What are the most potent LDL cholesterol-raising
nutrients in the diet?

Saturated fatty acids

Explanation Points:

1.      A dietary fat is composed of a mixture of saturated, monounsaturated, and polyunsaturated fatty acids.  The predominant fatty acid in a fat determines the fat's effect on serum lipid and lipoprotein concentrations.

2.      Saturated fatty acids raise LDL cholesterol levels compared to monunsaturates and polyunsaturates.  Thus, butter,composed predominantly of saturated fatty acids, raise LDL cholesterol relative to olive oil, which is composed predominantly of monounsaturated fatty acids.

3.      The serum cholesterol-raising effect of saturated fatty acids is greater than that of dietary cholesterol.

4.      Mechanism:  Saturated fatty acids raise serum LDL cholesterol because they suppress hepatic LDL receptor activity.  Replacement of saturated fatty acids with mono- or poly-unsaturated fatty acids (or with carbohydrate) removes this suppression.

5.      Exception: Stearic acid (C18:0) is the only saturated fatty acid that does not raise LDL cholesterol.  The reason is that after absorption, stearic acid is desaturated to C18:1; hence, the action of stearic acid in the liver is that of a monounsaturated fatty acid.

References:

Grundy SM, Denke MA.  Dietary influences on serum lipids and lipoproteins.  Journal of Lipid Research 1990; 31: 1149-1172.

Cater NB, Garg A.  Serum low-density lipoprotein response to modification of saturated fat intake:  recent insights.  Current Opinion in Lipidology 1997; 8: 332-336.

Mensink RP, Katan MB.  Effect of dietary fatty acids on serum lipids and lipoproteins: meta-analysis of 27 trials.  Arteriosclerosis and Thrombosis 1992; 12: 911-919.