Research Articles

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

J. Visser, K. Knight, L. Philips, W. Visser, M. Wallace, D. G. Nel, R. Blaauw
South African Family Practice | Vol 61, No 4 : July/August| a4951 | DOI: | © 2019 J. Visser, K. Knight, L. Philips, W. Visser, M. Wallace, D. G. Nel, R. Blaauw | This work is licensed under CC Attribution 4.0
Submitted: 28 October 2019 | Published: 04 September 2019

About the author(s)

J. Visser, Stellenbosch University, South Africa
K. Knight, Stellenbosch University, South Africa
L. Philips, Stellenbosch University, South Africa
W. Visser, Stellenbosch University, South Africa
M. Wallace, Cancer Association of South Africa (CANSA), South Africa
D. G. Nel, Stellenbosch University, South Africa
R. Blaauw, Stellenbosch University, South Africa

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Background: Vitamin D deficiency is fast emerging as a global pandemic. In South Africa few studies have been conducted to determine the vitamin D status of the healthy population.
Methods: This prospective study with an analytical component investigated vitamin D status of healthy undergraduate students at two time points (winter and summer) at Stellenbosch University. Serum 25(OH)D was determined, anthropometric measurements taken and dietary vitamin D intake estimated (food-frequency questionnaire). Skin tone was determined (Fitzpatrick skin type classification), and a skin reflectometry device used to measure dermal melanin content.
Results: Results of 242 students indicated a mean serum 25(OH)D of 63.80 ± 41.35 ng/ml and a high prevalence of vitamin D sufficiency (88%). Significantly more females experienced suboptimal vitamin D levels than males (18 vs. 5%; p < 0.01). Participants with lighter skin tones had higher levels of 25(OH)D than those with darker skin tones (chi-square = 24.02; p = 0.02). The majority (60.74%) had a normal BMI, although there was no significant relationship between BMI and serum 25 (OH)D (Spearman’s r=–0.11; p = 0.09). Total mean dietary vitamin D intake was 7.99 ± 13.81 mcg, with 87.2% having inadequate intake (< 15 mcg). The relationship between total vitamin D intake and serum 25(OH)D was found to be significant in winter (p < 0.001) and summer (p = 0.01). Serum vitamin D levels were significantly higher in the winter phase (p < 0.001).
Conclusions: A low prevalence of vitamin D deficiency was found amongst healthy young adults, despite low dietary vitamin D intakes. Significant relationships were found between serum 25(OH)D and gender, skin tone and vitamin D intake. Further studies need to be conducted, especially in high-risk groups, before results are applied to the greater South African public.


adults; healthy; summer and winter; Vitamin D; Western Cape


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