Year
2022
Degree Name
Doctor of Philosophy
Department
School of Medical, Indigenous and Health Sciences
Abstract
Despite the essential role of vitamin D in calcium homeostasis, vitamin D deficiency is prevalent worldwide (2). This thesis aimed to determine levels of vitamin D deficiency and strengthen the evidence around the impact of skin type, diet and sun exposure on vitamin D status and associated musculoskeletal outcomes at varying latitudes.
A systematic literature review characterised the current vitamin D status of the African-Caribbean (AfC) population living at varying latitudes. Meta-analysis of the data extracted found this population to have sufficient (>50 nmol/L) 25(OH)D levels at 67.8 nmol/L, 95% CI (57.9, 7.6) but poor dietary intake of vitamin D at only 3.0μg/day, 95% CI (1.67,4.31). However, at high latitudes, the mean 25(OH)D was found to be insufficient at 40.9nmol/L, 95% CI (28.1, 53.7), confirming the need for further research at high latitudes.
The author built on this evidence review with a secondary analysis of the UK Biobank cohort to investigate the extent of vitamin D deficiency and dietary intakes of the AfC population in the largest sample of AfC individuals to date (n=4046). Over one third of this population were deficient (<25nmol/L), 47.1% were insufficient (25-50nmol/L) and 15.9% were sufficient (>50nmol/L). Median (IQR) 25(OH)D was insufficient at 30.0 (20.9) nmol/L.
Finally, a cross-country design was adopted to explore the impact of, skin type, diet, sun exposure and lifestyle factors on the vitamin D status of healthy females living in three different countries at varying latitudes (Wollongong, Australia: 34.42° S, Surrey, United Kingdom (UK): 51.24° N, and Sao Paulo, Brazil: 23.55° S). Two hundred and twenty females were included in the study of which 6% were vitamin D deficient (<25nmol/L), 15.1% were vitamin D insufficient (<50nmol/L), 48.2% were vitamin D sufficient and 30.3% had optimal vitamin D concentrations. Mean vitamin D intake was 3.4 ± 2.8μg/day for all participants, with 92% of participants having inadequate vitamin D intakes.
Overall, these findings show high levels of vitamin D deficiency at high latitudes. Country specific sunlight exposure recommendations are required, that take into environmental and personal factors, as well education around sources of dietary vitamin D.
Recommended Citation
Vearing, Rebecca, Vitamin DEED Study – Determinants of vitamin D status in women: the role of the environmental factors, ethnicity/skin type and diet, Doctor of Philosophy thesis, School of Medical, Indigenous and Health Sciences, University of Wollongong, 2022. https://ro.uow.edu.au/theses1/1763
FoR codes (2008)
1111 NUTRITION AND DIETETICS, 1117 PUBLIC HEALTH AND HEALTH SERVICES
Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.