The effect of dietary fish oil supplement upon the content of dihomo-gammalinolenic acid in human plasma phospholipids

Patients (n = 23) with definite or classical rheumatoid arthritis were given 18 g/day fish oil in gelatin capsules which provided 3.2 g/day EPA and 2.0 g/day DHA. The treatment period was 12 weeks followed by a 4 week washout period. Fish oil supplementation to the diet resulted in a substantial increase in the content of EPA and DHA in each of the plasma fractions examined (PL, TG, and CE). Little change was seen in the AA level of the TG and CE fractions but a modest decrease in AA was seen in PL. However the intake of fish oil caused a significant depression in the content of DGLA in the PL (p<0.005) and CE (p<0.01) fractions relative to baseline values. All changes had reverted to near baseline levels 4 weeks after dietary intervention. Since DGLA is the precursor of PGE₁, which has been shown to be anti-inflammatory, our findings suggest that the anti-inflammatory effects of fish oil consumption could be mitigated by an associated reduction in DGLA.