Decreasing Linoleic Acid with Constant α-Linolenic Acid in Dietary Fats Increases (n-3) Eicosapentaenoic Acid in Plasma Phospholipids in Healthy Men1

Abstract

High linoleic acid (LA) intakes have been suggested to reduce α-linolenic acid [ALA, 18:3(n-3)] metabolism to eicosapentaenoic acid [EPA, 20:5(n-3)] and docosahexaenoic acid [DHA, 22:6(n-3)], and favor high arachidonic acid [ARA, 20:4(n-6)]. We used a randomized cross-over study with men (n = 22) to compare the effect of replacing vegetable oils high in LA with oils low in LA in foods, while maintaining constant ALA, for 4 wk each, on plasma (n-3) fatty acids. Nonvegetable sources of fat, except fish and seafoods, were unrestricted. We determined plasma phospholipid fatty acids at wk 0, 2, 4, 6, and 8, and triglycerides, cholesterol, serum CRP, and IL-6, and platelet aggregation at wk 0, 4, and 8. LA and ALA intakes were 3.8 ± 0.12% and 1.0 ± 0.05%, and 10.5 ± 0.53% and 1.1 ± 0.06% energy with LA:ALA ratios of 4:0 and 10:1 during the low and high LA diets, respectively. The plasma phospholipid LA was higher and EPA was lower during the high than during the low LA diet period (P < 0.001), but DHA declined over the 8-wk period (r = −0.425, P < 0.001). The plasma phospholipid ARA:EPA ratios were (mean ± SEM) 20.7 ± 1.52 and 12.9 ± 1.01 after 4 wk consuming the high or low LA diets, respectively (P < 0.001); LA was inversely associated with EPA (r = −0.729, P < 0.001) but positively associated with ARA:EPA (r = 0.432, P < 0.001). LA intake did not influence ALA, ARA, DPA, DHA, or total, LDL or HDL cholesterol, CRP or IL-6, or platelet aggregation. In conclusion, high LA intakes decrease plasma phospholipid EPA and increase the ARA:EPA ratio, but do not favor higher ARA.