The saturated fatty acids are derived from both animal fats and plant oils. Rich sources of dietary saturated fatty acids include butter fat, meat fat, and tropical oils (palm oil, coconut oil, and palm kernel oil). Saturated fatty acids are straight-chain organic acids with an even number of carbon atoms (Table 2). All saturated fatty acids that have from eight to 16 carbon atoms raise the serum LDL cholesterol concentration when they are consumed in the diet. In the USA and much of Europe, saturated fatty acids make up 12–15% of total nutrient energy intake.

The mechanisms whereby saturated fatty acids raise LDL cholesterol levels are not known, although available data suggest that they suppress the expression of LDL receptors. The predominant saturated fatty acid in most diets is palmitic acid (C16:0); it is cholesterol-raising when compared with cis-monounsaturated fatty acids, specifically oleic acid (C18:cis1 n-9), which is considered to be ‘neutral’ with respect to serum cholesterol concentrations. In other words, oleic acid is considered by most investigators to have no effect on serum cholesterol or lipoproteins. Another saturated fatty acid, myristic acid (C14:0), apparently raises LDL cholesterol concentrations somewhat more than does palmitic acid, whereas other saturates – lauric (C12:0), caproic (C10:0), and caprylic (C8:0) acids – have a somewhat lesser cholesterol-raising effect. On average, for every 1% of total energy consumed as cholesterol-raising saturated, fatty acids, compared with oleic acid, the serum LDL cholesterol level is raised about 2 mg dl−1 (0.025 mmol l−1).

One saturated fatty acid, stearic acid (C18:0), does not raise serum LDL cholesterol concentrations. The main sources of this fatty acid are beef tallow and cocoa butter. The reason for its failure to raise LDL cholesterol concentrations is uncertain, but may be the result of its rapid conversion into oleic acid in the body.