological and cohort studies7, 8 also showed that increased consumption of fruits, vegetables and legumes, grains, nuts, and n-3 fatty acids might be associated with a decreased risk of CAD, and deaths attributable to coronary disease. Results from randomised controlled intervention trials9, 10, 11, 12, 13, 14 suggest that treatment with n-3 fatty acids and antioxidant rich foods such as fish, fruits, vegetables, legumes, and nuts can reduce cardiac events and related mortality in patients with CAD. Evidence suggests that dietary patterns could well have an effect on the mechanisms of atherosclerotic plaque vulnerability and the progression of thrombosis.15, 16, 17
The scientific advisory committee of the American Heart Association (AHA) has stated that a Mediterranean-style diet has impressive effects on the progression of cardiovascular disease.13 Significant findings from the Lyon Heart Study9, 10 and other such studies,11, 12 have prompted an aggressive pursuit of the benefits of such dietary modifications in other regions of the world.11, 12, 15 If the Lyon diet is also of benefit in non-Mediterranean populations, such as south-Asians, it might provide an economically feasible and realistic method to reduce CAD in these regions. The AHA statement13 raised some issues for investigators: geographical and non-measured cultural and social differences in potential target populations; enhanced definition of baseline diets of both trial groups at the beginning of the study; enhanced and continuing analysis of true dietary patterns throughout studies; and an assessment of any changes in combined risk factors during the study. We have addressed some of these issues here. In patients with clinical CAD or with recognised risk factors, we assessed the effect of an Indo-Mediterranean diet consisting of whole grains including legumes, fruits, vegetables, nuts, and mustard or soybean oil.
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Participants
We recruited participants through advertisements in newspapers and local service clubs that invited people older than 25 years with hypercholesterolaemia, hypertension, diabetes mellitus, or heart attack for free medical advice about diagnosis and treatment of their disorders. Patients were enrolled by a dietician and a physician. The diagnostic criteria for these cardiovascular risk factors were those standardised by WHO.18 There were between 50 and 150 respondents at each centre. Most
Results
Participants (n=1000) were randomly assigned to the intervention diet (499) or control diet (501). Because patients were stratified by risk factor or presence of CAD, both groups were comparable for over 30 characteristics, including complications (table 1). Hypertension was a common risk factor in both groups. Hypercholesterolaemia was much the same in the two groups, and for most patients serum cholesterol was between 5·2–6·7 mmol/L. In both groups, roughly half the patients were smokers at
Discussion
Our results show that consumption of an Indo- Mediterranean diet rich in α-linolenic acid was associated with a significant reduction in non-fatal myocardial infarction, sudden cardiac death, and total cardiac endpoints. Additionally, the intervention diet showed improvements in the number of surrogate traditional risk factors, which were better than those seen in controls who adhered to the prudent step I diet.
The intervention diet was based on that suggested by the scientific advisory
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