Effect of n-3 fatty acids and antioxidants on oxidative stress after exercise
Journal Title (Medline/Pubmed accepted abbreviation): Med Sci Sports Exerc
Page numbers: 1704-1711
Summary of Background and Research Design
Background: n-3 fatty acids are known to have anti-inflammatory activity that may reduce oxidative stress. Supplementation with antioxidant vitamins has been proposed to counteract oxidative stress and improve antioxidant status. This study investigated the effects of daily supplementation with vitamins and n-3 fatty acids over 6 weeks and during 3 days of continuous exercise and on plasma F2-isoprostanes (marker of lipid peroxidation), plasma n-3 fatty acids, and other antioxidant status markers in the blood (oxygen radical absorption capacity [ORAC], ferric reducing antioxidant potential [FRAP])
Hypothesis: The authors hypothesized that n-3 fatty acids and antioxidant vitamins would reduce oxidative stress (ie, decrease F2-isoprostanes) and enhance antioxidant status (increase ORAC and FRAP).
Subjects: Forty-eight trained cyclists (mean age 27 to 22 yr, mean maximal oxygen consumption [VO2max] 59 to 67 mL/kg/min, mean power 251 to 309 W, and training 209 to 264 km/wk or 0.6 to 1.1 hours/day) participated in the study.
Experimental design: Randomized, double-blind, parallel-group study
Treatments and protocol:Cyclists were randomized to 1 of 4 cohorts: n-3 fatty acids (N3) (n = 11) (2,000 mg of eicosapentaenoic acid [EPA] and 400 mg of docosahexaenoic acid [DHA]), a vitamin-mineral (VM) complex (n = 12) emphasizing vitamins C (2,000 mg), E (800 IU), A (3,000 IU), and selenium (200 μg), a VM and n-3 fatty acid combination (VN3) (n = 13), or placebo (P) (n = 12). Subjects ingested the supplements daily for 6 weeks. Exercise sessions occurred over 3 consecutive days in which subjects cycled for 3 hours at ~57% maximal watts. Metabolic measurements were made every 30 minutes of cycling. Blood was collected at baseline and before and after exercise.
Summary of research findings:
- Administration of N3 alone had no positive effects on FRAP or ORAC and actually increased plasma F2-isoprostanes (P = 0.014) relative to the other 3 treatments. The addition of the VM to N3 ameliorated this effect.
- EHA and DHA plasma values were higher after supplementation (interaction effect P = .001 and .006, respectively) in both n-3 supplemented groups (N3 and VN3).
- ORAC declined similarly among all groups after exercise.
- FRAP exhibited significant interaction (P = .045) and was significantly increased after exercise in the VN3 and VM groups (P < .01).
Interpretation of findings/Key practice applications:
Although N3 are generally understood to protect against oxidative stress (eg, lipid peroxidation), this study shows that loading with N3 alone for a period of 6 weeks before strenuous exercise actually increased levels of F2-isoprostanes in the plasma, a marker of greater lipid peroxidation. The addition of antioxidant VM to fish oil did attenuate this effect and they also helped to increase FRAP in the plasma. In summary, this study shows that the potential benefits of fish oil (eg, increased vasodilation, anti-inflammatory effect) must be weighed against the possibility of adverse effects associated with increased lipid peroxidation. The VM in this study provided some benefits (increased FRAP, negation of fish-oil induced increase in F2-isoprostanes), but could not reverse the decline in ORAC caused by exercise. It is not clear what physiologic significance the changes in these biomarkers in this study might carry regarding exercise performance and recovery, so more research is needed.