Dietary α-Linolenic Acid, EPA, and DHA Have Differential Effects on LDL Fatty Acid Composition but Similar Effects on Serum Lipid Profiles in Normolipidemic Humans

Abstract

Our aim was to study the effects of increased dietary intake of alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), or docosahexaenoic acid (DHA) on serum lipids and LDL fatty acid compositions. To this end, a controlled parallel study was conducted in 74 healthy normolipidemic men and women aged 19-43 y. Participants were randomly assigned to 1 of 3 interventions and consumed a total intake of 4.4 g/d ALA (ALA group), 2.2 g/d EPA (EPA group), and 2.3 g/d DHA (DHA group) for 6 wk. Fatty acid ethyl esters were incorporated into margarines, which replaced the participant's normal spread. The ALA, EPA, or DHA intake led to a significant enrichment of the LDL with the respective (n-3) fatty acid. In addition, LDL EPA contents in the ALA group increased by 36% (P < 0.05) with no changes in LDL DHA. The EPA intervention led to an additional enrichment with DHA (24%; P < 0.001), whereas the DHA intervention further increased the amount of EPA (249%; P < 0.001). ALA, EPA, or DHA intake did not affect fasting serum concentrations of total and LDL cholesterol, but fasting serum triacylglycerol concentrations significantly decreased in the EPA (-0.14 mmol/L) and DHA (-0.30 mmol/L) interventions and also in the ALA intervention (-0.17 mmol/L). DHA intake significantly increased serum HDL cholesterol, whereas no changes were found with ALA or EPA intake. In conclusion, the present data support the hypothesis that isolated dietary ALA, EPA, and DHA intakes lead to differential enrichment in LDL due to interconversion. Moderate amounts of ALA, EPA, and DHA are effective in improving lipid profiles of normolipidemic humans.

Metabolism and functional effects of plant-derived omega-3 fatty acids in humans

“…The subjects consumed margarines providing either 4.4 g of ALA, or 2.2 g of EPA or 2.3 g of DHA ethyl ester daily for 6 weeks. The study confirmed the TAG lowering effect of EPA (15% lower) and DHA (30% lower) and reported a 15% reduction in fasting serum TAG in the ALA group [140]. Patenaude et al compared the effect of increased consumption of ALA, from flaxseed oil (6 g/d for 4 weeks), in two age groups and reported a 20% decrease in circulating TAG concentration in younger subjects (18-29 y) compared to a 3.5% increase in older subjects (45-69 y) [144].…”

“…The reported effects of ALA on fasting TAG concentrations are also inconsistent; although a number of studies report a decrease [107,134,140,144,146,160,233,243,244], the majority (31 out of 40) report no effect (Table 9). There is consistent evidence that EPA and DHA lower blood TAG concentrations [186,246,247].…”

“…There is consistent evidence that EPA and DHA lower blood TAG concentrations [186,246,247]. Egert et al evaluated the effects of increased dietary intake of ALA, EPA and DHA on serum TAG in normolipidemic non-obese subjects [140]. The subjects consumed margarines providing either 4.4 g of ALA, or 2.2 g of EPA or 2.3 g of DHA ethyl ester daily for 6 weeks.…”

Nutritional Management of Disturbances in Lipoprotein Concentrations

“…The hypotriglyceridaemic effect of long chain n-3 PUFAs, mediated by several mechanisms such as enhanced hepatic fatty acid oxidation [69], inhibition of fatty acid and triglyceride synthesis, reduced assembly and secretion of VLDL triglyceride concentrations [70], facilitates triglyceride rich lipoprotein removal through enhanced LPL activity in plasma [71]. Significant increases in HDL have been observed after DHA supplementation [67,68,72,73]; it may be related to decreased cholesteryl ester transfer protein activity that reduces the exchange from HDL cholesterol ester and VLDL, resulting in larger, more cholesterol-rich HDL cholesterol particles [74,75].…”

“…Compares EPA and DHA, EPA-ethyl ester shows no change in triglyceride concentrations, suggesting that DHA is the active agent in fish oil, that decreases triglyceride concentrations. Therefore among long chain n-3 PUFAs, EPA may produce favourable effects on triglyceride and HDL cholesterol concentrations [67,68]. The hypotriglyceridaemic effect of long chain n-3 PUFAs, mediated by several mechanisms such as enhanced hepatic fatty acid oxidation [69], inhibition of fatty acid and triglyceride synthesis, reduced assembly and secretion of VLDL triglyceride concentrations [70], facilitates triglyceride rich lipoprotein removal through enhanced LPL activity in plasma [71].…”