Dietary a-Linolenic Acid Alters Tissue Fatty Acid Composition, But Not Blood Lipids, Lipoproteins or Coagulation Status in Humans.
Dietary a-Linolenic Acid Alters Tissue Fatty Acid Composition, But Not Blood Lipids, Lipoproteins or Coagulation Status in Humans.
Year: 1993
Authors: D S Kelley, G J Nelson, J E Love, L B Branch, P C Taylor, P C Schmidt, B E Mackey, J M Iacono.
Publication Name: Lipids.
Publication Details: Volume 28; Number 6; Page 533.
Abstract:
Previous studies in humans have shown that dietary ALA from flaxseed oil can be converted into EPA in the body. Additionally, ALA has been found to reduce platelet aggregation and increase bleeding time in healthy subjects. In this study, the effect of ALA in flaxseed oil on serum lipids and coagulation parameters, and on the fatty acid composition of serum and peripheral blood mononuclear cell (PBMNC) lipids was assessed in ten healthy men (age 21-37 years). Subjects consumed a metabolically controlled diet for 126 days. A stabilization period of 14 days preceded the experimental diets. During this phase all 10 subjects consumed a basal diet (BD) containing 23.4 % of energy (en%) as fat. The experimental diets were fed over two intervention periods of 56 days each. During the first intervention period, 5 subjects consumed the BD containing 23.4 en% fat, and 5 subjects consumed a flaxseed oil supplemented diet containing 28.8 en% fat. The ALA content of the flaxseed oil diet represented 6.3% of calories. Diets were fed in a cross over design between the two groups during the second intervention period. Feeding the flaxseed oil diet did not significantly alter serum TG, TC, HDL-C, LDL-C, VLDL, apoA-I and apoB when compared to the corresponding values in the subjects fed the BD. These results differ from previous research in which n-3 PUFAs from flaxseed oil (ALA) and fish oils (EPA and DHA) lowered serum TG and VLDL, and in some studies, also lowered TC. The authors indicated that the characteristics of the subjects may have been responsible for the lack of effects noted. The volunteers in this study consisted of young active soldiers whose baseline serum lipid levels were lower than those of the average individual. In addition, the BD used contained very low levels of SFA (7 en%) and total fat (23 en%). The investigators speculated that it may not have been feasible to lower serum lipids with the flaxseed oil diet or with fish oils when switching from the type of low SFA and low fat used as the BD. Even though the flaxseed oil diet contained 6 en% of fat higher than the BD, no increases in serum lipid levels were found. From the design of the study, it is not possible to ascertain whether a flaxseed oil diet would have hypolipidemic effects in populations with average or above average serum lipid values. The authors noted that the diets and subjects were chosen for an initial study aimed at determining the effects of ALA in flaxseed oil on immune responses which were suppressed. The flaxseed oil diet did not affect bleeding time, prothrombin time and partial prothrombin time for the subjects. The authors speculated that the lack of effect of the flaxseed oil diet on indices of coagulation may have been due to the reasons cited for serum lipid effects. Feeding the flaxseed oil diet cause a significant increase in ALA concentration in serum and PBMNC lipids. The flaxseed oil diet also caused a significant increase in the EPA and DPA content of PBMNC lipids, and a significant decrease in LA and eicosatrienoic acid contents of serum lipids. The investigators concluded that the effects of dietary ALA on serum lipids, coagulation parameters and on the fatty acid composition of serum and PBMNC lipids should be examined in further studies on individuals consuming higher fat diets more representative of a traditional Western style diet. In addition, subjects with average and higher than average serum lipid levels should be studied.
