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

  • J Visser Stellenbosch University
  • K Knight Stellenbosch University
  • L Philips Stellenbosch University
  • W Visser Stellenbosch University
  • M Wallace Cancer Association of South Africa (CANSA)
  • D G Nel Stellenbosch University
  • R Blaauw Stellenbosch University
Keywords: adults, healthy, summer and winter, Vitamin D, Western Cape

Abstract

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.

The full article is available at https://doi.org/10.1080/20786190.2019.1621047

Author Biographies

J Visser, Stellenbosch University

Division of Human Nutrition, Department of Global Health, Stellenbosch University, Cape Town, South Africa

K Knight, Stellenbosch University

Division of Human Nutrition, Department of Global Health, Stellenbosch University, Cape Town, South Africa

L Philips, Stellenbosch University

Division of Human Nutrition, Department of Global Health, Stellenbosch University, Cape Town, South Africa

W Visser, Stellenbosch University

Division of Dermatology, Stellenbosch University, Cape Town, South Africa

M Wallace, Cancer Association of South Africa (CANSA)

Cancer Association of South Africa (CANSA), Cape Town, South Africa

D G Nel, Stellenbosch University

Centre for Statistical Consultation, Stellenbosch University, Stellenbosch, South Africa

R Blaauw, Stellenbosch University

Division of Human Nutrition, Department of Global Health, Stellenbosch University, Cape Town, South Africa

Published
2019-09-04
Issue
Vol 61 No 4: July/August 2019
Section
Research Articles
By submitting manuscripts to SAFP, authors of original articles are assigning copyright to the South African Academy of Family Physicians. Copyright of review articles are assigned to the Publisher, Medpharm Publications (Pty) Ltd, unless otherwise specified. Authors may use their own work after publication without written permission, provided they acknowledge the original source. Individuals and academic institutions may freely copy and distribute articles published in SAFP for educational and research purposes without obtaining permission.