Dietary oils, serum lipoproteins, and coronary heart disease.

Variable amounts of olive oil rather than hard fats were used in classic Mediterranean diets. We review the effects of replacing hard fats with olive oils or starchy foods on blood lipoprotein concentrations. The saturated fatty acids lauric, myristic, and palmitic acids raise both low-density lipoprotein (LDL) and high-density lipoprotein (HDL) somewhat compared with oleic acid. If any fat is replaced by carbohydrates, fasting triglyceride values rise and HDL concentrations fall; effects on LDL depend on the type of fat that is being replaced. Trans isomers of oleic acid lower HDL and raise LDL and lipoprotein(a). The fatty acids in unhydrogenated fish oil potently lower triglycerides but may raise LDL somewhat. When body weight is forcibly kept constant, substitution of unsaturated oils such as olive oil for hard fats rich in saturated or trans fatty acids will produce a more favorable lipoprotein profile than replacement of fat by carbohydrates. However, high-oil diets might lead to obesity, which would undo their favorable effects.