Background:Many studies have shown that trans fatty acids have unfavorable effects on the serum lipoprotein profile. In general, however, fats were compared with different functional characteristics, which lower the practical applications of the results.Objective:The major aim of this study was to compare the effects of a high-palmitic acid, trans-free semiliquid fat with those of a high-oleic acid, low-trans semiliquid fat on the serum lipoprotein profile of healthy subjects.Subjects and design:Forty-four subjects (33 women and 11 men) consumed, in random order, two experimental diets, each for 3 weeks. Diets provided 40 energy percent (En%) from fat, while 15 En% was supplied by the experimental fats. At the end of each intervention period, concentrations of serum lipoproteins, C-reactive protein, glucose and insulin were measured.Results:When subjects consumed the high-oleic acid, low-trans semiliquid fat, intakes of stearic acid (+1.3 En%), oleic acid (+2.9 En%), alpha-linolenic acid (+0.1 En%) and trans fatty acids (+0.6 En%) were higher and that of palmitic acid (-4.2 En%) lower. Serum concentration of low-density lipoprotein cholesterol decreased by 0.34+/-0.39 mmol/l (mean+/-s.d.; 95% confidence interval (CI), -0.46 to -0.23 mmol/l; P<0.001) and high-density lipoprotein (HDL) cholesterol by -0.06+/-0.17 mmol/l (95% CI, -0.11 to -0.01 mmol/l; P=0.021). Also, the total to HDL cholesterol ratio was lower (-0.15+/-0.34; 95% CI, -0.25 to -0.05; P=0.006). Other parameters did not change.Conclusions:A high-oleic acid, low-trans semiliquid fat has a more favorable effect on the serum lipoprotein profile than a trans-free semiliquid fat with comparable functional characteristics, but high in palmitic acid.