Effects of medium chain fatty acids (MCFA), myristic acid, and oleic acid on serum lipoproteins in healthy subjects.

In this study we investigated the effects on lipoproteins of medium chain fatty acids (MCFA) and myristic acid relative to those of oleic acid. Thirty-seven women and 23 men consumed a 3-wk run-in diet enriched in oleic acid followed by a 6-wk test diet rich in MCFA (n = 21), myristic (n = 20), or oleic acid (n = 19). Experimental fats were incorporated into solid foods. Total fat intake was 40 En% fat. The dietary compositions were the same except for 10 En%, which was provided by MCFA, myristic, or oleic acids, respectively. With the myristic acid diet, low density lipoprotein (LDL) cholesterol was 0.37 mmol/L higher compared with the oleic acid diet (P = 0.0064 for difference in changes). The MCFA diet increased LDL cholesterol, though not significantly, with 0.23 mmol/L relative to the oleic acid diet (P = 0.0752). Compared with the oleic acid diet, HDL cholesterol concentrations increased with the myristic acid diet by 0.10 mmol/L (P = 0.0273) but not with the MCFA diet. The MCFA diet slightly elevated triacylglycerol concentrations, but responses did not significantly differ between the diets. The MCFA diet significantly decreased the apoA-I to apoB ratio compared with both other diets (P < 0.02). We conclude that MCFA raise LDL cholesterol concentrations slightly and affect the apoA-I to apoB ratio unfavorably compared with oleic acid. Myristic acid is hypercholesterolemic, although less than predicted earlier, and raises both LDL and HDL cholesterol concentrations compared with oleic acid.