Dietary Alpha-linolenic acid is as effective as oleic acid and linolenic acid in lowering blood cholesterol in normolipidemic men.
Dietary Alpha-linolenic acid is as effective as oleic acid and linolenic acid in lowering blood cholesterol in normolipidemic men.
Year: 1991
Authors: J K Chan, V M Bruce, B E McDonald.
Publication Name: Am J Clin Nutr.
Publication Details: Volume 53; Page 1230.
Abstract:
It is well established that dietary fatty acids influence plasma cholesterol and lipoprotein concentrations, which are major indicators for risk of coronary heart disease (CHD). It is also well documented that saturated fatty acids (SFA – lauric, myristic, and palmitic) are hypercholesterolemic, while linoleic acid (LA), an unsaturated n6 fatty acid, is hypocholesterolemic. Studies have also reported that oleic acid (OA), a monounsaturated fatty acid (MUFA), is as effective as LA in lowering plasma cholesterol concentrations. This study was one of the first to assess whether alpha-linolenic acid (ALA) is as effective as OA and LA in lowering blood cholesterol. In addition to cholesterol and lipoprotein values, plasma apolipoprotein concentrations were also analyzed as an accurate method of determining the atherogenic properties of dietary fats. This study consisted of two 48 day phases with a 2 month break between each phase. Each phase was further divided into four periods: a 6 day pre-experimental period, two 18 day experimental periods, and a 6 day post-experimental period. All diets were identical except for sources of added fat. All diets provided 3200 kcal/day, of which 53% was carbohydrate, 13% protein, and 34% fat. All subjects were fed a mixed fat diet in both the pre – and post-experimental periods. Eight male normolipidemic subjects participated. In the first experimental period of phase-1, two subjects were randomly assigned to one of four experimental diets: sunflower and olive oil (S/O); canola (CAN); soybean (Soy); and sunflower, olive, and flax (S/O/F). The experimental diets were identical to the pre – and – post experimental diets with the exception that 75% of the fat source was substituted with these oil combinations. For the subsequent experimental periods in phase 1 and 2, each pair of subjects were switched to a different diet in the following predetermined order: CAN to S/O/F; S/O/F to S/O; S/O to Soy, and Soy to Can. The experimental diets contained approximately one half the saturated fat content of the pre – and post experimental diets. Fasting blood samples were obtained on days 1, 7, 25, 43, and 49 of each dietary phase and used for subsequent analysis. Mean total cholesterol (TC), LDL-C, VLDL-C, and triglyceride levels were significantly lower after the experimental diets when compared to the mixed fat diets. No differences in TC or lipoprotein cholesterol values were observed between the experimental diets. Dietary fat source had no effect on HDL-C. Mean TG values were significantly lower following the S/O and S/O/F diets compared to the CAN diet. Finally, mean apo-A1 concentrations were 9% and apo-B concentrations were 19% lower following consumption of the experimental diets compared to the mixed diets. No difference was observed in apo A1 or apo B concentrations among the experimental diets. These data indicate that ALA, OA, and LA are equally effective in lowering TC, LDL-C, and VLDL-C, TG and apo A1 and apo B lipoprotein concentrations. However, the exact mechanism by which these fatty acids affect cholesterol metabolism remains to be elucidated.
