Effect of synthetic triglycerides of myristic, palmitic, and stearic acid on serum lipoprotein metabolism

Abstract

Objectives: To determine relative effects of diets high in synthetic sources of myristic (14:0), palmitic (16:0) or stearic (18:0) acid on concentrations and metabolism of serum lipoproteins.

Design: Eighteen healthy women participated in a three-way cross-over study for five week periods separated by seven week washout periods, diets were assigned in random order.

Subjects: Premenopausal women, not on medication, were from three races (Caucasian, African-American, Asian) and four apolipoprotein E phenotype groups (3/3, 3/2, 4/3, and 4/2).

Intervention: During the first week the subjects consumed a baseline diet providing 11 energy (en)% saturated fat, 10 en% polyunsaturated fat and 14 en% monounsaturated fat. Followed by test diets with 19 en% saturated fat (including 14 en% test saturated fatty acid), 3 en% polyunsaturated fat, and 14 en% monounsaturated fat for four weeks. Synthetic fats (trimyristin, tripalmitin, and tristearin) were used in blends with natural fats and oils.

Results: Mean concentrations of serum total, esterified and LDL cholesterol were significantly lower after 18:0 than after 16:0 (n=16–18, P<0.01 for treatment effect). Myristic acid (14:0) had an intermediate effect. Receptor-mediated degradation of ¹²⁵I-LDL in mononuclear cells obtained from the subjects was lower after 16:0 than after 14:0 and 18:0 (n=16–18, P=0.05 for treatment effect). Differences in the digestibilities of the fats were not a major factor in the results. Strong cholesterolemic responses to the 16:0 diet were partly explained by apoE phenotype.

Conclusions: As noted previously, stearic acid was neutral compared to 14:0 and 16:0. In contrast to studies involving natural fats, 14:0, fed as a synthetic triglyceride, was less cholesterolemic than 16:0 in a majority of subjects. ApoE phenotype influenced the cholesterolemic response particularly when diets high in 16:0 were eaten.

Sponsorship: Funded by United States Department of Agriculture Grant 93-37200-8978.