Vitamin E supplementation counteracts the fish oil-induced increase of blood glucose in humans

Abstract

The objective of the study was to examine the effect of extra vitamin E in fish oil on some variables of glucose and lipid metabolism and on fibrinolysis in mildly hypertriglyceridemic men. Twelve subjects were given 30 mL/d of an ordinary fish oil (5.4 g eicosapentaenoic acid and 3.2 g docosahexaenoic acid) stabilized with vitamin E (1.5 IU/g, FO) and the same fish oil supplemented with extra vitamin E (4.5 IU/g, FO+E) for 4 wk in a randomized double-blind cross-over study. Fasting blood glucose concentration was increased after the period on FO (by 10%, P < 0.05), but was not changed after FO+E. Serum insulin was not significantly changed after the period on FO, but it tended to increase after FO+E. Fasting insulin/glucose ratio was not changed after FO, but was significantly increased after FO+E (P < 0.05), indicating a more adequate pancreatic insulin response to glucose after FO+E. Serum triglycerides decreased during the period on FO and FO+E (by 43%, P < 0.001, and 41%, P < 0.001, respectively) and plasma lipoprotein (a) [Lp(a)] concentrations in five individuals with high Lp(a) levels (>270 mg/L) also decreased (by 22%, P < 0.05, and 16%, NS, respectively), with no significant differences between treatments. Plasminogen activator inhibitor-1 activity and antigen were significantly increased after both treatments. It is concluded that extra vitamin E counteracts the blood glucose increase that is often seen after fish oil intake.