Encapsulated fish oil enriched in alpha-tocopherol alters plasma phospholipid and mononuclear cell fatty acid compositions but not mononuclear cell functions

Background Several studies have reported that dietary fish oil (FO) supplem entation alters cytokine production and other functional activities of peri pheral blood mononuclear cells (PBMC). However, few of these studies have b een placebo controlled and few have related the functional changes to alter ations in PBMC fatty acid composition Patients and methods Healthy subjects supplemented their diets with 9 g day (-1) of encapsulated placebo oil (3:1 mix of coconut and soybean oils), oli ve oil (OO), safflower oil (SO), evening primrose oil (EPO) or FO [providin g 2.1 g eicosapentaenoic acid (EPA) plus 1.1 g docosahexaenoic acid (DHA) p er day] for 12 weeks; the capsules also provided 205 mg alpha-tocopherol pe r day. Blood was sampled at 4-weekly intervals and plasma and PBMC prepared . Plasma phospholipid and PBMC fatty acid composition, plasma alpha-tocophe rol and thiobarbituric acid-reactive substance concentrations, plasma total antioxidant capacity, the proportions of different PBMC subsets, the propo rtions of PBMC expressing the adhesion molecules CD2, CD11b and CD54, and P BMC functions (lymphocyte proliferation, natural killer cell activity, cyto kine production) were measured. All measurements were repeated after a 'was hout' period of 8 weeks. Results The placebo, OO and SO capsules had no effect on plasma phospholipi d or PBMC fatty acid composition. The proportion of dihomo-gamma-linolenic acid in plasma phospholipids was elevated in subjects taking EPO and was de creased in subjects taking FO. There was no appearance of gamma-linolenic a cid in the plasma phospholipids or PBMC in subjects taking EPO. There was a marked increase in the proportion of EPA in the plasma phospholipids (10-f old) and PBMC (four-fold) of subjects taking FO supplements; this increase was maximal after 4 weeks of supplementation. There was an increase in the proportion of DHA in plasma phospholipids and PBMC, and an approximately 20 % decrease in the proportion of arachidonic acid in plasma phospholipids an d PBMC, during FO supplementation. Plasma concentrations of alpha-tocophero l were significantly elevated during supplementation in all subjects and re turned to baseline values after the washout period. There were no effects o f supplementation with any of the capsules on total plasma antioxidant acti vity or plasma thiobarbituric acid-reactive substances or on the proportion of different PBMC subsets, on the proportion of PBMC expressing adhesion m olecules, on natural killer cell activity, on the proliferation of mitogen- stimulated. whole blood cultures or PBMC, or on the ex: vivo production of a range of cytokines by whole blood cultures or PBMC cultures stimulated by either concanavalin A or lipopolysaccharide. Conclusion Supplementation of the diet with 3.2 g EPA plus DHA per day mark edly alters plasma phospholipid and PBMC fatty acid compositions. The lack of effect of FO upon PBMC functions may relate to the level of or-tocophero l included in the supplements.