Antioxidant supplementation preserves antioxidant response in physical training and low antioxidant intake

Trimethylamine N-Oxide Improves Exercise Performance by Reducing Oxidative Stress through Activation of the Nrf2 Signaling Pathway

Trimethylamine N-oxide (TMAO) has attracted interest because of its association with cardiovascular disease and diabetes, and evidence for the beneficial effects of TMAO is accumulating. This study investigates the role of TMAO in improving exercise performance and elucidates the underlying molecular mechanisms. Using C2C12 cells, we established an oxidative stress model and administered TMAO treatment. Our results indicate that TMAO significantly protects myoblasts from oxidative stress-induced damage by increasing the expression of Nrf2, heme oxygenase-1 (HO-1), NAD(P)H dehydrogenase (NQO1), and catalase (CAT). In particular, suppression of Nrf2 resulted in a loss of the protective effects of TMAO and a significant decrease in the expression levels of Nrf2, HO-1, and NQO1. In addition, we evaluated the effects of TMAO in an exhaustive swimming test in mice. TMAO treatment significantly prolonged swimming endurance, increased glutathione and taurine levels, enhanced glutathione peroxidase activity, and increased the expression of Nrf2 and its downstream antioxidant genes, including HO-1, NQO1, and CAT, in skeletal muscle. These findings underscore the potential of TMAO to counteract exercise-induced oxidative stress. This research provides new insights into the ability of TMAO to alleviate exercise-induced oxidative stress via the Nrf2 signaling pathway, providing a valuable framework for the development of sports nutrition supplements aimed at mitigating oxidative stress.

Short-Term Consumption of Hydrogen-Rich Water Enhances Power Performance and Heart Rate Recovery in Dragon Boat Athletes: Evidence from a Pilot Study

(1) Background: Exercise that exceeds the body’s accustomed load can lead to oxidative stress and increased fatigue during intense training or competition, resulting in decreased athletic performance and an increased risk of injury, and the new medicinal H₂ may be beneficial as an antioxidant. Therefore, we explored the effect of short-term supplementation of hydrogen-rich water (HRW) on the work performance and fatigue recovery of dragon boat athletes after training. (2) Methods: Eighteen dragon boat athletes who trained for 4 h a day (2 h in the morning and 2 h in the afternoon) were divided into an HRW group (n = 9) and a placebo water (PW) group (n = 9), drinking HRW or PW for 7 days. Each participant completed 30 s rowing dynamometer tests, monitoring the heart rate at baseline (i.e., Day 1) and after the intervention (on Day 8). (3) Result: Drinking HRW increased the maximum power and average power of the 30 s rowing test and decreased the maximum heart rate during the period. After the rowing test, the HRW group’s heart rate dropped significantly after 2 min of recovery, while the PW group’s heart rate did not drop. There was no significant difference between the 30 s rowing distance and the predicted duration of rowing 500 m. (4) Conclusions: Drinking HRW in the short term can effectively improve the power performance of dragon boat athletes and is conducive to the recovery of the heart rate after exercise, indicating that HRW may be a suitable means of hydration for athletes.

The lack of association between dietary antioxidant quality score with handgrip strength and handgrip endurance amongst Tehranian adults: A cross-sectional study from a Middle East country

OBJECTIVE

The association between dietary antioxidant quality score (DAQS) and handgrip strength (HS) and handgrip endurance (HE) is still unclear. We aimed to investigate whether adherence to dietary antioxidant quality score (DAQS) is associated with handgrip strength (HS) and handgrip endurance (HE) amongst adults in Tehran.

METHODS

This cross-sectional study was conducted on 270 (43.7% males, mean age 37 years and 56.3% females, mean age 35 years) apparently healthy adult subjects (53.2% were married) selected from different parts of Tehran, Iran. Dietary intake was assessed using a 168-item validated food frequency questionnaire. DAQS was calculated using antioxidant-nutrient intake. Body composition was measured using a body composition analyser. Handgrip strength and endurance were measured by a digital handgrip dynamometer. Relative muscle strength was expressed as the ratio of handgrip strength by body mass index (BMI).

RESULTS

The results showed that DAQs had no significant association with HS (P = .67, adjusted R²  = .60) and HE (P = .19, adjusted R²  = .08) after adjusting for potential confounders. However, a significant positive association was found between selenium intake and HE even after adjusting for potential confounders (P = .01, adjusted R²  = .10). After controlling for potential confounders no differences in the mean of HS (P = .29) and also HE (P = .61) amongst tertiles of DAQS was found. Positive linear association was found between vitamin C (P = .02, adjusted R²  = .53) and vitamin E (P = .03, adjusted R²  = .55) intake with relative muscle strength.

CONCLUSION

Our results revealed that no significant association between DAQS and HE and HS. It was found that more intake of selenium was positively linked to HE. Dietary intake of vitamin C and vitamin E are associated with higher relative muscle strength. It is evident that more prospective studies are needed to confirm the veracity of our results.

Dietary Adjustments to Altitude Training in Elite Endurance Athletes; Impact of a Randomized Clinical Trial With Antioxidant-Rich Foods

Background: Altitude training stresses several physiological and metabolic processes and alters the dietary needs of the athletes. International Olympic Committee (IOC)'s Nutrition Expert Group suggests that athletes should increase intake of energy, carbohydrate, iron, fluid, and antioxidant-rich foods while training at altitude. Objective: We investigated whether athletes adjust their dietary intake according to the IOC's altitude-specific dietary recommendations, and whether an in-between meal intervention with antioxidant-rich foods altered the athletes' dietary composition and nutrition-related blood parameters (mineral, vitamin, carotenoid, and hormone concentrations). Design: The dietary adjustments to altitude training (3 weeks at 2,320 m) were determined for 31 elite endurance athletes (23 ± 5 years, 23 males, 8 females) by six interviewer-administered 24-h dietary recalls on non-consecutive days; three before and during the altitude camp. The additional effect of in -between meal intervention with eucaloric antioxidant-rich or control snacks (1,000 kcal/day) was tested in a randomized controlled trial with parallel design. Results: At altitude the athletes increased their energy intake by 35% (1,430 ± 630 kcal/day, p < 0.001), the provided snacks accounting for 70% of this increase. Carbohydrate intake increased from 6.5 ± 1.8 g/kg body weight (BW) (50 E%) to 9.3 ± 2.1 g/kg BW (53 E%) (p < 0.001), with no difference between the antioxidant and control group. Dietary iron, fluid, and antioxidant-rich food intake increased by 37, 38, and 104%, respectively, in the whole cohort. The intervention group had larger increases in polyunsaturated fatty acids (PUFA), ω3 PUFA (n-3 fatty acids), ω6 PUFA (n-6 fatty acids), fiber, vitamin C, folic acid, and copper intake, while protein intake increased more among the controls, reflecting the nutritional content of the snacks. Changes in the measured blood minerals, vitamins, and hormones were not differentially affected by the intervention except for the carotenoid; zeaxanthin, which increased more in the intervention group (p < 0.001). Conclusions: Experienced elite endurance athletes increased their daily energy, carbohydrate, iron, fluid, and antioxidant-rich food intake during a 3-week training camp at moderate altitude meeting most of the altitude-specific dietary recommendations. The intervention with antioxidant-rich snacks improved the composition of the athletes' diets but had minimal impact on the measured nutrition-related blood parameters. Clinical Trial Registry Number: NCT03088891 (www.clinicaltrials.gov), Norwegian registry number: 626539 (https://rekportalen.no/).

Antioxidant Supplementation and Adaptive Response to Training: A Systematic Review

BACKGROUND

Antioxidant supplementation has become a common practice among athletes to theoretically achieve a reduction in oxidative stress, promote recovery and improve performance.

OBJECTIVE

To assess the effect of antioxidant supplements on exercise.

METHODS

A systematic literature search was performed up to January 2019 in MEDLINE via EBSCO and Pubmed, and in Web of Sciences based on the following terms: "antioxidants" [Major] AND "exercise" AND "adaptation"; "antioxidant supplement" AND "(exercise or physical activity)" AND "(adaptation or adjustment)" [MesH]. Thirty-six articles were finally included.

RESULTS

Exhaustive exercise induces an antioxidant response in neutrophils through an increase in antioxidant enzymes, and antioxidant low-level supplementation does not block this adaptive cellular response. Supplementation with antioxidants appears to decrease oxidative damage blocking cell-signaling pathways associated with muscle hypertrophy. However, upregulation of endogenous antioxidant enzymes after resistance training is blocked by exogenous antioxidant supplementation. Supplementation with antioxidants does not affect the performance improvement induced by resistance exercise. The effects of antioxidant supplementation on physical performance and redox status may vary depending on baseline levels.

CONCLUSION

The antioxidant response to exercise has two components: At the time of stress and adaptation through genetic modulation processes in front of persistent pro-oxidant situation. Acute administration of antioxidants immediately before or during an exercise session can have beneficial effects, such as a delay in the onset of fatigue and a reduction in the recovery period. Chronic administration of antioxidant supplements may impair exercise adaptations, and is only beneficial in subjects with low basal levels of antioxidants.

Nutritional strategies for maintaining muscle mass and strength from middle age to later life: A narrative review

Progressive age-related reductions in muscle mass and strength (sarcopenia) can cause substantial morbidity. This narrative review summarizes evidence of nutritional interventions for maintaining muscle mass and strength from midlife through old age. PubMed and Cochrane databases were searched to identify studies of dietary intake and nutritional interventions for sustaining muscle mass and strength. The benefits of progressive resistance training with and without dietary interventions are well documented. Protein and amino acid (particularly leucine) intake should be considered, and supplementation may be warranted for those not meeting recommended intakes. Vitamin D receptors are expressed in muscle tissue; meta-analyses have shown that vitamin D benefits muscle strength. Data suggest that milk and other dairy products containing different bioactive compounds (i.e. protein, leucine) can enhance muscle protein synthesis, particularly when combined with resistance exercise. Omega-3 s can improve muscle mass and strength by mediating cell signaling and inflammation-related oxidative damage; no studies were specifically conducted in sarcopenia. Low-dose antioxidants (e.g. vitamins C and E) can protect muscle tissue from oxidative damage, but relevant studies are limited. Magnesium is involved with muscle contraction processes, and data have shown benefits to muscle strength. Acidogenic diets increase muscle protein breakdown, which is exacerbated by aging. Alkalizing compounds (e.g. bicarbonates) can promote muscle strength. Small studies of probiotics and plant extracts have generated interest, but few large studies have been conducted. Based on available data, dietary and supplemental interventions may add to the benefits of exercise on muscle mass and strength; effects independent of exercise have not been consistently shown.

Changes in Triathletes' Performance and Body Composition During a Specific Training Period for a Half-Ironman Race

The number of recreational athletes completing a Half-Ironman triathlon has increased exponentially in recent years. However, there is a lack of research on how to train for this kind of an event. The purpose of this study was thus to analyse triathletes’ changes in performance and body composition following a triathlon-specific training period. Fourteen male amateur triathletes completed a 7-week period of general training and a 13-week period of specific training for a Half-Ironman triathlon. Anthropometric measures and performance tests were carried out to assess the effects of the specific training program. Results showed that the pre-test value of VO_2max for cycling was inversely correlated not only with the percentage of change in cycling performance, but also with the percentage change in several variables of running performance. In swimming, inverse correlations were observed between the time of the first 800 m test and the time percentage change for this test, but not with the percentage change in the performance of other segments of the race. Moreover, the somatotype component of endomorphy and the fat mass percentage of the first anthropometry were highly correlated with the percentage change in VO_2max in the run segment. These results highlight the importance of providing individualised training, considering that the same training program had a different impact on recreational triathletes belonging to the same group. Amateur athletes with higher initial performance levels probably need a greater amount of training to achieve improved adaptation.

Effects of enzymatically modified isoquercitrin in supplementary protein powder on athlete body composition: a randomized, placebo-controlled, double-blind trial

Background

Enzymatically modified isoquercitrin (EMIQ), a water-soluble quercetin, has been shown to intensify muscle hypertrophy in mice. We investigated the effect of EMIQ in supplementary protein powder on athlete body composition.

Methods

Forty Japanese males who played American football (age: 19.8 ± 1.4 years; body height: 174.1 ± 6.0 cm; body mass: 75.5 ± 10.7 kg) were assigned to a randomized, placebo-controlled, double-blind trial of parallel group. Participants received either EMIQ in whey protein (EW, n = 19) or contrast whey protein (W, n = 20) 6 days per week over 4 months. Body composition was assessed using dual-energy X-ray absorptiometry. Markers of oxidative stress, derivatives of reactive oxygen metabolites (d-ROMs) and biological antioxidant potential (BAP), were assessed using a free radical analytical system. Data were analyzed using a univariate and repeated measures general model statistics.

Results

After 4 months, changes in lower limb fat-free mass and muscle mass were significantly greater in the EW group than in the W group (mean change ±95% CI; W: 324.1 ± 284.3, EW: 950.3 ± 473.2, p = 0.031, W: 255.7 ± 288.6, EW: 930.9 ± 471.5, p = 0.021, respectively). Moreover, the EW group exhibited a significantly higher BAP/d-ROMs ratio, antioxidation index, than the W group after 4 months (mean change ± SD; W: 8.8 ± 1.1, EW: 10.3 ± 2.8; p = 0.028). No significant differences in body mass, lean body mass, fat mass, or lower limb fat mass were observed between the groups.

Conclusion

Ingestion of EMIQ in supplementary protein powder for 4 months exerts antioxidant effects and increases muscle mass among American football players.

Trial registration

University Hospital Medical Information Network Clinical Trial Registry, UMIN000036036. Retrospectively registered in 2019.

Exercise performance and physiological responses: the potential role of redox imbalance

Increases in oxidative stress or decreases in antioxidant capacity, or redox imbalance, are known to alter physiological function and has been suggested to influence performance. To date, no study has sought to manipulate this balance in the same participants and observe the impact on physiological function and performance. Using a single‐blind, placebo‐controlled, and counterbalanced design, this study examined the effects of increasing free radicals, via hyperoxic exposure (F_iO₂ = 1.0), and/or increasing antioxidant capacity, through consuming an antioxidant cocktail (AOC; vitamin‐C, vitamin‐E, α‐lipoic acid), on 5‐kilometer (km) cycling time‐trial performance, and the physiological and fatigue responses in healthy college‐aged males. Hyperoxic exposure prior to the 5 km TT had no effect on performance, fatigue, or the physiological responses to exercise. The AOC significantly reduced average power output (222 ± 11 vs. 214 ± 12 W), increased 5 km time (516 ± 17 vs. 533 ± 18 sec), suppressed ventilation (V_E; 116 ± 5 vs. 109 ± 13 L/min), despite similar oxygen consumption (VO₂; 43.1 ± 0.8 vs. 44.9 ± 0.2 mL/kg per min), decreased V_E/VO₂ (35.9 ± 2.0 vs. 32.3 ± 1.5 L/min), reduced economy (VO₂/W; 0.20 ± 0.01 vs. 0.22 ± 0.01), increased blood lactate (10 ± 0.7 vs. 11 ± 0.7 mmol), and perception of fatigue (RPE; 7.39 ± 0.4 vs. 7.60 ± 0.3) at the end of the TT, as compared to placebo (main effect, placebo vs. AOC, respectively). Our data demonstrate that prior to exercise, ingesting an AOC, but not exposure to hyperoxia, likely disrupts the delicate balance between pro‐ and antioxidant forces, which negatively impacts ventilation, blood lactate, economy, perception of fatigue, and performance (power output and 5 km time) in young healthy males. Thus, caution is warranted in athletes taking excess exogenous antioxidants.

Nutrition and Supplementation in Soccer

Contemporary elite soccer features increased physical demands during match-play, as well as a larger number of matches per season. Now more than ever, aspects related to performance optimization are highly regarded by both players and soccer coaches. Here, nutrition takes a special role as most elite teams try to provide an adequate diet to guarantee maximum performance while ensuring a faster recovery from matches and training exertions. It is currently known that manipulation and periodization of macronutrients, as well as sound hydration practices, have the potential to interfere with training adaptation and recovery. A careful monitoring of micronutrient status is also relevant to prevent undue fatigue and immune impairment secondary to a deficiency status. Furthermore, the sensible use of evidence-based dietary supplements may also play a role in soccer performance optimization. In this sense, several nutritional recommendations have been issued. This detailed and comprehensive review addresses the most relevant and up-to-date nutritional recommendations for elite soccer players, covering from macro and micronutrients to hydration and selected supplements in different contexts (daily requirements, pre, peri and post training/match and competition).

Effect of thyme extract supplementation on lipid peroxidation, antioxidant capacity, PGC-1α content and endurance exercise performance in rats

BACKGROUND

Athletes have a large extent of oxidant agent production. In the current study, we aimed to determine the influence of thyme extract on the endurance exercise performance, mitochondrial biogenesis, and antioxidant status in rats.

METHODS

Twenty male Wistar rats were randomly divided into two groups receiving either normal drinking water (non-supplemented group, n = 10) or thyme extract, 400 mg/kg, (supplemented group, n = 10). Rats in both groups were subjected to endurance treadmill training (27 m/min, 10% grade, 60 min, and 5 days/week for 8 weeks). Finally, to determine the endurance capacity, time to exhaustion treadmill running at 36 m/min speed was assessed. At the end of the endurance capacity test, serum and soleus muscle samples were collected and their superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity, as well as malondialdehyde (MDA) concentration were measured. Protein expression of PGC-1α, as a marker of mitochondrial biogenesis, was also determined in the soleus muscle tissue by immunoblotting assay.

RESULTS

Findings revealed that the exhaustive running time in the treatment group was significantly (p < 0.05) prolonged. Both serum and soleus muscle MDA levels, as an index of lipid peroxidation, had a threefold increase in the thyme extract supplemented group (t18 = 8.11, p < 0.01; t18 = 4.98, p < 0.01 respectively). The activities of SOD and GPx of the soleus muscle were significantly (p < 0.05) higher in the non-supplemented group, while there was no significant difference in serum SOD, GPx activities, and total antioxidant capacity between groups. Furthermore, thyme supplementation significantly (p < 0.05) decreased PGC-1α expression.

CONCLUSIONS

Thyme extract supplementation increased endurance exercise tolerance in intact animals, although decrease of oxidative stress and regulation of the PGC-1α protein expression are not considered as underlying molecular mechanisms.

The effect of mineral-based alkaline water on hydration status and the metabolic response to short-term anaerobic exercise

Previously it was demonstrated that mineralization and alkalization properties of mineral water are important factors influencing acid-base balance and hydration in athletes. The purpose of this study was to investigate the effects of drinking different types of water on urine pH, specific urine gravity, and post-exercise lactate utilization in response to strenuous exercise. Thirty-six male soccer players were divided into three intervention groups, consuming around 4.0 l/day of different types of water for 7 days: HM (n=12; highly mineralized water), LM (n=12; low mineralized water), and CON (n=12; table water). The athletes performed an exercise protocol on two occasions (before and after intervention). The exercise protocol consisted of 5 bouts of intensive 60-s (120% VO_2max) cycling separated by 60 s of passive rest. Body composition, urinalysis and lactate concentration were evaluated – before (t0), immediately after (t1), 5’ (t2), and 30’ (t3) after exercise. Total body water and its active transport (TBW – total body water / ICW – intracellular water / ECW – extracellular water) showed no significant differences in all groups, at both occasions. In the post-hydration state we found a significant decrease of specific urine gravity in HM (1021±4.2 vs 1015±3.8 g/L) and LM (1022±3.1 vs 1008±4.2 g/L). We also found a significant increase of pH and lactate utilization rate in LM. In conclusion, the athletes hydrated with alkaline, low mineralized water demonstrated favourable changes in hydration status in response to high-intensity interval exercise with a significant decrease of specific urine gravity, increased urine pH and more efficient utilization of lactate after supramaximal exercise.

Total Energy Expenditure, Energy Intake, and Body Composition in Endurance Athletes Across the Training Season: A Systematic Review

BACKGROUND

Endurance athletes perform periodized training in order to prepare for main competitions and maximize performance. However, the coupling between alterations of total energy expenditure (TEE), energy intake, and body composition during different seasonal training phases is unclear. So far, no systematic review has assessed fluctuations in TEE, energy intake, and/or body composition in endurance athletes across the training season. The purpose of this study was to (1) systematically analyze TEE, energy intake, and body composition in highly trained athletes of various endurance disciplines and of both sexes and (2) analyze fluctuations in these parameters across the training season.

METHODS

An electronic database search was conducted on the SPORTDiscus and MEDLINE (January 1990-31 January 2015) databases using a combination of relevant keywords. Two independent reviewers identified potentially relevant studies. Where a consensus was not reached, a third reviewer was consulted. Original research articles that examined TEE, energy intake, and/or body composition in 18-40-year-old endurance athletes and reported the seasonal training phases of data assessment were included in the review. Articles were excluded if body composition was assessed by skinfold measurements, TEE was assessed by questionnaires, or data could not be split between the sexes. Two reviewers assessed the quality of studies independently. Data on subject characteristics, TEE, energy intake, and/or body composition were extracted from the included studies. Subjects were categorized according to their sex and endurance discipline and each study allocated a weight within categories based on the number of subjects assessed. Extracted data were used to calculate weighted means and standard deviations for parameters of TEE, energy intake, and/or body composition.

RESULTS

From 3589 citations, 321 articles were identified as potentially relevant, with 82 meeting all of the inclusion criteria. TEE of endurance athletes was significantly higher during the competition phase than during the preparation phase (p < 0.001) and significantly higher than energy intake in both phases (p < 0.001). During the competition phase, both body mass and fat-free mass were significantly higher compared to other seasonal training phases (p < 0.05).

CONCLUSIONS

Limitations of the present study included insufficient data being available for all seasonal training phases and thus low explanatory power of single parameters. Additionally, the classification of the different seasonal training phases has to be discussed. Male and female endurance athletes show important training seasonal fluctuations in TEE, energy intake, and body composition. Therefore, dietary intake recommendations should take into consideration other factors including the actual training load, TEE, and body composition goals of the athlete.

Dietary Recommendations for Cyclists during Altitude Training

The concept of altitude or hypoxic training is a common practice in cycling. However, several strategies for training regimens have been proposed, like "live high, train high" (LH-TH), "live high, train low" (LH-TL) or "intermittent hypoxic training" (IHT). Each of them combines the effect of acclimatization and different training protocols that require specific nutrition. An appropriate nutrition strategy and adequate hydration can help athletes achieve their fitness and performance goals in this unfriendly environment. In this review, the physiological stress of altitude exposure and training will be discussed, with specific nutrition recommendations for athletes training under such conditions. However, there is little research about the nutrition demands of athletes who train at moderate altitude. Our review considers energetic demands and body mass or body composition changes due to altitude training, including respiratory and urinary water loss under these conditions. Carbohydrate intake recommendations and hydration status are discussed in detail, while iron storage and metabolism is also considered. Last, but not least the risk of increased oxidative stress under hypoxic conditions and antioxidant supplementation suggestions are presented.

Effect of N-acetylcysteine on cycling performance after intensified training

PURPOSE

This investigation examined the ergogenic effect of short-term oral N-acetylcysteine (NAC) supplementation and the associated changes in redox balance and inflammation during intense training.

METHODS

A double-blind randomized placebo-controlled crossover design was used to assess 9 d of oral NAC supplementation (1200 mg·d) in 10 well-trained triathletes. For each supplement trial (NAC and placebo), baseline venous blood and urine samples were taken, and a presupplementation cycle ergometer race simulation was performed. After the loading period, further samples were collected preexercise, postexercise, and 2 and 24 h after the postsupplementation cycle ergometer race simulation. Changes in total antioxidant capacity, ferric reducing ability of plasma, reduced glutathione, oxidized glutathione, thiobarbituric acid-reactive substances, interleukin 6, xanthine oxidase, hypoxanthine, monocyte chemotactic protein 1, nuclear factor κB, and urinary 15-isoprostane F2t concentration were assessed. The experimental procedure was repeated with the remaining supplement after a 3-wk washout. Eight participants completed both supplementation trials.

RESULTS

NAC improved sprint performance during the cycle ergometer race simulation (P < 0.001, ηp = 0.03). Supplementation with NAC also augmented postexercise plasma total antioxidant capacity (P = 0.005, ηp = 0.19), reduced exercise-induced oxidative damage (plasma thiobarbituric acid-reactive substances, P = 0.002, ηp = 0.22; urinary 15-isoprostane F2t concentration, P = 0.010, ηp = 0.431), attenuated inflammation (plasma interleukin 6, P = 0.002, ηp = 0.22; monocyte chemotactic protein 1, P = 0.012, ηp = 0.17), and increased postexercise nuclear factor κB activity (P < 0.001, ηp = 0.21).

CONCLUSION

Oral NAC supplementation improved cycling performance via an improved redox balance and promoted adaptive processes in well-trained athletes undergoing strenuous physical training.

Low serum selenium level is associated with low muscle mass in the community-dwelling elderly

OBJECTIVES

Elderly persons with low muscle mass (LMM) or sarcopenia are prone to frailty and functional decline. This study aimed to investigate the relationship between serum selenium level and skeletal muscle mass in community-dwelling elderly.

DESIGN

Cross-sectional observational study.

SETTING AND PARTICIPANTS

A total of 327 elderly Taipei citizens (mean age 71.5 ± 4.7 years) were recruited from the community.

MEASUREMENTS

Skeletal muscle mass was measured by bioelectrical impedance analysis. LMM was defined by low skeletal muscle index (SMI: muscle mass (kg)/[height (m)](2)). All participants were further divided into quartiles by serum selenium level and the risk for LMM among these quartiles was examined using multivariate logistic regression analyses. Estimated serum selenium levels for the LMM group vs the normal group and estimated SMI in the quartiles of serum selenium were computed by least square method in linear regression models.

RESULTS

The estimated mean (±standard deviation) of serum selenium level was significantly lower in the LMM group compared with the normal group after adjusting for confounders (1.01 ± 0.03 μmol/L vs 1.14 ± 0.02 μmol/L, P < .001). After adjusting for age, sex, lifestyle, and physical and metabolic factors, the odds ratios (95% confidence interval, P value) of LMM in the bottom, second, and third selenium quartile groups were 4.62 (95% CI 2.11-10.10, P < .001), 2.30 (95% CI 1.05-5.03, P < .05) and 1.51 (95% CI 0.66-3.46, P = .327), respectively, compared with the top quartile group of serum selenium level. The least square mean of SMI increased with the quartiles of serum selenium (P < .001).

CONCLUSIONS

This is the first study to demonstrate that low serum selenium is independently associated with low muscle mass in the elderly. The causality and underlying mechanism between selenium and low muscle mass or sarcopenia warrant further research.

Dietary strategies to recover from exercise-induced muscle damage

Exhaustive or unaccustomed intense exercise can cause exercise-induced muscle damage (EIMD) and its undesirable consequences may decrease the ability to exercise and to adhere to a training programme. This review briefly summarises the muscle damage process, focusing predominantly on oxidative stress and inflammation as contributing factors, and describes how nutrition may be positively used to recover from EIMD. The combined intake of carbohydrates and proteins and the use of antioxidants and/or anti-inflammatory nutrients within physiological ranges are interventions that may assist the recovery process. Although the works studying food instead of nutritional supplements are very scarce, their results seem to indicate that food might be a favourable option as a recovery strategy. To date, the only tested foods were milk, cherries, blueberries and pomegranate with promising results. Other potential solutions are foods rich in protein, carbohydrates, antioxidants and/or anti-inflammatory nutrients.

Effect of dietary antioxidants, training, and performance correlates on antioxidant status in competitive rowers

The beneficial effects of exercise and a healthy diet are well documented in the general population but poorly understood in elite athletes. Previous research in subelite athletes suggests that regular training and an antioxidant-rich diet enhance antioxidant defenses but not performance.

PURPOSE

To investigate whether habitual diet and/or exercise (training status or performance) affect antioxidant status in elite athletes.

METHODS

Antioxidant blood biomarkers were assessed before and after a 30-min ergometer time trial in 28 male and 34 female rowers. The antioxidant blood biomarkers included ascorbic acid, uric acid, total antioxidant capacity (TAC), erythrocyte- superoxide dismutase, glutathione peroxidase (GPx), and catalase. Rowers completed a 7-d food diary and an antioxidant-intake questionnaire. Effects of diet, training, and performance on resting biomarkers were assessed with Pearson correlations, and their effect on exercise-induced changes in blood biomarkers was assessed by a method of standardization.

RESULTS

With the exception of GPx, there were small to moderate increases with exercise for all markers. Blood resting TAC had a small correlation with total antioxidant intake (correlation .29; 90% confidence limits, ±.27), and the exercise-induced change in TAC had a trivial to small association with dietary antioxidant intake from vitamin C (standardized effect .19; ±.22), vegetables (.20; ±.23), and vitamin A (.25; ±.27). Most other dietary intakes had trivial associations with antioxidant biomarkers. Years of training had a small inverse correlation with TAC (-.32; ±.19) and a small association with the exercise-induced change in TAC (.27; ±.24).

CONCLUSION

Training status correlates more strongly with antioxidant status than diet does.

Pilot study: Effects of drinking hydrogen-rich water on muscle fatigue caused by acute exercise in elite athletes

Background

Muscle contraction during short intervals of intense exercise causes oxidative stress, which can play a role in the development of overtraining symptoms, including increased fatigue, resulting in muscle microinjury or inflammation. Recently it has been said that hydrogen can function as antioxidant, so we investigated the effect of hydrogen-rich water (HW) on oxidative stress and muscle fatigue in response to acute exercise.

Methods

Ten male soccer players aged 20.9 ± 1.3 years old were subjected to exercise tests and blood sampling. Each subject was examined twice in a crossover double-blind manner; they were given either HW or placebo water (PW) for one week intervals. Subjects were requested to use a cycle ergometer at a 75 % maximal oxygen uptake (VO₂) for 30 min, followed by measurement of peak torque and muscle activity throughout 100 repetitions of maximal isokinetic knee extension. Oxidative stress markers and creatine kinase in the peripheral blood were sequentially measured.

Results

Although acute exercise resulted in an increase in blood lactate levels in the subjects given PW, oral intake of HW prevented an elevation of blood lactate during heavy exercise. Peak torque of PW significantly decreased during maximal isokinetic knee extension, suggesting muscle fatigue, but peak torque of HW didn’t decrease at early phase. There was no significant change in blood oxidative injury markers (d-ROMs and BAP) or creatine kinease after exercise.

Conclusion

Adequate hydration with hydrogen-rich water pre-exercise reduced blood lactate levels and improved exercise-induced decline of muscle function. Although further studies to elucidate the exact mechanisms and the benefits are needed to be confirmed in larger series of studies, these preliminary results may suggest that HW may be suitable hydration for athletes.

Antioxidant supplementation during exercise training: beneficial or detrimental?

High levels of reactive oxygen species (ROS) produced in skeletal muscle during exercise have been associated with muscle damage and impaired muscle function. Supporting endogenous defence systems with additional oral doses of antioxidants has received much attention as a noninvasive strategy to prevent or reduce oxidative stress, decrease muscle damage and improve exercise performance. Over 150 articles have been published on this topic, with almost all of these being small-scale, low-quality studies. The consistent finding is that antioxidant supplementation attenuates exercise-induced oxidative stress. However, any physiological implications of this have yet to be consistently demonstrated, with most studies reporting no effects on exercise-induced muscle damage and performance. Moreover, a growing body of evidence indicates detrimental effects of antioxidant supplementation on the health and performance benefits of exercise training. Indeed, although ROS are associated with harmful biological events, they are also essential to the development and optimal function of every cell. The aim of this review is to present and discuss 23 studies that have shown that antioxidant supplementation interferes with exercise training-induced adaptations. The main findings of these studies are that, in certain situations, loading the cell with high doses of antioxidants leads to a blunting of the positive effects of exercise training and interferes with important ROS-mediated physiological processes, such as vasodilation and insulin signalling. More research is needed to produce evidence-based guidelines regarding the use of antioxidant supplementation during exercise training. We recommend that an adequate intake of vitamins and minerals through a varied and balanced diet remains the best approach to maintain the optimal antioxidant status in exercising individuals.

Dietary intakes and antioxidant status in mind-body exercising pre- and postmenopausal women

OBJECTIVE

The decline in antioxidant defenses due to both estrogen loss and frequent adoption of poor dietary choices exposes postmenopausal women to cardiovascular diseases. Adequate nutrition and physical exercise are two factors of health promotion. This study investigated whether regular practice of mind-body exercise (yoga and/or tai chi) alters dietary intake and antioxidant status and balances the menopause-related increases in lipid peroxidation and cardiovascular risk.

DESIGN

Cross-sectional study.

SETTING

The study was conducted in an urban community in Bangkok (Thailand) between May and August 2007.

PARTICIPANTS

Premenopausal (Pre M; 39±8 yrs; n=56) and postmenopausal (Post M; 54±5 yrs; n=39) women who had been practicing yoga (Y) and/or tai chi (TC) more than 3 hours/week for a year, or who had no regular physical activity practice (sedentary, S).

MEASUREMENTS

All participants completed food frequency questionnaires and 4-day food and activity records. Blood was collected on day 5. Factorial ANOVA tests were performed according to menopause status, exercise, and hormone replacement therapy (HRT) groups.

RESULTS

Post M had higher (p = 0.01) dietary fiber intake compared with Pre M. Yoga practitioners had lower BMI (p = 0.004) and lower fat intake (p = 0.02) compared with their S and TC counterparts. Plasma total antioxidant status was significantly and independently lower and higher in Y and Post M groups, respectively. However, no difference was shown after adjusting for BMI. Regardless of menopause status and HRT, the activity of erythrocyte glutathione peroxidase - an aerobic training-responsive enzyme - was higher (p < 0.001) in TC practitioners compared with other groups. No effects were shown on erythrocyte superoxide dismutase activity, plasma lipid peroxidation (TBARS) or total homocysteine concentrations.

CONCLUSION

Yoga and tai chi exercises can be used as components of a strategy to promote healthy lifestyles (balanced diet and moderate intensity exercise) in vulnerable populations, such as menopausal women, in order to prevent aging induced oxidative stress-related diseases.

Effects of tai chi training on antioxidant capacity in pre- and postmenopausal women

The risk of oxidative stress-related metabolic diseases increases with menopause and physical inactivity. We hypothesized that an 8-week Tai Chi (TC) training program (2 sessions in class; 2 sessions at home; 1-1:15/session) would improve antioxidant capacity and reduce cardiovascular risks in both pre- (n = 8) and postmenopausal (n = 7) sedentary women. Selected measures of physical fitness and blood parameters were analyzed before and after the program. Besides the well-known effects of TC on balance, flexibility, and maximum leg extensor strength, TC (1) increased erythrocyte glutathione peroxidase activity—an aerobic training-responsive antioxidant enzyme—and plasma total antioxidant status and (2) decreased plasma total homocysteine, a cardiovascular risk marker. In addition to being a low-velocity, low-impact, and relatively safe, TC is a suitable physical activity design for pre- and postmenopausal women to increase antioxidant defenses. Investigating breathing effects during TC movements would be an interesting area for further research in diseases prevention.

Redox homeostasis, oxidative stress and disuse muscle atrophy

A pivotal role has been ascribed to oxidative stress in determining the imbalance between protein synthesis and degradation leading to muscle atrophy in many pathological conditions and in disuse. However, a large variability in disuse-induced alteration of redox homeostasis through muscles, models and species emerges from the literature. Whereas the causal role of oxidative stress appears well established in the mechanical ventilation model, findings are less compelling in the hindlimb unloaded mice and very limited in humans. The mere coexistence of muscle atrophy, indirect indexes of increased reactive oxygen species (ROS) production and impairment of antioxidant defence systems, in fact, does not unequivocally support a causal role of oxidative stress in the phenomenon. We hypothesise that in some muscles, models and species only, due to a large redox imbalance, the leading phenomena are activation of proteolysis and massive oxidation of proteins, which would become more susceptible to degradation. In other conditions, due to a lower extent and variable time course of ROS production, different ROS-dependent, but also -independent intracellular pathways might dominate determining the variable extent of atrophy and even dispensable protein oxidation. The ROS production and removal are complex and finely tuned phenomena. They are indeed important intracellular signals and redox balance maintains normal muscle homeostasis and can underlie either positive or negative adaptations to exercise. A precise approach to determine the levels of ROS in living cells in various conditions appears to be of paramount importance to define and support such hypotheses.

Antioxidant responses to an acute ultra-endurance exercise: impact on DNA stability and indications for an increased need for nutritive antioxidants in the early recovery phase

Antioxidant requirements have neither been defined for endurance nor been defined for ultra-endurance athletes. To verify whether an acute bout of ultra-endurance exercise modifies the need for nutritive antioxidants, we aimed (1) to investigate the changes of endogenous and exogenous antioxidants in response to an Ironman triathlon; (2) to particularise the relevance of antioxidant responses to the indices of oxidatively damaged blood lipids, blood cell compounds and lymphocyte DNA and (3) to examine whether potential time-points of increased susceptibility to oxidative damage are associated with alterations in the antioxidant status. Blood that was collected from forty-two well-trained male athletes 2 d pre-race, immediately post-race, and 1, 5 and 19 d later was sampled. The key findings of the present study are as follows: (1) Immediately post-race, vitamin C, α-tocopherol, and levels of the Trolox equivalent antioxidant capacity, the ferric reducing ability of plasma and the oxygen radical absorbance capacity (ORAC) assays increased significantly. Exercise-induced changes in the plasma antioxidant capacity were associated with changes in uric acid, bilirubin and vitamin C. (2) Significant inverse correlations between ORAC levels and indices of oxidatively damaged DNA immediately and 1 d post-race suggest a protective role of the acute antioxidant responses in DNA stability. (3) Significant decreases in carotenoids and γ-tocopherol 1 d post-race indicate that the antioxidant intake during the first 24 h of recovery following an acute ultra-endurance exercise requires specific attention. Furthermore, the present study illustrates the importance of a diversified and well-balanced diet to maintain a physiological antioxidant status in ultra-endurance athletes in reference to recommendations.

Antioxidant status of elite athletes remains impaired 2 weeks after a simulated altitude training camp

BACKGROUND

It has been shown that the antioxidant status was altered by the "live high-train low" (LHTL) method, however, no information is available regarding the antioxidant restoration during the recovery period.

AIM OF THE STUDY

We tested the hypothesis that the antioxidant status is impaired by 18 days LHTL in elite athletes and remained altered after 14 days of recovery.

METHODS

Eleven elite cross-country skiers from the French Skiing Federation were submitted to 18-day endurance training. Six (hypoxic group; HG) trained at 1,200 m and lived in hypoxia (simulated altitude of 2,500 m-3,000 m-3,500 m) and 5 (control group; CG) trained and lived at 1,200 m. Plasma levels of advanced oxidation protein products (AOPP), malondialdehydes (MDA), ferric reducing antioxidant power (FRAP), trolox equivalent antioxidant capacity (TEAC) lipid-soluble antioxidants (alpha-tocopherol, beta-carotene and lycopene) were measured at rest, before (PRE), the first day after (POST1) and again 2 weeks (POST14) after the training. Intakes of vitamins A and E were evaluated from the dietary recording.

RESULTS

In POST1, FRAP and TEAC decreased in both groups, however, the TEAC decrease persisted in POST14 for HG only. Lycopene and beta-carotene decreased in POST1 for HG and remained lower in POST14. Finally, AOPP increased only for HG in POST1. The general decline of antioxidant status for both groups might result from insufficient intakes in vitamins A and E.

CONCLUSION

This is the first study to show that the antioxidant status did not return to baseline 2 weeks after 18 days of LHTL training.

Antioxidant status, oxidative stress, and damage in elite kayakers after 1 year of training and competition in 2 seasons

The large volume of training performed by elite athletes throughout the season can translate into a chronic oxidative insult. To study the effects that chronically high training loads have on athletes’ redox status, superoxide dismutase (SOD), glutathione reductase, glutathione peroxidase (GPx), and creatine kinase activities; total antioxidant status (TAS); and uric acid, retinol, α-tocopherol, α-carotene, β-carotene, lycopene, lutein + zeaxanthin, vitamin C, thiobarbituric acid reactive substances (TBARS), interleukin-6, and cortisol levels were determined in 9 kayakers (6 men) in a competitive period during the first season (June, T1), and in precompetitive (March, T2) and competitive (June, T3) periods during the following season. TAS decreased from the first to the second season (T1 vs. T2, p < 0.001; T1 vs. T3, p < 0.001). TBARS (p = 0.024) decreased from T1 to T2. The α-tocopherol increase (p = 0.001) from T1 to T2 lost statistical significance after adjustment for total lipids (p = 0.243). GPx (p = 0.003) increased, while SOD (p < 0.001) and uric acid (p = 0.032) decreased from T2 to T3. Cortisol levels decreased significantly throughout the study (T1 vs. T2, p = 0.042; T2 vs. T3, p = 0.018; T1 vs. T3, p = 0.002). No significant differences were observed for any of the other parameters studied. Antioxidant status changed more within the same season than from one season to another. Redox markers should be monitored throughout the season to detect athletes at an increased oxidative risk.

Endurance exercise and DNA stability: is there a link to duration and intensity?

It is commonly accepted that regular moderate intensity physical activity reduces the risk of developing many diseases. Counter intuitively, however, evidence also exists for oxidative stress resulting from acute and strenuous exercise. Enhanced formation of reactive oxygen and nitrogen species may lead to oxidatively modified lipids, proteins and nucleic acids and possibly disease. Currently, only a few studies have investigated the influence of exercise on DNA stability and damage with conflicting results, small study groups and the use of different sample matrices or methods and result units. This is the first review to address the effect of exercise of various intensities and durations on DNA stability, focusing on human population studies. Furthermore, this article describes the principles and limitations of commonly used methods for the assessment of oxidatively modified DNA and DNA stability. This review is structured according to the type of exercise conducted (field or laboratory based) and the intensity performed (i.e. competitive ultra/endurance exercise or maximal tests until exhaustion). The findings presented here suggest that competitive ultra-endurance exercise (>4h) does not induce persistent DNA damage. However, when considering the effects of endurance exercise (<4h), no clear conclusions could be drawn. Laboratory studies have shown equivocal results (increased or no oxidative stress) after endurance or exhaustive exercise. To clarify which components of exercise participation (i.e. duration, intensity and training status of subjects) have an impact on DNA stability and damage, additional carefully designed studies combining the measurement of DNA damage, gene expression and DNA repair mechanisms before, during and after exercise of differing intensities and durations are required.

Does physical exercise modify antioxidant requirements?

Physical training is known to induce a biochemical adaptive response which might require an increase in the ingestion and/or the absorption of micronutrients. A question that is still being raised is whether acute or chronic exercise modifies antioxidant requirements. First, the present review brings to light the most crucial studies on the topic. Second, it interprets the established relationships between antioxidant micronutrient intakes and the adaptive response of antioxidant systems. Finally, it exposes the major questions connected with antioxidant micronutrient requirements for athletes. To this effect, the training-load interaction with nutrition is taken into account. As oxidative stress cannot be avoided, the imbalance between oxidants and antioxidants can be alleviated to minimise oxidative damage and outcomes. There is growing evidence that one specific antioxidant cannot by itself prevent oxidative stress-induced damage, as direct adverse effects of supplementation are attributed to undesirable synergic effects. Other effects can be supposed that limit the endogenous adaptive effect of training. High doses of antioxidant supplements can minimise the effects of radical oxygen species themselves or generate pro-oxidant effects. Effects are only exhibited when nutritional status is deficient. There are no convincing effects of supplementation in well-trained athletes. Risk/benefit analysis emerges on evidence for an unknown risk of supranutritional intakes, a supposed impairment of adaptive effects and a still unknown long-term risk. Appropriate status can be achieved by a diversified and balanced diet, adapted to specific needs, by awareness of high-density food intakes (avoiding products containing a low density of micronutrients).

Acute exercise and oxidative stress: a 30 year history

The topic of exercise-induced oxidative stress has received considerable attention in recent years, with close to 300 original investigations published since the early work of Dillard and colleagues in 1978. Single bouts of aerobic and anaerobic exercise can induce an acute state of oxidative stress. This is indicated by an increased presence of oxidized molecules in a variety of tissues. Exercise mode, intensity, and duration, as well as the subject population tested, all can impact the extent of oxidation. Moreover, the use of antioxidant supplements can impact the findings. Although a single bout of exercise often leads to an acute oxidative stress, in accordance with the principle of hormesis, such an increase appears necessary to allow for an up-regulation in endogenous antioxidant defenses. This review presents a comprehensive summary of original investigations focused on exercise-induced oxidative stress. This should provide the reader with a well-documented account of the research done within this area of science over the past 30 years.

A network biology model of micronutrient related health

Micronutrients are involved in specific biochemical pathways and have dedicated functions in the body, but they are also interconnected in complex metabolic networks, such as oxidative-reductive and inflammatory pathways and hormonal regulation, in which the overarching function is to optimise health. Post-genomic technologies, in particular metabolomics and proteomics, both of which are appropriate for plasma samples, provide a new opportunity to study the metabolic effects of micronutrients in relation to optimal health. The study of micronutrient-related health status requires a combination of data on markers of dietary exposure, markers of target function and biological response, health status metabolites, and disease parameters. When these nutrient-centred and physiology/health-centred parameters are combined and studied using a systems biology approach with bioinformatics and multivariate statistical tools, it should be possible to generate a micronutrient phenotype database. From this we can explore external factors that define the phenotype, such as lifestage and lifestyle, and the impact of genotype, and the results can also be used to define micronutrient requirements and provide dietary advice. New mechanistic insights have already been developed using biological network models, for example genes and protein-protein interactions in the aetiology of type 2 diabetes mellitus. It is hoped that the challenge of applying this approach to micronutrients will, in time, result in a change from micronutrient oriented to a health oriented views and provide a more holistic understanding of the role played by multiple micronutrients in the maintenance of homeostasis and prevention of chronic disease, for example through their involvement in oxidation and inflammation.

An open-label dose-response study of lymphocyte glutathione levels in healthy men and women receiving pressurized whey protein isolate supplements

BACKGROUND

High-pressure treatment of whey protein may increase digestibility and bioavailability of cysteine. The purpose of the study was to determine whether total lymphocyte glutathione (gamma-glutamyl-cysteinyl-glycine [GSH]) levels (oxidized+reduced) can be augmented from three different doses of pressurized whey protein supplements in a dose-dependent manner over a 2-week period.

METHODS

Eighteen healthy males and 18 healthy females were randomized into three different groups, with 31 finishing the study. Each group ingested 15, 30, or 45 g/day pressurized whey protein in the morning in bar format for 14 days. Each group was blinded to the amount of whey protein they were ingesting. Ten millilitres of blood was withdrawn before and after the 2-week period to assess blood lymphocyte levels pre and post supplementation.

RESULTS

There was no change in body weight or reported physical activity levels pre and post supplementation. Pre-lymphocyte GSH levels were not significantly different between groups (3.7+/-0.7 micromol/l). Least-squares linear regression showed that the change in lymphocyte GSH levels from pre to post supplementation was affected by the amount of whey protein ingested daily (P=0.037). The group that ingested 45 g/day pressurized whey protein augmented GSH levels the most (by approximately 24%), and the group that ingested 15 g/day did not increase lymphocyte GSH levels.

CONCLUSIONS

We conclude that there is a significant relationship between the dosage of supplementation and the change in lymphocyte GSH levels. Furthermore, the increase in GSH was linear with the amount of whey protein ingested. Pressurized whey protein supplementation of 45 g/day for 2 weeks can increase lymphocyte GSH by 24%.

Phenotypes of chronic obstructive pulmonary disease

The current clinical classification of smoking-related lung disease fails to take into account the heterogeneity of chronic obstructive pulmonary disease (COPD). With an increased understanding of pathophysiologic variation, COPD now clearly represents a spectrum of overlapping diseases with important extrapulmonary consequences. A "phenotype" describes the outward physical manifestations of a particular disease, and compromises anything that is part of the observable structure, function or behavior of an individual. Such phenotypic distinctions in COPD include: frequent exacerbator, pulmonary cachectic, rapid decliner, airways hyperresponsiveness, impaired exercise tolerance, and emphysema versus airways disease. These variable manifestations, each with unique prognostic, clinical and physiologic ramifications, represent distinct phenotypes within COPD. While all of these phenotypes have smoking as a common risk factor, the other risk factors that determine these phenotypes remain poorly understood. An individual smoker has variable expression of each phenotype and there is mounting evidence that COPD phenotypes have different clinical outcomes. These phenotypes can be broadly classified into one of three groups: clinical, physiologic and radiographic. This review presents the evidence for the spectrum of COPD phenotypes with a focused discussion on the pathophysiologic, epidemiologic and clinical significance of each subtype.

Contribution of selected vitamins and trace elements to immune function

Adequate intakes of vitamins and trace elements are required for the immune system to function efficiently. Micronutrient deficiency suppresses immune functions by affecting the innate T-cell-mediated immune response and adaptive antibody response, and leads to dysregulation of the balanced host response. This increases the susceptibility to infections, with increased morbidity and mortality. In turn, infections aggravate micronutrient deficiencies by reducing nutrient intake, increasing losses, and interfering with utilization by altering metabolic pathways. Insufficient intake of micronutrients occurs in people with eating disorders, in smokers (both active and passive), in individuals with chronic alcohol abuse, in patients with certain diseases, during pregnancy and lactation, and in the elderly. With aging a variety of changes are observed in the immune system, which translate into less effective innate and adaptive immune responses and increased susceptibility to infections. Antioxidant vitamins and trace elements (vitamins C, E, selenium, copper, and zinc) counteract potential damage caused by reactive oxygen species to cellular tissues and modulate immune cell function through regulation of redox-sensitive transcription factors and affect production of cytokines and prostaglandins. Adequate intake of vitamins B(6), folate, B(12), C, E, and of selenium, zinc, copper, and iron supports a Th1 cytokine-mediated immune response with sufficient production of proinflammatory cytokines, which maintains an effective immune response and avoids a shift to an anti-inflammatory Th2 cell-mediated immune response and an increased risk of extracellular infections. Supplementation with these micronutrients reverses the Th2 cell-mediated immune response to a proinflammatory Th1 cytokine-regulated response with enhanced innate immunity. Vitamins A and D play important roles in both cell-mediated and humoral antibody response and support a Th2-mediated anti-inflammatory cytokine profile. Vitamin A deficiency impairs both innate immunity (mucosal epithelial regeneration) and adaptive immune response to infection resulting in an impaired ability to counteract extracellular pathogens. Vitamin D deficiency is correlated with a higher susceptibility to infections due to impaired localized innate immunity and defects in antigen-specific cellular immune response. Overall, inadequate intake and status of these vitamins and minerals may lead to suppressed immunity, which predisposes to infections and aggravates malnutrition.

Nutritional and Plasmatic Antioxidant Vitamins Status of Ultra Endurance Athletes

OBJECTIVE

The "Marathon des Sables" (MDS) is a competition known to induce oxidative stress. Antioxidant vitamins prevent exercise-induced oxidative damages. The purpose of this study was to evaluate daily intake and plasma level of the main antioxidant vitamins (alpha-tocopherol, vitamin C, beta-carotene and retinol) in 19 male athletes who participated in this competition.

METHODS

Data collected before the beginning of the competition included daily dietary intake using a 7-day food record and plasma biochemical measurements (alpha-tocopherol, vitamin C, beta-carotene and retinol).

RESULTS

First, total energy intake was obviously lower than the energetic intake usually observed in well-trained endurance athletes. Second, antioxidant vitamins intake was also insufficient. Indeed, the intake was lower than the French Dietary Reference Intakes (DRI) for this population in 18 subjects for vitamin E and 6 subjects for vitamin C, beta-carotene and Retinol Equivalent. As a significant relationship was found between total energy intake and the intake of vitamin E (r = 0.73; p < 0.001) and vitamin C (r = 0.78; p < 0.001), the low total energy intake contributed partially to the insufficient antioxidant vitamins intake. The dietary questionnaire analysis also revealed a low intake of vegetable oils, fruits and vegetables. However, plasma concentrations of these antioxidant vitamins were similar to the literature data observed in athletes.

CONCLUSION

This study evidenced obvious insufficient energy intake in ultra endurance athletes associated with a low antioxidant vitamin intake.

Multivitamin-mineral supplementation prevents lipid peroxidation during "the Marathon des Sables"

OBJECTIVE

We investigated the effect of a moderate mutivitamin and mineral supplementation containing mainly vitamin C (150.0 mg.day(-1)), vitamin E (24.0 mg.day(-1)) and beta-carotene (4.8 mg.day(-1)) prior to and during an extreme running competition -the Marathon des Sables (MDS)- that consisted of six long races in the desert.

METHODS

Seventeen athletes participated in our double blind, placebo-controlled study. Blood samples were collected prior to the supplementation i.e. three weeks before the competition (D-21), two days prior to the MDS (D-2), after the third race (D3) and at the end of the competition (D7). Erythrocyte antioxidant enzyme activity (glutathione peroxidase (GPx), superoxide dismutase (SOD)), erythrocyte glutathione level (GSH), plasma non-enzymatic antioxidant status (uric acid, vitamin C, alpha-tocopherol, retinol, beta-carotene), markers of plasma lipid peroxidation (thiobarbituric reactive substances (TBARS)), reactive carbonyl derivatives (RCD) and membrane damage (creatine kinase and lactate dehydrogenase activities) were measured.

RESULTS

In both groups, GSH levels, uric acid levels and membrane damage significantly increased during the competition while SOD activity significantly decreased. In Supplemented group, plasma alpha-tocopherol, beta-carotene and retinol levels significantly increased after three weeks of supplementing. In contrast to Placebo group, alpha-tocopherol, vitamin C and retinol levels were significantly affected by the competition in Supplemented group. Moreover, no increase in TBARS was observed in Supplemented group during the competition, whereas TBARS significantly increased at D3 in the placebo group.

CONCLUSION

The moderate multivitamin-mineral supplementation prevented the transient increase in TBARS levels during this extreme competition.

Blood cells as functional markers of antioxidant vitamin status

Antioxidants have shown beneficial effects in several biological systems, in which they were able to prevent oxidative stress-associated damage. Vitamins C and E are key antioxidants in man. Dietary intake cannot accurately reflect plasma vitamin levels. However, the plasma levels of antioxidant vitamins could also reflect the acute assimilation of these vitamins. It has been pointed out that antioxidant vitamin blood contents reach a saturation level by intake of dietary supplements. Antioxidant vitamin plasma levels are the parameter most used to determine antioxidant status. However, the vitamin plasma levels may not reflect the nutritional status of vitamins. It has been pointed out that the vitamin E in adipose tissue can be used as a measure of vitamin E status. To determinate antioxidant vitamin contents in lymphocytes and neutrophils after exercise is a useful tool to assess the functional status of antioxidant vitamins.

Oxidative stress : relationship with exercise and training

Free radicals are reactive compounds that are naturally produced in the human body. They can exert positive effects (e.g. on the immune system) or negative effects (e.g. lipids, proteins or DNA oxidation). To limit these harmful effects, an organism requires complex protection - the antioxidant system. This system consists of antioxidant enzymes (catalase, glutathione peroxidase, superoxide dismutase) and non-enzymatic antioxidants (e.g. vitamin E [tocopherol], vitamin A [retinol], vitamin C [ascorbic acid], glutathione and uric acid). An imbalance between free radical production and antioxidant defence leads to an oxidative stress state, which may be involved in aging processes and even in some pathology (e.g. cancer and Parkinson's disease). Physical exercise also increases oxidative stress and causes disruptions of the homeostasis. Training can have positive or negative effects on oxidative stress depending on training load, training specificity and the basal level of training. Moreover, oxidative stress seems to be involved in muscular fatigue and may lead to overtraining.

Respiratory loading intensity and diaphragm oxidative stress:N-acetyl-cysteine effects

We hypothesized that resistive breathing of moderate to high intensity might increase diaphragm oxidative stress, which could be partially attenuated by antioxidants. Our objective was to assess the levels of oxidative stress in the dog diaphragm after respiratory muscle training of a wide range of intensities and whether N-acetyl-cysteine (NAC) might act as an antioxidant. Twelve Beagle dogs were anesthetized with 1% propophol, tracheostomized, and subjected to continuous inspiratory resistive breathing (IRB) (2 h/day for 2 wk). They were further divided into two groups ( n = 6): NAC group (oral NAC administration/24 h for 14 days) and control group (placebo). Diaphragm biopsies were obtained before (baseline biopsy) and after (contralateral hemidiaphragm) IRB and NAC vs. placebo treatment. Oxidative stress was evaluated in all diaphragm biopsies through determination of 3-nitrotyrosine immunoreactivity, protein carbonylation, hydroxynoneal protein adducts, Mn-SOD, and catalase, using immunoblotting and immunohistochemistry. Both protein tyrosine nitration and protein carbonylation were directly related to the amount of the respiratory loads, and NAC treatment abrogated this proportional rise in these two indexes of oxidative stress in response to increasing inspiratory loads. A post hoc analysis revealed that only the diaphragms of dogs subjected to high-intensity loads showed a significant increase in both protein tyrosine nitration and carbonylation, which were also significantly reduced by NAC treatment. These results suggest that high-intensity respiratory loading-induced oxidative stress may be neutralized by NAC treatment during IRB in the canine diaphragm.

Increase in selenium requirements with physical activity loads in well-trained athletes is not linear

Selenium requirements in athletes are supposed to be increased with energy expenditure (EE) to preserve selenium status and an optimal antioxidant balance. The question of whether selenium intakes are related to EE and whether plasma selenium status induces up-regulation in erythrocyte endogenous antioxidant defense and decreases plasma oxidative damage markers in athletes was addressed. 118 well-trained athletes completed 7 d food and activities records in a cross-sectional study. Blood was sampled on day 8. Among the athletes, 23% of the males and 66% of the females had selenium intakes below two-third of the French RDA. Plasma selenium concentrations in most of less trained athletes were lower than the postulated concentration to be required to maximize erythrocyte GSH-Px activity. Athletes with the highest daily EE had the highest selenium intakes, percentage of vegetal protein intakes and plasma selenium concentrations. Only 2.6% of the athletes exhibited low plasma selenium concentrations (< 0.75 micromol/l). The relation between plasma selenium and EE was polynomial (r = 0.50; P < 0.005). Erythrocyte GSH-Px activity in athletes was not linked to selenium status. Selenium requirements are increased in athletes without being linearly related to EE.