Journal Title (Medline/Pubmed accepted abbreviation): Br J Nutr
Page numbers: 1129-1138
Summary of Background and Research Design
Background:There is ongoing debate whether supplementation with antioxidants is beneficial in terms of preventing or minimizing oxidative stress and damage in response to strenuous exercise, or whether it is detrimental by interfering with favorable ph ysiologic effects of exercise training. Studies that have examined high-dosed antioxidant supplementation in long-distance triathletes and ultra-marathon participants have been controversial, showing either beneficial or adverse (ie, pro-oxidant) effects or no effects on the changes in oxidative stress markers. However, antioxidant requirements and possible interactions between endogenous antioxidant defenses and nutritive antioxidants have not been examined in endurance and ultra-endurance athletes.
Hypothesis/purpose of study:To investigate the changes of endogenous and exogenous antioxidants in response to an Ironman triathlon; to note the relevance of antioxidant responses to the indices of oxidative damaged blood lipids, blood cell compounds, and lymphocyte DNA; and to examine whether potential time-points of increased susceptibility to oxidative damage are associated with alterations in the antioxidant status
Subjects:Forty-two nonprofessional, well-trained, male triathletes, who participated in the 2006 Ironman Austria (mean ± standard deviation: age 35.3 ± 7.0 years, weight 75.1 ± 6.4 kg, height 180.6 ± 5.6 cm, body-mass index 23.0 ± 1.2 kg/m2) completed the study and were included in statistical analysis.
Experimental design: Nonrandomized, noncontrolled, prospective study
Treatments and protocol:The subjects did not take any medication from 6 weeks before the race until the end of the study. As an inclusion criterion for participating in the study, they were instructed to avoid antioxidant supplementation at doses more than 100% of recommended daily allowance throughout this period (except during the race). During the race, the dietary intake (including antioxidant-fortified beverages and food) was ad libitum, but the quantities of the intake of nutrients were recorded via a 24-hour dietary recall. The race consisted of 3.8 km swimming, 180 km cycling and 42.2 km running. Blood samples were collected 2 days pre-race, immediately post-race (within 20 minutes), and 1, 5 and 19 days post-race to assess the intake of antioxidant vitamins, oxidative stress markers, and antioxidant status. Total plasma antioxidant capacity were assessed by Trolox-equivalent antioxidant capacity (TEAC), ferric-reducing ability of plasma (FRAP), and oxygen radical absorbance capacity (ORAC) assays.
Summary of research findings:
- The average intakes of vitamin C, α-tocopherol, and ß-carotene were 393 ± 219 mg, 113 ± 59 mg, and 9.1 ±17.9 mg during the race, and 244 ± 248 mg, 10.1 ± 5.7 mg, and 2.7 ± 2.3 mg within the first 24 hours after the race, respectively.
- Immediately post-race, there were significant increases in plasma vitamin C and α-tocopherol (54% and 18%, respectively; P < .01).
- One day post-race, vitamin C concentrations decreased to values that were similar to the pre-race values, whereas other antioxidant nutrient concentrations dropped significantly to below the pre-race concentrations: γ-tocopherol (-25%; P < .01), lutein/zeaxanthin (-15%; P < .05), cryptoxanthin (-8%; P < .05), and ß-carotene (-15%; P < .01).
- Plasma levels of uric acid significantly (P < .001) increased immediately after the triathlon (49%). Subsequently, the uric acid concentrations gradually declined, but remained significantly (P < .001) elevated at all the time-points (P < .001 for 19 days post-race) vs the pre-race values.
- Plasma total bilirubin was significantly (P < .001) higher immediately after the race (39%) than pre-race, increased further 1 day post-race (65%), and significantly (P < .001) declined below the pre-race concentrations 5 days post-race.
- Plasma total protein increased immediately after the race (4%; P < .01); thereafter, there was a significant decrease to below the pre-race values.
- TEAC, FRAP, and ORAC assay values increased significantly (P < .001) immediately after the race (48%, 35%, and 18 %, respectively). The values of all the assays remained significantly higher than the pre-race values until 1 day after the race (25%, 24%, and 11%, respectively; P < .001 for TEAC and FRAP, and P < .05 for ORAC).
- All oxidative stress markers significantly increased in response to the race.
- A significant decrease of DNA strand breaks in lymphocytes was observed immediately after the race.
- One day post-race, DNA migration due to strand breaks increased (P < .01), then returned to the pre-race levels 5 days post-race, then decreased further to below the initial levels 19 days post-race (P < .01).
- No associations were observed between oxidative stress markers, total antioxidant capacity, and endpoints of DNA damage based on percentile distribution by the plasma concentrations and intakes of vitamin C, α-tocopherol, and ß-carotene.
Interpretation of findings/Key practice applications:
The present data are part of a larger ongoing study that aimed to get a broader picture of exercise-induced skeletal muscle damage, inflammatory and immunologic alterations, myocardial stress, oxidative stress, genome stability, and the relationship of DNA damage with inflammatory responses in a large cohort of participants of an Ironman triathlon. In general, training- and acute exercise-induced adaptations in protective mechanisms, including endogenous antioxidant defenses, counteracted severe oxidative damage of blood lipids, blood cell compounds, and DNA in circulating lymphocytes in response to an ultra-endurance exercise. Importantly, the increase in the total plasma antioxidant capacity played a major role, and a protective effect was apparent with regard to DNA stability. Significant decreases in carotenoids and tocopherol 1 day post-race indicate that monitoring antioxidant intake during the first 24 hours of recovery following an acute ultra-endurance exercise is necessary. Neither clear beneficial nor detrimental effects of higher antioxidant intakes in the peri-exercise period were observed. However, this study was not a controlled study and did not specifically evaluate the effects of antioxidant supplements on oxidative stress parameters.