Effects of fish oil alone and combined with long chain (n-6) fatty acids on some coronary risk factors in male subjects

The effects of fish oil alone were compared with those of fish oil combined 1:1 with evening primrose oil rich long chain (n-6) fatty acids in a double-blind cross-over study. After administration of fish oil there was a highly significant increase in 20:5 (n-3) (eicosapentaenoic acid) and 22:6 (n-3) (docosahexaenoic acid) and a significant decrease in (n-6) fatty acids in plasma phospholipids. After consumption of the fish oil/ evening primrose oil mixture, the increase in (n-3) and the decrease in (n-6) fatty acids were considerably smaller. Triglycerides in serum decreased by 36% (P< 0.01) after the fish oil and by 29% (P< 0.05) after fish oil/evening primrose oil mixture. Atherogenic indexed decreased by 12% (P < 0.05) after the fish oil/evening primrose oil and by 6% (P = ns) after fish oil alone. This difference was statistically significant (P < 0.05). Plasma homocysteine was reduced by 10% (P< 0.05) after the fish oil/evening primrose oil mixture and decreased 4% (P = ns) after the fish oil alone. Plasma fibrinogen decreased after both oils. The combined oils did not raise plasminogen activator inhibitor-1 (PAI-1) antigen at all, whereas after fish oil there was a 49% (P < 0.05) increase. Fish oil increased the ratio C20:4 to C20:3, an index of delta-5-desaturase, by 96% (P < 0.001) and reduced the ratio of C20:3 to C18:2, an index of delta-6-desaturase, by 38% (P < 0.001), whereas the fish oil/ evening primrose oil mixture left these indexes unchanged. A high index of delta-5-desaturase has been found to be correlated to increase insulin sensitivity. In conclusion, combination of fish oil and evening primrose oil had more favorable effect on the atherogenic index and caused no increase in PAI-1 antigen. The effects on triglycerides and PAI-1 of the fish oil and the mixture appears to be a result of their (n-3) fatty acid content.