Thesis (MSc)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: The human body has developed an integrated antioxidant defence system to protect
against free radical damage. Acute exercise may result in the increased generation of free
radicals, including reactive oxygen species, and this may overwhelm antioxidant defence
systems resulting in oxidative stress. However, it has been shown that individuals who
undergo regular exercise training may have improved antioxidant capacity when compared
to sedentary controls. Results from research regarding the association between
antioxidant capacity and exercise training are however not conclusive and further
investigation is required. Therefore, the aim of this study was to investigate the association
between the total plasma antioxidant status and selected plasma indicators of antioxidant
status and the MnSOD Ala-9Val (-28C®T) polymorphism in trained male athletes (rugby
players) and sedentary male students while controlling for dietary intake of the major
antioxidants using a validated dietary assessment method.
In order to address the potential confounding effect of dietary antioxidant intake on
antioxidant status in the main study, a FFQ that measures vitamin C, vitamin E, carotenoid
and flavonoid intake was developed. The reproducibility was assessed by the repeat
administration of the FFQ (n = 38), while the va lidity was assessed using a 28-day closeended
dietary record and repeated plasma vitamin C values (n = 18). Several statistical
tests were conducted to compare the values obtained from the FFQ with values obtained
from the various reference methods. While results from Bland-Altman plots suggested that
the reproducibility and validity of FFQ was not completely satisfactory, similar mean values,
moderate to strong correlation coefficients, and a high percentage of individuals classified
correctly according to quartiles of intake indicated satisfactory reproducibility and validity of
the FFQ in assessing antioxidant intake. Furthermore, moderate to strong validity
coefficients obtained from the method of triads also indicated satisfactory validity for the
FFQ.
The main study involved a cross-sectional study that compared plasma vitamin C and
carotenoid levels as well as total plasma antioxidant status in trained rugby players (n = 76)
and sedentary male subjects (n = 39) with different MnSOD genotypes, while controlling
for dietary antioxidant intake. Rugby players had significantly higher plasma vitamin C and
carotenoid levels compared to sedentary students, which indicated more satisfactory
plasma antioxidant status. This was also reflected in the tendency for total plasma antioxidant status (ORAC assay) to be higher in rugby players than sedentary students.
MnSOD genotype did not influence plasma vitamin C and carotenoid levels or plasma total
antioxidant status, with or without control for dietary antioxidant intake. Dietary vitamin C,
vitamin E, carotenoid an flavonoid intake (from foods + supplements) was similar for rugby
players and sedentary students and was adequate for both groups. Thus the association
between antioxidant status and MnSOD genotype in rugby players and sedentary students
seemed not to be influenced by dietary antioxidant intake. In conclusion therefore, rugby
players undergoing regular exercise training had a more satisfactory antioxidant status
compared to sedentary students. Based on this conclusion, the widespread use of
antioxidant supplements by athletes is questioned. / AFRIKAANSE OPSOMMING: Die menslike liggaam beskik oor ‘n geintegreerde antioksidantmeganisme om dit teen
vryradikaalskade te beskerm. Akute oefening kan bydra tot ‘n verhoogde produksie van
vry radikale, insluitend reaktiewe suurstofspesies, wat kan veroorsaak dat die
antioksidantbeskermingsmeganisme oorlaai word, wat dan kan aanleiding gee tot die
ontstaan van oksidatiewe stress. Dit is aangetoon dat persone wat gereeld oefening doen
verbeterde antioksidantkapasiteit toon in vergelyking met persone wat geen oefening doen
nie. Die resultate van navorsingstudies wat die verband tussen antioksidantkapasiteit en
oefening ondersoek is egter teenstrydig en verdere navorsing op hierdie gebied is
essensieël om uitsluitsel te kry oor kontensieuse vraagstukke. Die doel van hierdie studie
was dus om ondersoek in te stel na die verband tussen plasma antioksidant status, die
MnSOD Ala-9Val (-28C T) polimorfisme en geselekteerde plasma antioksidantmerkers in
geoefende manlike atlete (rugby spelers) en ‘n onaktiewe manlike kontrolegroep terwyl
gekontroleer word vir die dieetinname van die vernaamste antioksidante.
Om vir die potensiële invloed van dieetantioksidantinname op die antioksidantstatus van
proefpersone in die hoofstudie te kontroleer, is ‘n voedsel frekwensievraelys wat vitamien
C-, vitamien E-, karotenoïed- en flavinoïedinname meet, ontwikkel. Die herhaalbaarheid
(betroubaarheid) van die vraelys is getoets deur herhaalde voltooiing daarvan deur ‘n
toetsgroep (n=38), terwyl die geldighied getoets is deur gebruik te maak van ‘n 28-dag
geslote dieetrekord en herhaalde plasma vitamien C bepalings as verwysingswaardes
(n=18). Verskeie statistiese toetse is uitgevoer om die frekwensievraelys waardes met die
verskillende verwysingswaardes te vergelyk. Alhoewel die Bland -Altman grafieke nie dui
op bevredigende herhaalbaarheid en geldigheid van die voedselfrekwensie vraelys nie, dui
gelyke gemiddelde waardes, matig tot sterk en betekenisvolle korrelasiekoeffisiënte en ‘n
hoë persentasie individue korrek geklassifiseer volgens kwartiele van inname, wel op
bevredigende herhaalbaarheid en geldigheid. Matige tot sterk geldigheidskoeffisiënte is
ook verkry met die toepassing van “The method of Triads”, wat verdere steun bied vir
bevredigende geldigheid.
In die hoofstudie is plasma vitamien C, karotenoïedvlakke en totale plasma
antioksidantstatus in manlike rugby spelers (n=76) vergelyk met dié van onaktiewe
manlike kontroles (n=39). Vergelykings tussen MnSOD genotipes binne die
aktiwiteitsgroepe is ook getref. Al genoemde analises is gekontroleer vir dieet antioksidantinname. Resultate dui daarop dat die plasma vitamien C en karotenoïedvlakke
van rugby spelers betekenisvol hoër was as dié van die kontrolegroep, wat dui op ‘n meer
bevredigende antioksidantstatus. Hierdie resultaat is ook weerspieël in die feit dat totale
plasma antioksidantstatus (ORAC) in die rugby spelers oog geneig was om hoër te wees
as dié van die kontrole groep. Dit het ook geblyk dat MnSOD genotipe nie ‘n effek gehad
het op plasma vitamien C-, karotenoïed- of totale antioksidantstatus nie, met of sonder
kontrole vir dieet antioksidantinname. Die dieet vitamien C-, vitamien E-, karotenoïed- en
flavinoïedinname (vanaf voedsel en supplemente) was dieselfde vir rugby spelers en
kontrole en was toereikend vir beide groepe. Dit blyk dus dat dat die verband tussen
antioksidantstatus en MnSOD genotipe in die twee groepe nie beinvloed is deur
antioksidantinname nie. Ten slotte kan die gevolgtrekking gemaak word dat manlike rugby
spelers ‘n meer bevredigende antioksidant status het as onaktiwe manlike kontroles. Op
grond van hierdie gevolgtrekking word die algemene gebruik van antioksidant
supplemente deur atlete bevraagteken.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/19864 |
| Date | 03 1900 |
| Creators | Seele, Maria |
| Contributors | Senekal, M., Steyn, N.P., Stellenbosch University. Faculty of Science. Dept. of Physiological Sciences. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xiv, 173 leaves : ill. |
| Rights | Stellenbosch University |
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