IMPACT OF MYRISTIC ACID VERSUS PALMITIC ACID ON SERUM-LIPID AND LIPOPROTEIN LEVELS IN HEALTHY WOMEN AND MEN

The cholesterol-raising effect of dietary saturated fatty acids is largely accounted for by lauric, myristic, and palmitic acids. Dairy fat is a major source of myristic acid, and palm oil is especially rich in palmitic acid. Myristic acid is suspected of being much more cholesterolemic than palmitic acid, but direct comparisons have been lacking. We therefore fed 36 women and 23 men three diets that differed from each other in palmitic, oleic, and myristic acid content by about 10% of total energy. We used palm oil, high-oleic acid sunflower oil, and a specially produced high-myristic acid fat to achieve these differences. Each diet was consumed for 3 weeks in random order. Mean serum cholesterol was 4.53 mmol/L on the high-oleic acid diet, 4.96 mmol/L on the palmitic acid diet, and 5.19 mmol/L on the myristic acid diet (P<.0001 for all comparisons). Myristic acid raised low-density lipoprotein (LDL) cholesterol by 0.11 mmol/L, high-density lipoprotein (HDL) cholesterol by 0.12 mmol/L, and apolipoprotein (apo) A-I by 7.2 mg/dL relative to palmitic acid; increases relative to oleic acid were 0.50 mmol/L for LDL cholesterol 0.15 mmol/L for HDL cholesterol, 6.0 mg/dL for apoB, and 8.9 mg/dL for apoA-I (P<.01 for all comparisons). The HDL cholesterol and apoA-I levels on the palmitic and oleic acid diets were the same. None of the responses differed significantly between women and men. Myristic acid and palmitic acid both caused high LDL cholesterol and apoB levels and low HDL to LDL ratios. Thus, diets for the treatment of hypercholesterolemia should be low in myristic and palmitic acids.