Food Lipids: Chemistry, Nutrition, and Biotechnology

studied in detail for the first time by Bonanome and Grundy [17]. From that study
it was concluded that stearic acid exerted similar effects on the plasma lipoprotein
profile as oleic acid, a monounsaturated fatty acid. However, palmitic acid was
clearly hypercholesterolemic relative to stearic acid (Fig. 5).
2. Monounsaturated Fatty Acids
The most abundant monounsaturated fatty acid in the human diet, oleic acid, has 18
carbon atoms and one double bond. Although olive oil probably is the most wellknown
source of oleic acid, animal fats are in many countries a major contributor
to total oleic acid, but also to palmitic and stearic acid, intake.
a. Oleic Acid. Effects of monounsaturated fatty acids on plasma total cholesterol
levels are often described as neutral. This term is often misinterpreted. It does not
mean that the plasma total cholesterol level does not change when monounsaturates
are added to the diet. Neutral indicates that monounsaturated fatty acids have the
same effect on plasma total cholesterol as compared with an isocaloric amount of
carbohydrates. Although this may be correct for plasma total cholesterol levels, oleic
acid and carbohydrates do not have similar effects on the distribution of cholesterol
of the various lipoproteins [18] (Fig. 6). This was also shown in a study with young,
healthy volunteers [19]. Increasing the intake of oleic acid at the expense of carbohydrates
increased plasma HDL cholesterol concentrations and decreased those of
triacylglycerols. The increase in HDL cholesterol was compensated for by a decrease
in VLDL cholesterol. Effects of carbohydrates and oleic acid on plasma total and
LDL cholesterol concentrations were comparable.
Figure 6 Effects of carbohydrates and palmitic acid on plasma total, LDL cholesterol,
HDL cholesterol, and triacylglycerol concentrations relative to those of cis-monounsaturated
fatty acids (oleic acid). Seven men received three liquid formula diets, each for 3 weeks, in
random order. The composition of the diets was identical, except for 19% of daily energy
intake, which was provided as carbohydrates, palmitic acid (C16:0), or oleic acid (cis-
C18:1) [18].
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.