Lipids

• Some fatty acids and some amino acids are essential
• Humans can synthesise most fatty acids from carbohydrates, but two (cis)-polyunsaturated fatty acids are considered essential
• Alpha-linolenic acid (an omega-3 fatty acid) and linoleic acid (an omega-6 fatty acid) cannot be synthesised by the body
• Humans lack the enzyme required to introduce double bonds at the required position of the carbon chain
• Essential fatty acids are modified by the body to make important lipid-based compounds, such as signalling molecules
• Dietary deficiencies of essential fatty acids may be linked to impaired brain development (e.g. depression) and altered maintenance of cardiac tissue (e.g. abnormal heart function)
• Foods rich in essential fatty acids (omega-3 and omega-6) include fish, leafy vegetables, and walnuts
• Cholesterol in blood as an indicator of the risk of coronary heart disease
• Fats and cholesterol are packaged with proteins (to form lipoproteins) for transport in the bloodstream
• Low-density lipoproteins (LDLs) carry cholesterol from the liver to the body, raising blood cholesterol levels
• High-density lipoproteins (HDLs) carry excess cholesterol back to the liver for disposal, lowering blood cholesterol levels
• The mix of fatty acids consumed as part of a diet directly influences the levels of cholesterol in the bloodstream
• Saturated fats increase LDL levels within the body, raising blood cholesterol levels
• Trans fats increase LDL levels and lower HDL levels, significantly raising blood cholesterol levels
• Cis-polyunsaturated fats raise HDL levels, lowering blood cholesterol levels
• High cholesterol levels in the bloodstream lead to the hardening and narrowing of arteries (atherosclerosis)
• High levels of LDL in the bloodstream lead to the formation of deposits in the walls of the arteries
• The accumulation of fat within the arterial wall leads to the development of plaques, which restrict blood flow
• If coronary arteries become blocked, coronary heart disease (CHD) will result, including heart attacks and strokes