There is little debate that an elevated plasma cholesterol level, specifically an elevated plasma LDL cholesterol level, increases cardiovascular disease risk.2,4 Data from inter- and intrapopulation studies have clearly demonstrated that as total and LDL cholesterol levels increase, cardiovascular disease risk increases. Although this relationship is generally accepted, the specifics of the relationship generate debate. Relevant questions pertain to the actual level of plasma cholesterol at which cardiovascular disease risk is increased, whether the relationship holds true across all age groups and both sexes, and what contributions plasma HDL levels and the plasma LDL/HDL ratio make to cardiovascular disease risk independent of plasma LDL levels. Irrespective of these uncertainties, the evidence that elevated plasma LDL cholesterol levels constitute an independent risk factor for cardiovascular disease has been a major component in studying the genetic and environmental factors involved in hypercholesterolemia. Epidemiologic data reveal relationships between a number of dietary elements and elevated plasma cholesterol levels with the strongest relationships between dietary fatty acids, plasma cholesterol levels, and cardiovascular disease incidence. The data from a variety of epidemiologic investigations, both cross-cultural and cross-sectional, indicate that plasma total cholesterol levels are increased by saturated fat intake and obesity. HDL cholesterol levels are decreased by intakes of low-tat, high-carbohydrate diets, a high BMI, and lack of activity and increased by intake of dietary fat, alcohol, and physical activity. Controlled clinical trials have provided verification of these epidemiologic observations in practically every case. Based on the available data, it can be predicted that for every 1% decrease in saturated fat calories and 1% increase in carbohydrate calories, plasma total cholesterol levels will decrease 1.7 mg/dl (0.8%) and HDL cholesterol levels will fall 0.3 mg/dl (0.7%). In contrast, for every 1 kg/m2 decrease in the BMI (a weight loss of approximately 3 kg), total cholesterol levels will decrease 2.8 mg/dl (1.3%) and HDL levels will increase 0.6 mg/dl (1.3%). There have been numerous dietary recommendations provided to the public as part of a population based coronary heart disease risk reduction program,9-12 and in general they have a similar message: reduce total and saturated fat intake to 30% of calories, reduce dietary cholesterol intake, maintain ideal body weight, and exercise. Finally, studies of genetic variations and polymorphisms in the apolipoproteins, the enzymes involved in the intravascular processing of the lipoproteins, and the lipoprotein receptors are essential in order to define the metabolic heterogeneity of the plasma lipoprotein responses to dietary factors. Studies of how various patterns of metabolic responses relate to the role of dietary factors in coronary heart disease risk and to the efficacy of dietary interventions in reducing cardiovascular disease risk in different subgroups of the population are also crucial.80-83 The genetic heterogeneity within populations no doubt contributes to the difficulties in defining the effects of various dietary factors on plasma lipoprotein levels and cardiovascular disease incidence within those populations. It also possibly accounts for the relatively small percentage of the variances in plasma cholesterol levels that can be attributed to the dietary variables observed in many epidemiologic studies.24 What conclusions can one draw from the large amount of epidemiologic data available relating diet, hyperlipidemia, and arteriosclerosis? First, it is important to note that the data from epidemiologic studies do not provide evidence to justify excluding any food items from the diet; no studies document good foods or bad foods relative to plasma cholesterol levels or coronary heart disease risk. Second, the conclusions that can be drawn from the data are fairly straightforward and very logical: eat a variety of foods in moderation, which will result in a dietary pattern relatively low in saturated fat and high in complex carbohydrates and fiber, maintain a healthy relative body weight by balancing caloric intake with caloric expenditure, sustain a level of physical active consistent with good health,84 and enjoy a glass or two of wine with meals.
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