Saturated fatty acids total diet content effect

There is substantial evidence that indicates that dietary fat can influence significantly not only serum levels of cholesterol and triacylglycerols but also the lipid composition and content of Apoproteins (156-159). Much attention has been placed on the effects of diet on LDL levels, and saturated fatty acid and cholesterol itself have been identified as the major nutritional factors that can raise serum LDL-cholesterol levels. However, LDL cholesterol is only one of the many risk factors for atherosclerosis, and it is not known if oxidative modification of LDL is an equally or more important factor in the pathogenesis of atherosclerosis than total LDL cholesterol per se. More longitudinal studies are needed to answer these questions. If lipid peroxidation is a major risk factor for atherosclerosis, then excess consumption of highly unsaturated fats may not be advisable. 

The replacement of saturated fatty acids with polyunsaturated fatty acids is generally accompanied by a lowering of plasma total cholesterol and LDL cholesterol. Linoleic acid reverses the effects of saturated fatty acids in raising blood triacylglycerols and LDL. Although the results of many studies are inconsistent, most studies show that plasma HDL cholesterol levels tend to decrease when the saturated fatty acids in the diet are replaced with polyunsaturated fatty acids. However, the level of HDL cholesterol tends to be slightly raised by the saturated fatty acid content of the diet. 

Coronary heart disease. The role of fatty acids in coronary heart disease is related to their effects on blood total cholesterol and lipoprotein cholesterol levels. It has been well documented that saturated fatty acids in our diets (mainly palmitic acid) are responsible for raising blood total cholesterol and LDL cholesterol levels and that decreases in total and LDL cholesterol can be achieved by reducing the content of saturated fat in the diet (for review, see Grundy, 1986a McNamara, 1987b). This saturated fatty acid effect is due partly to alterations in cholesterol synthesis and also to changes in lipoprotein synthesis... 

Saturated fatty acids as a group affect factors involved in cholesterol metabolism. Relative to the carbohydrate content of the diet, a decrease in saturated fat content induces a favorable decrease in serum total and LDL cholesterol concentrations but unfavorably reduces HDL cholesterol concentrations. Both increasing and decreasing effects of saturates on platelet aggregation have been observed, as well as the absence of effect, so results are inconsistent and difficult to interpret. Whether the beneficial effect of a diet low in saturated fat on the prethrombotic state of blood depends on the dietary fiber content is still unclear. 

When discussing the health effects of the total saturated fat content of diets, this class of fatty acids has to be compared with some other component of the diet that provides a similar amount of energy (isoenergetic). Otherwise, two variables are being introduced changes in total dietary energy... 

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