Dietary flaxseed oil and high‐oleic canola oil modulate plasma fatty acid composition and conversion of 13C‐α‐linolenic acid to long‐chain fatty acids

Abstract

The objective was to analyze the effects of diets enriched in flaxseed oil (FXCO) or high-oleic canola oil (HOCO) versus a Western fat (WF) blend on plasma fatty acid composition and conversion of 13C-α-linolenic acid (ALA) to long-chain n-3 fatty acids. Using a randomized, controlled, crossover trial, 18 hyperlipidemic subjects consumed 3 isoenergetic diets for 28 d enriched in FXCO (20.6 g/d ALA), HOCO (2.4 g/d ALA), or WF (1.3 g/d ALA). On day 27, blood was sampled at t = 0, 24, and 48 h after subjects consumed 45 mg uniformly labelled 13C-ALA. FXCO diet increased plasma ALA ~5-fold (4.69 ± 0.26% total fatty acids; P<0.001), eicosapentaenoic acid (EPA) ~2-fold (1.76 ± 0.17%; P<0.001), and docosapentaenoic acid (DPA) by ~50% (0.76 ± 0.04%; P<0.001), with no change in docosahexaenoic acid (DHA) compared to HOCO and WF diets. At 24 h the amount of administered 13C-ALA recovered as plasma 13C-EPA and 13C-DPA was 0.86 ± 0.10 mg and 0.13 ± 0.02 mg after FXCO diet, which was lower (P=0.004 and P=0.011) than that of 1.33 ± 0.22 mg and 0.23 ± 0.04 mg after HOCO diet and 1.15 ± 0.16 mg and 0.24 ± 0.05 mg after WF diet, respectively. No change in 13C-DHA was observed between diets. In conclusion, although a high intake of ALA in FXCO diet increased plasma levels of n-3 fatty acids, such increased levels are not a result of higher conversion efficiency, particularly for DHA. Supported by Flax Canada 2015, Canola Council of Canada, and ARDI. Grant Funding Source: Flax Canada 2015, Canola Council of Canada, and ARDI