From the Guidelines
Saturated fats increase the risk of atherosclerosis primarily through their effects on blood lipid profiles and inflammatory processes, whereas unsaturated fats, especially polyunsaturated and monounsaturated fats, tend to improve the LDL:HDL ratio, reduce inflammation, and enhance endothelial function. The pathophysiology underlying this difference involves the impact of these fats on low-density lipoprotein (LDL) cholesterol levels and the inflammatory response in the arterial walls. When consumed in excess, saturated fats raise levels of LDL cholesterol in the bloodstream, particularly the small, dense LDL particles that can more easily penetrate arterial walls 1. These LDL particles become oxidized and trigger an inflammatory response, leading to the recruitment of macrophages that engulf the oxidized LDL and transform into foam cells. This process initiates the formation of fatty streaks in the arterial intima, the first step in atherosclerotic plaque development.
Some key points to consider in the pathophysiology of saturated versus unsaturated fats and atherosclerosis include:
- The role of omega-3 polyunsaturated fatty acids in reducing inflammation and triglyceride levels, as well as their potential to decrease the risk of cardiovascular disease 1.
- The benefits of monounsaturated fats in maintaining HDL levels while lowering LDL, which contributes to a reduced risk of atherosclerosis 1.
- The importance of considering the food sources of these fats, as the overall dietary pattern and the presence of other nutrients and bioactive compounds can influence their metabolic effects 1.
- The need for a balanced approach to dietary recommendations, taking into account the complexity of the relationship between diet and atherosclerosis, as well as the limitations of current evidence 1.
Overall, the evidence suggests that replacing saturated fats with unsaturated fats, particularly polyunsaturated and monounsaturated fats, can help reduce the risk of atherosclerosis and improve cardiovascular health. The most recent and highest quality studies support the recommendation to limit saturated fat intake and emphasize the benefits of unsaturated fats in preventing atherosclerosis 1.
From the Research
Pathophysiology of Saturated Fats and Atherosclerosis
- The pathophysiology explaining why saturated fats versus unsaturated fats increase the risk of atherosclerosis is complex and involves multiple mechanisms 2, 3, 4.
- A diet high in saturated fatty acids (SFA) is suspected to contribute to atherosclerotic cardiovascular disease (ASCVD) risk, primarily by raising low-density lipoprotein cholesterol (LDL-C) concentrations 2.
- Higher intakes of SFA may also influence pathways affecting inflammation, cardiac rhythm, hemostasis, apolipoprotein CIII production, and high-density lipoprotein function, although the impacts of these effects on ASCVD risk remain uncertain 2.
Comparison of Saturated and Unsaturated Fats
- Replacing SFA with unsaturated fatty acids, particularly polyunsaturated fatty acids, may reduce ASCVD risk 2, 3.
- Reducing dietary saturated fat has been shown to reduce the risk of combined cardiovascular events by 21% 3.
- The evidence suggests that replacing the energy from saturated fat with polyunsaturated fat or carbohydrate appears to be a useful strategy for reducing cardiovascular risk 3, 4.
Mechanisms of Atherosclerosis
- High serum levels of low-density lipoproteins (LDL) play a main role in the initiation and progression of atherosclerosis 5.
- Excess LDL introduces chaos in the vascular wall, leading to thrombotic complications, while functional high-density lipoproteins (HDL) facilitate the resolution of this vascular chaos by suppressing atherosclerosis progression and inducing regression 5.
- Dietary measures to lower levels of LDL-C and triglyceride, such as minimizing saturated fats and refined carbohydrates, eliminating trans-fat, and increasing fruits, vegetables, whole grains, low-fat dairy, and fish or other omega-3 fatty acids, can help reduce cardiovascular risk 6.