Food Lipids: Chemistry, Nutrition, and Biotechnology

in plasma cholesterol as a function of dietary cholesterol is influenced by baseline
cholesterol intake. A recent epidemiological overview [38] concluded that after one
considered dietary confounders there was no association between egg consumption
at levels up to 1� egg per day and the risk of coronary heart disease in nondiabetic
men and women.
In contrast to dietary cholesterol there is little question that the saturation of
dietary fat exerts a profound influence on blood cholesterol levels. Ahrens et al. [39]
fed a number of subjects a liquid formula diet containing 45% of energy as fat. In
general, plasma cholesterol rose as the fat saturation rose. Keys et al. [40] and
Hegsted et al. [41] studied the effects of changes in dietary fat on change in blood
cholesterol levels in humans and offered formulas to predict changes in cholesterolemia
based on changes in dietary fat. Both groups found fat saturation to have the
greatest effect. Stearic acid did not appear to fit the formula, and direct experiments
in human subjects have shown this to be true [42,43]. Hayes and Khosla [44] have
hypothesized that the two most important fatty acids related to cholesterol levels are
myristic acid (which raises cholesterol levels at every concentration) and linoleic
acid (which exerts an increasing hypocholesterolemic effect until it reaches a dietary
level of 6–7% of energy). Hayes [45] has reviewed these data recently. McNamara
et al. [46] fed normal subjects diets high or low in cholesterol and containing saturated
or unsaturated fat. The major factor determining cholesterolemia was the saturation
of the fat, the influence of which was about four times greater than that of
dietary cholesterol (Table 2). McNamara [47] has reviewed exhaustively the connection
between dietary cholesterol and atherosclerosis. He cites large epidemiological
studies that indicate little connection between cholesterol intake and risk of
coronary heart disease [48,49], emphasizes the role of saturated fat, and suggests
that diets very high in cholesterol reflect an unbalance between intake of fats and of
grains, vegetables, and fruits.
In addition to fatty acid saturation the position of a specific fatty acid in the
triglyceride molecule is important [50]. In an effort to test cholesterolemic effects of
specific fatty acids, McGandy et al. [51] fed human subjects diets that contained fats
into which high levels of specific saturated fatty acids (lauric, myristic, palmitic, or
Table 2 Plasma Cholesterol Levels in Subjects Fed High or Low
Levels of Cholesterol with Saturated or Unsaturated Fat
Fat in diet
Fat
(P/S)
Dietary
(mg)
Cholesterol
Plasma
(mg/dL)
Low cholesterol
Saturated 0.31 � 0.18 288 � 64 243 � 50
Unsaturated 1.90 � 0.90 192 � 60 218 � 46
High cholesterol
Saturated 0.27 � 0.15 863 � 161 248 � 51
Unsaturated 1.45 � 0.50 820 � 102 224 � 46
Source: From Ref. 46.
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.