New directions in dietary studies of coronary heart disease.

For several decades the debate on diet and coronary heart disease has been dominated by the classic diet-heart hypothesis, which predicts an adverse effect of dietary saturated fat and cholesterol and a beneficial effect of polyunsaturated fat intake. However, recent research suggests that the diet-heart relationship is much more complex than previously recognized. Antioxidants, and in particular vitamin E, are emerging as potentially useful protective factors, and there is increasing evidence that hyperhomocysteinemia is a risk factor that may be modified by dietary changes. However, substantial data support the notion that the trans fatty acids contained in partially hydrogenated vegetable oils adversely affect the risk of coronary heart disease. Other questions, such as the role of selenium and iron, the ideal amount in the diet of polyunsaturated fat of the n-6 or n-3 group (including fish oil) and how the benefits of a diet high in monounsaturated fat (such as the Mediterranean diet) compare with those of diet low in total fat (such as the traditional Asian diet) remain to be settled.