Diet and heart disease. The role of fat, alcohol, and antioxidants.

Overwhelming evidence indicates that the Western diet plays a major role in atherogenesis. Clinicians are only now beginning to tease out the precise components of the diet that are harmful or beneficial. With respect to fat intake, it remains unclear whether it is the amount or type of fat that promotes atherosclerotic disease. There appears to be a consistent positive association of cholesterol, saturated fat, and possibly trans-fatty acid intake and atherosclerotic disease. Although there is general agreement that reducing intake of these dietary components would be beneficial, controversy remains on what should replace these harmful fats. Some researchers advocate massive reductions in total fat consumption with replacement with carbohydrates for everyone, whereas others recommend a Mediterranean-style diet, which replaces saturated animal fats with vegetable fats. Very low-fat diets have been shown to lower the chance of a heart attack among those with severe coronary artery disease, but for the majority of Americans who do not have obvious artery disease, there is no convincing evidence that a very low-fat diet is optimal. There may be other adverse health effects of this Asian diet, such as increased rates of hemorrhagic stroke. Further research is required to refine thinking on the optimal composition of fats in diet. The effects of alcohol consumption on chronic diseases are complex. The strength and consistency of the observational and experimental evidence strongly suggests a causal link between light to moderate alcoholic beverage consumption and reduced risks of CHD. These reductions in risk of CHD appear to be mediated largely by raising HDL cholesterol levels, although additional mechanisms remain possible and do not appear to be beverage specific. Maximal benefit in terms of CHD appears to be at the level of one drink per day. From a public policy standpoint, whether the benefits for CHD persist at heavy drinking levels or are attenuated is moot because clear harm of heavy drinking in terms of overall mortality outweighs any benefits in the reduction of heart disease. Although the association of alcohol and CHD is likely to be causal, any individual or public health recommendations must consider the complexity of alcohol's metabolic, physiologic, and psychological effects. With alcohol, the differences between daily intake of small to moderate and large quantities may be the difference between preventing and causing disease. A discussion of alcohol intake should be a part of routine preventive counseling. Given the complex nature of alcohol disease relationships, alcohol consumption should not be viewed as a primary preventive strategy; also, it should not necessarily be viewed as an unhealthy behavior. Based on the totality of available evidence, antioxidants represent a possible but as yet unproven means to reduce risks of cardiovascular disease. Although it remains unclear whether supplementation of diet with antioxidant vitamins will reduce risks of atherosclerotic disease, most researchers agree that consumption of fruits and vegetables is an important part of a healthy diet. The U.S. Department of Agriculture recommends two to four servings of fruit and three to five servings of vegetables per day.