The dietary alpha-linolenic acid to linoleic acid ratio does not affect the serum lipoprotein profile in humans
The dietary alpha-linolenic acid to linoleic acid ratio does not affect the serum lipoprotein profile in humans
Year: 2005
Authors: Goyens, PL, Mensink, RP.
Publication Name: J. Nutr.
Publication Details: Volume 135, Page 2799.
Abstract:
To date, the effects of dietary ALA, LA, and the ALA:LA ratio on lipoprotein particle sizes and subclass distributions has not been investigated in detail. The objective of the present study was to compare the effects of ALA, LA, and the ALA:LA ratio on fasting serum lipids and apolipoproteins concentrations, and on lipoprotein particle subclasses, in humans. Fifty-four healthy men and women aged 18-54 years participated in this 10-week randomized, double-blinded, parallel intervention study. All participants consumed a run in diet for the first four weeks that reflected the average daily intake of the Dutch population, providing 7% of energy as LA and 0.4% as ALA. For the remaining 6-weeks, participants were randomly allocated into one of three experimental diet groups: 1) Control group (n=18) – subjects continued to consume the same diet as for the run-in period (7% of energy as LA; 0.4% as ALA; ratio of ALA:LA of 1.19); 2) Low LA group (n=18) – 3% of energy was consumed as LA and 0.4% of energy was consumed as ALA; 3) High ALA group (n=18) – 7% energy was consumed as LA and 1.1% of energy consumed as ALA. The ratio of ALA:LA was 1.19 for the control diet and 1:7 for the other two diets. All three diets supplied 15% energy as protein, 35% as fat, and 50% as carbohydrates. The experimental dietary fats supplying the ALA and LA were provided in the form of a margarine, which in turn was also used to prepare bakery items. The source of ALA was primarily canola oil, while monounsaturated fat and LA was provided primarily via olive and sunflower oils, respectively. Fasting blood samples were obtained at baseline, at the end of the run in period, and at the end of the 6-week experimental period for subsequent analysis of serum lipids, apoliproteins, and lipoproteins. The results showed a slight reduction in LDL-cholesterol, total-cholesterol, apolipoprotein (apo B), and total:HDL cholesterol ratio following the ALA diet compared to the control group. HDL-cholesterol, apo-A-1, or triacylglycerol concentrations were not affected by any of the dietary interventions. Decreases in total VLDL particle concentrations were observed for both the low LA and high ALA groups. These reductions were the probable result of a decrease in medium VLDL (-16 nmol/L) and small VLDL (-14 nmol/L) in the low LA and high ALA group, respectively. Finally, changes in HDL particle size distributions and VLDL, LDL, and HDL mean particle sizes did not differ among the 3 groups. In conclusion, the dietary ALA:LA ratio does not appear to be a determinant of serum lipid and lipoprotein concentrations. Furthermore, a small increase in ALA intake resulted in a significant decrease in LDL-cholesterol and apo-B concentrations. It is believed that this decrease is a result of a decrease in small VLDL particles – the precursor to LDL lipoproteins; however, further research is necessary to confirm these findings.
