Flaxseed oil: acute and chronic supplementation increases serum and tissue concentrations of omega fatty acids in rats

We studied the bioavailability of acute supplementation of scalar doses of flaxseed oil by analysing the level of Linolenic acid (ALA, -3) and Linoleic acid (-6) in serum and tissues (adipose, liver and brain) of rats tested at 2-4-8-16 h after the administration. The amount of flaxseed oil administered by oral rate was 1.9, 4.7, 9.5 mL/kg corresponding to 1, 2.5, 5 g ALA/kg. Two techniques of lipid extraction were investigated to achieve maximal free fatty acids recovery in a reasonably short time. The corresponding fatty acid methyl esters obtained with direct methylation with MeOH/HCl, were quantified by gas chromatography/mass spectrometry (GC/MS) technique. GC-MS analyses were performed on a Gas-Chromatograph Varian 3400 on a HP-INNOWAX column (30 m x 0.25 mm; 0.25 m film thickness). Mass spectra were acquired on a Finnigan MAT SSQ 710A mass spectrometer in the electron impact (EI) mode.Serum ALA levels at 1 g/kg after 2h in the flaxseed oil group increased by 70% from 0.067 ± 0.007 to 0.096 ± 0.008 mg/mL (P<0.001 Anova) whereas no significant increase occurred in the flaxseed oil group at 2.5 g/kg (0.142 ± 0.009) or at 5 g/kg after 2 h (0.140 ± 0.008) when compared with the value obtained after 1 g/kg. A statistically significant increase of ALA was found in adipose tissue and in liver 4 h after the administration of 1 g/kg of ALA whereas higher doses (2.5-5 g/kg) did not produce any significant changes. Concerning linoleic acid (-6) no significant increased concentrations were found in serum at the three doses studied confirming that flaxseed oil is mainly a source of -3 fatty acids.