Thirty-four healthy non-smoking subjects (20 men and 14 women) were given 25 ml cod liver oil (CLO) daily as dietary supplement for 8 weeks in a controlled cross-over study.

Prior to intervention, women had significantly higher serum total (P < 0.05) and high density lipoprotein (HDL) (P < 0.001) cholesterol values, higher platelet counts (P < 0.05) and lower thromboxane B2 (TxB2) generation (P < 0.01) in response to collagen stimulation in platelet-rich plasma (PRP) than men. Before intervention, no gender differences in platelet aggregation were observed.

Following CLO intervention, serum triglycerides were reduced by 0.21 +/- 0.09 mmol/l (P < 0.05) in men. LDL cholesterol increased in men by 0.28 +/- 0.12 mmol/l (P < 0.05), while the values in women decreased insignificantly. The response in LDL cholesterol to CLO supplementation differed significantly between genders (P < 0.05). HDL cholesterol was not altered in any group. Mean platelet volume (MPV) increased by approximately 6% in both sexes (P < 0.01).

After CLO intake, platelet sensitivity to collagen in PRP decreased in men only (P < 0.01), and the response was significantly different from that in women (P < 0.05). Thromboxane B2 generation following platelet aggregation in PRP was equally decreased by CLO.

Our findings indicate sex differences in the response to CLO regarding LDL cholesterol and platelet sensitivity to collagen in PRP.