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      Comparison of the effects of two antioxidant diets on oxidative stress markers in triathletes

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          Abstract

          Intense exercise generates an imbalance in the redox system. However, chronic exercise can yield antioxidant adaptations. A few studies with humans have investigated the effects of antioxidant diets on athletes. Therefore we compared the effects of two dietary interventions on oxidative stress in competitive triathletes. Thirteen male triathletes were selected and divided into 2 groups: one that had a regular antioxidant diet (RE-diet) and the other that had a high antioxidant diet (AO-diet). The diet period was 14 days and blood samples were collected before and after this period. The AO-diet provided twice the dietary reference intake (DRI) of α-tocopherol (30 mg), five times the DRI of ascorbic acid (450 mg), and twice the DRI of vitamin A (1800 g), while the RE-diet provided the DRI of α-tocopherol (15 mg), twice the DRI of ascorbic acid (180 mg) and the DRI of vitamin A (900 μg). The oxidative stress parameters evaluated were: thiobarbituric acid reactive substances (TBARS), total reactive antioxidant potential (TRAP), total sulfhydryl, carbonyl, superoxide dismutase (SOD) activity, hydrogen peroxide consumption and glutathione peroxidase (GPx) activity. We observed, after the diet period, an increase in sulfhydryl, TRAP, TBARS and SOD activity, and a decrease in carbonyl levels. However, no changes were found in hydrogen peroxide consumption or GPx activity. We concluded that antioxidant-enriched diets can improve the redox status of triathletes.

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          Antioxidants prevent health-promoting effects of physical exercise in humans.

          Exercise promotes longevity and ameliorates type 2 diabetes mellitus and insulin resistance. However, exercise also increases mitochondrial formation of presumably harmful reactive oxygen species (ROS). Antioxidants are widely used as supplements but whether they affect the health-promoting effects of exercise is unknown. We evaluated the effects of a combination of vitamin C (1000 mg/day) and vitamin E (400 IU/day) on insulin sensitivity as measured by glucose infusion rates (GIR) during a hyperinsulinemic, euglycemic clamp in previously untrained (n = 19) and pretrained (n = 20) healthy young men. Before and after a 4 week intervention of physical exercise, GIR was determined, and muscle biopsies for gene expression analyses as well as plasma samples were obtained to compare changes over baseline and potential influences of vitamins on exercise effects. Exercise increased parameters of insulin sensitivity (GIR and plasma adiponectin) only in the absence of antioxidants in both previously untrained (P < 0.001) and pretrained (P < 0.001) individuals. This was paralleled by increased expression of ROS-sensitive transcriptional regulators of insulin sensitivity and ROS defense capacity, peroxisome-proliferator-activated receptor gamma (PPARgamma), and PPARgamma coactivators PGC1alpha and PGC1beta only in the absence of antioxidants (P < 0.001 for all). Molecular mediators of endogenous ROS defense (superoxide dismutases 1 and 2; glutathione peroxidase) were also induced by exercise, and this effect too was blocked by antioxidant supplementation. Consistent with the concept of mitohormesis, exercise-induced oxidative stress ameliorates insulin resistance and causes an adaptive response promoting endogenous antioxidant defense capacity. Supplementation with antioxidants may preclude these health-promoting effects of exercise in humans.
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            Determination of carbonyl content in oxidatively modified proteins.

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              Malondialdehyde determination as index of lipid peroxidation.

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                Author and article information

                Journal
                Biol Sport
                Biol Sport
                JBS
                Biology of Sport
                Institute of Sport in Warsaw
                0860-021X
                2083-1862
                30 March 2018
                June 2018
                : 35
                : 2
                : 181-189
                Affiliations
                [1 ]Graduate Program in Human Movement Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
                [2 ]Graduate Program in Rehabilitation Sciences, Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil
                [3 ]Laboratório de Fisiopatologia do Exercício, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
                [4 ]Faculdades Integradas de Taquara, Taquara, Brazil
                [5 ]Laboratório de Estresse Oxidativo, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
                [6 ]Departamento de Fisiologia, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
                Author notes
                Corresponding author: Cláudia D. Schneider, Graduate Program in Rehabilitation Sciences, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA); Rua Sarmento Leite, 245, sala 401b; Porto Alegre; RS; Brazil; Zip Code: 90050-170; Phone: +55 51 33038830; E-mail: claudias@ 123456ufcspa.edu.br , claudia.ds2013@ 123456gmail.com
                Article
                74194
                10.5114/biolsport.2018.74194
                6234303
                30455547
                a08be278-761a-4234-a5e5-2dd2cf405138
                Copyright © Biology of Sport 2018

                This is an Open Access article distributed under the terms of the Creative Commons Attribution-Noncommercial 3.0 Unported License, permitting all non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 21 June 2017
                : 08 August 2017
                : 24 November 2017
                : 12 December 2017
                Categories
                Original Paper

                athletes,antioxidants,oxidative stress,food,vitamins
                athletes, antioxidants, oxidative stress, food, vitamins

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