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Determinants of serum 25-hydroxyvitamin D levels in healthy young adults living in the Western Cape

dc.contributor.advisorVisser, Janickeen_ZA
dc.contributor.advisorBlaauw, R.en_ZA
dc.contributor.authorKnight, Kimberleyen_ZA
dc.contributor.otherStellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Global Health. Human Nutrition.en_ZA
dc.date.accessioned2018-02-19T09:20:56Z
dc.date.accessioned2018-04-09T11:46:07Z
dc.date.available2018-02-19T09:20:56Z
dc.date.issued2018-03
dc.identifier.urihttp://hdl.handle.net/10019.1/103863
dc.descriptionThesis (MNutr)--Stellenbosch University, 2018.en_ZA
dc.description.abstractENGLISH SUMMARY : Background: The prevalence of vitamin D deficiency is fast emerging as a global pandemic. In South Africa, however, few studies have been conducted to determine the vitamin D status of the healthy population. While the effects of vitamin D on the body have been known for centuries, vitamin D has recently garnered great attention, with new evidence surrounding vitamin D and health emerging at a rapid rate. Previously thought to only be important for bone health, new research into the role of vitamin D in the body has revealed the importance of sufficient vitamin D levels for overall health. Aim: The main aim of this study was to investigate the vitamin D status of adults in the Western Cape. Objectives sought to determine whether skin tone, gender, basic anthropometrical measurements, diet, and lifestyle factors had an effect on serum 25(OH)D levels. Methods: This descriptive, cross-sectional study investigated the vitamin D status of healthy, undergraduate students (mean age: 20.41 ± 2.29 years) at Stellenbosch University. Serum 25(OH)D was collected and analysed, along with basic anthropometrical measurements (weight, height, BMI and waist circumference). A food frequency questionnaire was used to estimate dietary vitamin D intakes. Skin tone was measured using the Fitzpatrick Skin Type (FST) Classification, and a skin reflectometry device was used to measure dermal melanin content. Results: A total of 242 undergraduate students (with equal gender representation) were included in this study during September 2016. The results showed a mean serum 25(OH)D of 63.80 ± 41.35 ng/ml and a high prevalence of vitamin D sufficiency (90% of participants). The relationship between gender and serum 25(OH)D was found to be significant (p<0.01), with more females experiencing suboptimal vitamin D levels than males (18% vs. 5%). Just over half of the participants identified themselves as skin type IV when using the FST classification, and participants with lighter skin tones had higher levels of 25(OH)D than those with darker skin tones (p=0.02). The majority of the participants (60.74%) had normal BMIs, although the relationship between BMI and serum 25(OH)D was not statistically significant (p=0.09). Total mean dietary vitamin D intake was 7.99 ± 13.81mcg, with 87.2% of participants consuming less than the recommended daily intake of vitamin D (15mcg). The relationship between total vitamin D intake and serum 25(OH)D was found to be weak, but statistically significant (p=0.003). Sun exposure and lifestyle factors were not found to have an effect on serum 25(OH)D levels in this study. Conclusion: This study found a low prevalence of vitamin D deficiency amongst young adults, despite low dietary vitamin D intakes. Significant relationships were found between serum Stellenbosch 25(OH)D and gender, skin tone, and vitamin D intake. While this study population was homogenous, it encompassed a very specific group of young, healthy undergraduate students and further studies need to be done before the results are applied to the greater public.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING : Agtergrond: Die prevalensie van vitamien D tekort is vinnig besig om te groei tot ‘n globale pandemie. Beperkte aantal studies is al uitgevoer in Suid-Afrika om die vitamien D status van die gesonde populasie te bepaal. Alhoewel die effek van vitamien D op die liggaam al bekend is vir eeue, het vitamien D onlangs nuwe belangstelling gelok met nuwe inligting rakende vitamien D en gesondheid wat na vore kom. Voorheen was vitamien D bekend vir die verband met been gesondheid, terwyl onlangse navorsing die belang van voldoende vitamien D vlakke vir algehele gesondheid beklemtoon. Doel: Die hoofdoel van hierdie studie was om die vitamien D status van volwassenes in die Wes-Kaap te ondersoek. Addisionele doelwitte het die verband tussen velkleur, geslag, antropometriese metings, dieet en lewensstyl faktore op serum 25(OH)D vlakke ondersoek. Metodes: Hierdie dwarssnit, beskrywende studie het die vitamien D status van gesonde, voorgraadse studente (gemiddelde ouderdom 20.41±2.29 jaar) by die Universiteit van Stellenbosch bepaal. Serum 25(OH)D is versamel en bepaal, tesame met basiese antropometriese metings (gewig, lengte, LMI en middel omtrek). ‘n Voedselfrekwensie vraelys is gebruik om dieet vitamien D vlakke te bepaal. Velkleur is gemeet deur die Fitzpatrick Skin Type (FST) klassifikasie en ‘n vel reflektometer is gebruik om dermale melanieninhoud te meet. Resultate: 'n Totaal van 242 voorgraadse studente (gelyke geslagsverteenwoordiging) is ingesluit in hierdie studie gedurende September 2016. Die resultate het 'n gemiddelde serum 25(OH)D van 63.80 ± 41.35 ng/ml en 'n hoë voorkoms (90% van deelnemers) van voldoende vitamien D vlakke getoon. Die verwantskap tussen geslag en serum 25(OH)D was betekenisvol (p<0.01), met meer vrouens wat suboptimale vitamien D vlakke toon as mans (18% teenoor 5%). Net meer as die helfte van die deelnemers het hulself geïdentifiseer as veltipe IV deur die FST klassifikasie te gebruik. Deelnemers met ‘n ligter veltoon het hoër vlakke van 25(OH)D getoon as dié met ‘n donkerder veltoon (p=0.02). Die meerderheid van die deelnemers (60.74%) het normale LMI gehad, alhoewel die verhouding tussen LMI en serum 25(OH)D nie statisties betekenisvol was nie (p=0.09). Die totale gemiddelde dieet vitamien D inname was 7.99 ± 13.81mcg, met 87.2% van deelnemers wat minder as die aanbevole daaglikse inname van vitamien D (15mcg) inneem. Die verhouding tussen totale vitamien D inname en serum 25(OH)D was swak, maar statisties betekenisvol (p=0.03). Lewensstyl faktore en son blootstelling het nie ‘n effek op serum 25(OH)D gehad nie. Gevolgtrekking: Hierdie studie het 'n lae voorkoms van vitamien D tekort in jong volwassenes getoon, ten spyte van lae dieet vitamien D inname. Beduidende verhoudings was gevind tussen 25(OH)D en geslag, velkleur en vitamien D inname. Alhoewel hierdie studiepopulasie homogeen was het dit 'n baie spesifieke groep van jong, gesonde voorgraadse studente ingesluit en verdere studies moet gedoen word voordat die resultate toegepas kan word op die breë publiek.af_ZA
dc.format.extent189 pages ; illustrations, includes annexures
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch University
dc.subjectVitamin D in human nutrition -- Western Cape (South Africa)en_ZA
dc.subjectVitamin D deficiency -- Incidence -- Western Cape (South Africa)en_ZA
dc.subjectAdulthood -- Western Cape (South Africa)en_ZA
dc.subjectUCTD
dc.titleDeterminants of serum 25-hydroxyvitamin D levels in healthy young adults living in the Western Capeen_ZA
dc.typeThesisen_ZA
dc.description.versionMasters
dc.rights.holderStellenbosch University
dc.embargo.terms2020-12-01


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