Cetoleic acid rich fish oil increases plasma levels of eicosapentaenoic and docosapentaenoic acids in healthy volunteers: a double-blinded, randomised, controlled trial

Intake of fish and supplementation with n-3 polyunsaturated fatty acids (PUFA) are associated with reduced incidence of cardiovascular disease (CVD). Cetoleic acid promotes n-3 PUFA generation in salmon and human HepG2 cells, but data in humans are scarce. To explore the effect of cetoleic acid on n-3 PUFA levels, we performed a double-blinded randomised controlled trial in healthy adults (37 females and 12 males) for four weeks. The participants were randomised to consume either capsules with mackerel oil, naturally rich in cetoleic acid, or a control oil, both with a similar concentration of n-3 PUFA. Clinicaltrials.gov (NCT04841044). Supplements with mackerel oil resulted in higher plasma levels of the n-3 PUFAs 20:4n-3 (Eicosatetraenoic acid) and 20:5n-3 (Eicosapentaenoic acid) as compared with those receiving control oil. In addition, those who received the cetoleic-rich capsules had higher levels of 20:4n-3 in the RBC membrane and a decrease in expression of elongation of very long chain fatty acids protein 5 in peripheral blood mononuclear cells. We found no differences in lipid, glucose or C-reactive protein between the two treatment groups, consisting of healthy subjects. Our data suggests that supplementation with cetoleic-rich mackerel oil may result in increased levels of certain n-3 PUFAs. Further studies should include patients with or at risk for metabolic and CVD.