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

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 chdesteiol, though not significantly, with 0.23 mmol/L relative to the okic acid diet (P = 0.0752). Compared with the oleic acid &et, HDL cholesterol concentrations increased with the mpi&e acid diet by 0.10 mmol/L ( P = 0.0273) but not with the MCFAdiit. The MCFA diet slightly elevated triacylglyceror concentrations, but responses did not significantly differ between the diets. The MCFA diet significantly decreased the apA-I to apoB ratio compared with both other diets ( P < 0.02).1 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.-Temme, E. H. M., R. P. Mensink, and G. Homstra. Effects of medium chain fatty acids (MCFA), myristic acid, and oleic acid on serum lipoproteins in healthy subjects. J. Lipid Res. 1997. 3 8 1746-1754. Supplementary key words saturated fatty acids MCFA myristic acid oleic acid lipoproteins cholesterol apolipoproteins healthy humans Medium chain fatty acids (MCFA) that have between six and ten carbon atoms are not only used in diets for patients with malabsorption disorders, but also in structured lipids like caprenin (50% caprylic acid (C8:O) plus capric acid (C10:0), and 45% behenic acid (C22: 0)). After absorption, the transport of MCFA through the blood differs from longer chain fatty acids. MCFA are not incorporated into triacylglycerols packaged with chylomicrons as longer chain fatty acids are, but are transported primarily through the portal vein to the liver and provide the body with a rapid source of energy ( 1 ) . It has been suggested that effects of MCFA on serum cholesterol are similar to those of carbohydrates ( 2 ) , but whether the effects of MCFA on different lipoproteins are indeed comparable remains to be determined. Studies carried out to investigate effects of MCFA on lipoproteins found total cholesterol levels similar to concentrations on western diets (3-5), increased triacylglycerol concentrations (3, 4), and decreased HDL concentrations (3,5). These studies, however, were of short duration (3) and were carried out with a limited number of subjects (4, 6) . In addition, the amount of MCFA was not the only variable among the experimental diets (3-7). Certain edible fats like coconut oil, palm kernel oil, and butterfat do not only contain considerable amounts of MCFA, but are also rich in myristic acid. Myristic acid might be the most potent cholesterol-raising fatty acid (8, 9). Recent studies in healthy volunteers consuming diets enriched in myristic acid, however, yielded contradictory results (10, 1 1 ) . Compared to palmitic acid, myristic acid raised total, LDL and HDL cholesterol in one study (10) but only increased HDL cholesterol concentrations in another (1 1). In both studies, however, myristic acid was less cholesterolemic than predicted by the formula developed by Hegsted et al. (8). We, therefore, decided to compare in healthy volunteers the effects on serum lipids and lipoproteins of an MCFAand a myrisAbbreviations: apo, apolipoprotein; CETP, cholesteryl ester transfer protein; CI, confidence interval; En%, percent of energy; HDL, high density lipoprotein; LDL, low density lipoprotein; Lp[a], lip* protein[a]; MCFA, medium chain fatty acids; MCT, medium chain triglycerides. 1746 Journal of Lipid Research Volume 38, 1997 by gest, on A uust 7, 2017 w w w .j.org D ow nladed fom tic acid-enriched diet with those of a diet enriched in oleic acid. SUBJECTS AND METHODS